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EXPECTATIONS FOR THE LABORATORY COMPONENT OF BSC1005C

The lab is a very important part of this course. The lab grade is a combined with the lecture grade

and contributes 30% to the final grade. You are advised to take the lab very seriously.

1. Attend lab every week. Attendance is important to your success. Nothing can replace

the experience acquired by actually doing the lab. If you miss a lab, you miss the quiz or

assignment for that lab as well as the information needed for the next week’s quiz or lab

report. A new lab is scheduled each week so that missed labs cannot be made up.

2. Answer the pre-lab questions. Usually we would have completed some of the topic in

lecture before the lab so you should be able to answer the questions or at least know

where to find the answers.

3. Since labs are only once per week it is easy to forget to do assignments and prepare for

lab quizzes. The best way to avoid this is to do the lab report as soon as possible after the

lab so that you can ask for help if you need it.

4. You will be assigned to a group for lab. Working in groups is an effective way of

learning because it allows students to share knowledge and learn from each other.

However, the lab report or lab quiz is an individual exercise. Do not allow any one to

copy your assignments and do not copy from any one. This is not ‘working together’.

Usually, in this case, one person comes up with an explanation and others copy it. It is

cheating, and very easy to detect when several students have the same grammatical and

factual errors! Any work that is copied will not receive a grade. This applies to both the

persons copying and those allowing their work to be copied.

5. Some time during the semester there will be a peer evaluation of the lab groups. That is,

you and each of your group members will have an opportunity to evaluate yourself and

each other on criteria such as cooperation, preparedness for lab etc.

I have read the above laboratory expectations and understand what is required of me.

Signature: ________________________________________ Date: ____________

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Laboratory Safety: General Guidelines

1. THE USE OF CELL PHONES IS STRITCLY PROHIBITED FOR THE DURATION OF THE

LAB PERIOD. STUDENTS USING CELL PHONES ARE CONSIDERD TO BE ABSENT!

2. Upon entering the laboratory, place all, books, coats, purses. Backpacks, etc in designated areas, not on

bench tops.

3. Locate and when appropriate, learn to use exits, fire extinguisher, fire blanket, chemical shower, eyewash,

first aid kit, broken glass container, and cleanup materials for spills.

4. In case of fire, evacuate the room and assemble outside the building.

5. Do not eat (includes gum), drink (not even water), or apply cosmetics in the laboratory.

6. Confine long hair, loose clothing, and dangling jewelry.

7. Wear shoes at all times in the laboratory.

8. Cover cuts and scrapes with a sterile, water-proof bandage before attending lab.

9. Wear eye protection when working with chemicals.

10. Do not taste anything or place anything into your mouth during the lab.

11. Wash skin immediately and thoroughly if contaminated by chemicals.

12. Do not perform unauthorized experiments.

13. Do not use equipment without instruction.

14. Do not remove anything from the lab.

15. Report all spills and accidents to your instructor immediately.

16. Never leave heat sources unattended.

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17. When using hot plates, note that there is not always visible sign that they are hot (such as a red glow).

Always assume that hot plates are hot.

18. Use an appropriate apparatus when handling hot glassware.

19. Do not allow liquid to come into contact with electrical cords. Handle electrical connectors with dry hand.

Do not attempt to disconnect equipment that crackles, snaps or smokes.

20. Upon completion of laboratory exercises replace all materials in the areas designated by your instructor.

21. Do not pick up broken glassware with your hands. Use a broom and dustpan and discard the glass in

designated glass waste containers; never discard with paper waste.

22. Leave the laboratory clean and organized for the next student.

I have read the above laboratory safety rules and regulations and agree to abide by them.

Signature: _________________________________________ Date: ____________

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EXERCISE 1

Metric Measurement & Scientific Notation

LEARNING OBJECTIVES

• Writing numbers in scientific notation.

• Use of the metric system to measure length, mass, volume and temperature.

• Conversion of metric units.

• Use of basic lab apparatus used for measurement

INTRODUCTION Science is the process of knowing and scientists are constantly making observation and making

measures to gain knowledge and describe various features of the world around us. Measurements

allow us to understand the relative size of structures. The metric system is the universal

measurement system used in all fields of science and is used to measure length, mass, volume

and temperature. Before we go on to the metric system let us first look at scientific notation.

SCIENTIFIC NOTATION

Scientific notation is a clear and concise way of writing very large or very small, cumbersome numbers that have many zeros. For example the distance from the earth to the sun is 149,600,000

kilometers and the size of a bacterial cell such as E. coli is 0.000000002 kilometers. Scientific

notation allows us to write these numbers in a much neater form. It is made up of one non-zero

number before the decimal point and multiplied by 10 (called the base), raised to a certain power

(called the exponent). An example of a number written in scientific notation is 1.25 x 104.

To write 149,600,000 km in scientific notation, we must first move the decimal point 8 places to

the left to obtain 1.496. (Note that where there is no decimal point, it is understood that it is after

the last digit of the number). Every time the decimal point is moved one place to the left, we are

dividing by 10, so moving it 8 places means we have divided by 100,000,000 or 108. Therefore

in order to preserve the original value of the number it must be multiplied by 108 and will be

written in scientific notation as 1.496 x 108. The exponent is the number of places moved. To

write 0.000000002 the same principle applies but this time the decimal point has to be moved 9

places to the right. Moving the point to the right means we are multiplying by 109. Therefore in

order to preserve the original value of the number it must be divided by 109, hence it will be

written as 2.0 x 10-9

in scientific notation.

General Rule: Move the decimal point enough places so that one non-zero number is in front

of the decimal point. The exponent is the number of places moved. The exponent is positive

when moved to the left and negative when moved to the right.

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Write the following numbers in scientific notation.

1) 800,000 ___________ 2) 123,000,000 ___________ 3) 0.00067 ___________

4) 0.00000000592___________ 5) 45,9000 ___________ 6) 0.0000732 ___________

Write the number represented by scientific notation.

7) 2.98 x 105 ___________ 8) 5.71 x 10

-4 ___________ 9) 6.7 x 10

-8 ___________

10) 3.9 x 103 ___________ 11) 2.56 x 10

2 ___________ 6) 8.24 x 10

4 ___________

METRIC SYSTEM CONVERSIONS

One of the greatest advantages of the metric system is the ease of conversion. It is a decimal

system of measurements and so it is easy to convert from one unit to the next either by

multiplying or diving by 10 or multiples of 10. This means that converting between units

requires only the movement of decimal places. The metric units for length, mass, and volume

are meters, grams, and liters, respectively. The same prefixes are used for all units. For

example, the prefix kilo denotes 1,000; 1 kilometer = 1000 meters, 1 kilogram = 1000 grams,

and 1 kiloliter = 1000 liters. Table 1 lists some common metric prefixes and their values.

Table 1 – Metric System Conversions.

Prefix Symbol Value Exponential equivalent

(scientific notation)

Giga G 1,000,000,000 109

Mega M 1,000,000 106

Kilo K 1,000 103

Hepta H 100 102

Deka D 10 101

Meter, liter, gram m, l, g 1 100

Deci d 0.1 10-1

Centi c 0.01 10-2

Milli m 0.001 10-3

Micro µ 0.000001 10-6

Nano n 0.000000001 10-9

To convert from one metric unit to another subtract the exponents, i.e.(the from exponent minus the to

exponent) . For example to convert from Kg to mg:

Kg =103 mg = 10

-3

3- (

-3) =

6

6

The difference between the exponents determines how many places the decimal will be moved. If you are

converting from a larger metric unit to a smaller metric unit the difference between the exponents will be

positive. Therefore the decimal point is moved to the right. So to convert from 65 kg to mg, the decimal

point is moved six places to the right. The result will be 65, 000, 000 mg.

If you are converting from a smaller metric unit to a larger metric unit the difference between the

exponents will be negative. Therefore the decimal point is moved to the left.

For example, to convert from 97 Kg to Mg: Kg = 103 Mg = 10

6

3-(

6) =

-3

The point is moved three places to the left. The result is 0.097Mg

Another example: To convert from 853 µg to cg: ug =10-6

cg = 10-2

-6-

(-2

) = -4

The point is moved four decimal places to the left. The result will be 0.0853 cg.

Complete the following metric conversions.

13) 28nm = ___________ mm 14) 462g = ___________ kg 15) 51ml = ___________ kl

16) 8dm = ___________ m 17) 9837 kg = ___________ mg 18) 36 mm = ___________ dm

19) 6Gm = ___________ m 20) 1763nm = ___________ cm

METRIC MEASUREMENTS (LENGTH)

The metric unit for measuring length is the meter. In this exercise, you will measure the length

of various objects.

Procedure

1. Measure the length of the following objects in the units indicated:

Your index finger (cm)

Diameter of a penny (mm)

Height of your lab partner (m)

2. Area is calculated by multiplying the length x width. Measure the length and width of

your driver’s license in centimeters and the lab table in meters and find their areas.

Always record the units when you make a measurement.

Length Width Area

Driver’s license

Lab table

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3. Select three small wooden blocks. Measure the length, width, and height of each block in cm

and record those values below. Volume is calculated by multiplying length x width x height.

Calculate the volumes of the 3 blocks.

Block # Length Width Height Volume

1 ___________ x ___________ x ___________ = ___________

2 ___________ x ___________ x ___________ = ___________

3 ___________ x ___________ x ___________ = ___________

METRIC MEASUREMENTS (VOLUME)

Volume is typically measured in units termed liters. However it can be measured in cubic

centimeters (cm3 or cc). One cubic cm equals 1 milliliter. (1cm

3 or cc = 1ml.)

Procedure

1. Using the data collected in the previous section, calculate the volume of each of the three

blocks in ml and record the data below.

Volume of block 1___________ ml block 2 ___________ ml block 3 ___________ ml

Graduated cylinders are used in the laboratory to measure small amounts of liquid.

Obtain 3 graduated cylinders, a beaker, a test tube and a cuvette.

Note: When water is placed into a graduated cylinder or other container, it begins to climb the

sides of the container by cohesion and adhesion. Cohesion is the tendency of water molecules to

stick to each other and adhesion is the way they cling to the side of the glass container. The water

level inside the container is uneven. This is termed the meniscus. The correct volume should be

read at the lowest margin of the water level.

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2. Fill the beaker up to the 200ml mark and pour the water into the graduated cylinder.

What is the volume? ___________ . This discrepancy tells us that the beaker can be used

to give approximate amounts of a liquid. For accuracy and precision in the

measurement of liquid, the graduated cylinder must be used.

3. Use the graduated cylinders to find the volume of the test tube, the cuvette and the

completely full beaker.

Test tube

Cuvette

Beaker

Volume of cube-shaped object can be determined by measuring length, width, and height and

multiplying these together. The volume of irregularly shaped objects, like a screw, can not be

measured in this way. Another technique, known as water displacement, permits volumes of all

objects to be calculated.

4. Measure the volume the three irregularly shaped objects using water displacement.

Place some water into the graduated cylinder. Note the amount. This is your initial volume.

Gently place the object into the graduated cylinder so that there is no splashing or loss of water.

The level of the water will rise. Note the new level. This is your final volume. Subtract the

initial volume from the final to get the volume of your object in ml.

Initial volume Final volume Volume of object

Object 1

Object 2

Object 3

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METRIC MEASUREMENTS (MASS)

Mass is a measure of the amount of matter that an object has. Mass differs from weight in that

weight is the force gravity exerts on an object. Therefore, the mass of an object stays constant,

but weight can change if gravity changes. For example, the moon’s gravity is roughly 1/6 that of

the earth’s. A person weight 180 lbs. on earth would weigh 30 lbs. on the moon. Since mass is

constant, a person with a mass of 82 kg would have that mass on earth or on the moon.

The Density of a material is calculated by the dividing the mass by the volume. (D=M/V)

The mass is always measured in grams and the volume in ml (cc).

Procedure

1. Using a triple-beam balance, calculate the mass of the three objects indicated.

Mass (g) Volume (ml) Density (g/ml)

METRIC MEASUREMENTS (TEMPERATURE)

Scientists measure temperature using the Celsius or centigrade scale, which is based upon the

freezing and boiling points of water. The Fahrenheit scale is not used in science. Water freezes

at 0°C (32°F) and boils at 100°C (212°F).

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Converting from Fahrenheit to Celsius requires using the following equation:

°C = 5/9 x (°F – 32) or °C = 0.56 x (°F – 32)

Converting from Celsius to Fahrenheit requires using the following equation:

°F = (9/5 x °C) + 32 or °F = (1.8 x °C) + 32

Procedure

Using the Celsius thermometer provided, measure the temperature of the following and then use

the equation above to convert each into Fahrenheit.

Temp. in Celsius Temp. in Fahrenheit

Room temperature ______________ ______________

Surface of skin ______________ ______________

Ice water in beaker ______________ ______________

Boiling water ______________ ______________

Tap water ______________ ______________

Today’s temperature _______________ ______________

PRACTICE PROBLEMS

Complete the following problems.

Write the following numbers in scientific notation.

1) 7000 ___________ 2) 51,800___________ 3) 465,000,000 ___________

4) 8,000,000 ___________ 5) 234,000 ___________ 6) 0.000003 ___________

7) 0.0089 ___________ 8) 0.00000239 ___________ 9) 0.0045 ___________

10) 567,000,000 ___________

Write out the numbers represented by scientific notation.

11) 8.0 x 103 ___________ 12) 4.23 x 10

8 ___________

13) 9.21 x 10-4

___________ 14) 9.27 x 10-9

___________

15) 1.5 x 104___________

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Complete the following metric conversions.

16) 4.5 cm ___________ mm 17) 63 kg ___________g 18) 28.6 l ___________ml

19) 1.45 mm ___________ cm 20) 98.2 nm ___________mm 21) 7.8 g ___________ mg

22) 89.2 ml ___________ l 23) 34.8 nm ___________ cm 24) 28.5 cm ___________km

25) 78.9 km ___________ m 26) 30.6 cm ___________ mm 27) 45.0 nm ___________mm

28) 23.8 kg ___________mg 29) 76 ml ___________ l 30) 58.5 g ___________mg

Metric Conversions

Metric to American

Standard

American Standard

to Metric

Length

1 mm = 0.039 inches

1 cm = 0.394 inches

1 m = 3.28 feet

1 m = 1.09 yards

1 inch = 2.54 cm

1 foot = 0.305 m

1 yard = 0.914 m

1 mile = 1.61 km

Volume

1 ml = 0.0338 fluid ounces

1 L = 4.23 cups

1L = 2.11 pints

1L = 1.06 quarts

1L = 0.264 gallons

1 fluid ounce = 29.6 ml

1 cup = 237 ml

l pint = 0.474 L

1 quart = 0.947 L

1 gallon = 3.79 L

Mass

1 mg = 0.0000353 ounces

1 g = 0.0353 ounces

1 kg = 2.21 pounds

1 ounce = 28.3 g

1 pound = 0.454 kg

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Temperature

To convert temperature:

°C = �

� (F – 32)

°F = �

� C +32

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EXERCISE 2

pH AND BUFFERS

LEARNING OBJECTIVES:

• Become familiar with the pH scale.

• Determine the pH of different substances using a pH indicator.

• Learn to use the pH meter.

• Determine experimentally which antacid works best at neutralizing excess stomach acid.

Introduction

pH (potential of hydrogen) is a measure of the free hydrogen ions (H+) in a solution. Pure

water is called a neutral solution because it has equal numbers of the positively charged H+

ions and the negatively charged hydroxide ions (OH-). An acid has more H+ ions than OH-

ions while a base (also called an alkali) has fewer H+ ions than OH- ions. Although most of

the areas of our body tend to be in the neutral range e.g. the pH of blood is between 7.3 and

7.5. pH buffers present in our cells keep the pH within the neutral range. However, the pH

of the stomach is very low, between pH 1.0 and 3.0. The pH scale is used to measure pH of

a solution and ranges from 1 to 14, with a pH of 1 being the most acidic and a pH of 14 the

most basic. Refer to the pH scale below.

Figure 1 pH scale.

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PART A: MEASURING PH

pH Indicators

pH indicators are chemicals, which display characteristic color changes in response to the

pH of standard buffer solutions. Some pH indicators used in the lab are: litmus,

phenolphthalein, methyl red, and phenol red, to name a few. These are available in liquid

form as well as paper strips. Hydrion (a type of so-called universal indicator) is one such

paper indicator that will allow you to read from pH 1 to 14. To read the pH, compare the

color change to the color chart provided.

Procedure

Using only the pipette in the beaker containing the substance to be tested, place a few

milliliters of the solution into a watch glass. (DO NOT SWAP PIPETTES). Dip a small

strip of the pH indicator into it and observe the color change. Match the color of the

indicator paper with the color chart and record the pH.

Record your results in the table below.

Table 1: pH of some common substances

Substance pH Acidic or Basic?

Ammonia solution

Aspirin solution

Baking soda

Banana

Bleach

Coffee

Detergent

Distilled water

Milk

Milk of magnesia

Lemon juice

Orange juice

Soda pop

Vinegar

15

pH meters

pH indicator s give us a general idea of the pH of the solution. To get a more accurate

reading of the pH, an instrument called a pH meter can be used. It makes use of an

electrode, which is immersed into the solution to be measured, and the pH is registered on a

monitor.

Use the pH meter to measure the pH of solutions X and Y.

pH indicator paper pH meter Acidic or basic?

pH of X

pH of Y

PART B: EVALUATING SOME ANTACIDS

Introduction

The very acidic condition in the stomach aids in the digestion of food. Sometimes the

stomach produces too much acid, which can cause discomfort. A common remedy is to

chew an antacid tablet. Antacids work by neutralizing excess hydrogen ions and are thus,

considered buffers. A buffer is any substance that can remove or accept hydrogen ions in

order to stabilize the pH of a solution.

In this experiment you are going to evaluate 4 different antacids is to determine which one

works best at neutralizing excess stomach acid. We will use an acid solution of the same

pH as stomach acid.

Procedure

1. Use a mortar and pestle and grind up about 3 tablets of antacid.

2. Weigh out 4 grams of antacid powder.

3. Use a measuring cylinder, measure out 200ml of acid solution and pour the acid

into a 400ml beaker.

4. Take the beaker containing the acid to the pH meter. Start the magnetic stirrer. You

will need a timing device.

5. Immerse the electrode into your acid solution, making sure that it is in the solution

and not in the vortex created by the stirrer.

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6. Allow the pH meter to read ‘stable’ then record the pH of the acid solution. This is

your initial or starting pH.

7. Pour the antacid powder into the acid solution. Start timing as soon as you begin

to add the powder.

8. Record the final pH (when the pH meter reads ‘stable’ again) and the time taken to

get to that pH.

9. Rinse the electrode of the pH meter thoroughly with distilled water. (Handle with

care!). Leave the electrode immersed in the storage solution.

10. Wash the mortar and pestle and dry well.

11. Repeat the experiment for the other antacids.

12. Record your results in the table below.

Antacid Initial pH Final pH Difference in pH units Time elapsed

(minutes)

Lab Report

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pH AND BUFFERS

1. From your results, what is the difference in the H+ content between lemon juice and

household ammonia?

___________________

From your results in Table 1, rank the following in order of their H+ content (from

the one with the most H+ ions to the one with the least).

Lemon juice, orange juice, milk, distilled water, coffee, baking soda, ammonia.

Most H+ ions

Least H+ ions

2. Use your results from the antacid experiment to answer the following questions.

Antacid Initial pH Final pH

Difference in

pH units

Time

elapsed

Rate of acid

neutralization/

pH units per

minute

a. Calculate the rate of acid reduction by each of the antacids and record your

results in the table above.

b. At the end of the experiment which antacid solution still had the highest

number of H+ ions? ________________

c. At the end of the experiment which antacid solution had the lowest number

of H+ ions? ___________________

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d. Which antacid neutralized the acid slowest? (rate!) ____________________

e. Which antacid neutralization the acid fastest? (rate!) ___________________

3. Suggest one reason why this method may not be ideal for comparing all antacids.

___________________________________________________________________

___________________________________________________________________

4. State five variables that must be kept constant (the same) in this experiment.

_______________________________________

_______________________________________

_______________________________________

_______________________________________

_______________________________________

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EXERCISE 3

Carbon Compounds

LEARNING OBJECTIVES

• Perform diagnostic tests to detect the presence of reducing sugars (Benedict’s), starch (Lugol’s), protein (Biuret), lipid (SudanIV) and sodium chloride (silver

nitrate).

• Identify which substances are present in an unknown mixture using these

diagnostic tests.

INTRODUCTION

The organic molecules of life are carbohydrates, lipids, proteins and nucleic acids. Each

of these groups of molecules is responsible for specific important roles in living cells.

Give 2 functions of each of these compounds in living cells:

Carbohydrates

________________________________________________________________________

________________________________________________________________________

Lipids

________________________________________________________________________

________________________________________________________________________

Proteins

________________________________________________________________________

________________________________________________________________________

Nucleic acids

In this exercise some simple chemical tests will be used to identify the presence of

members of these groups of organic compounds. (There are no simple tests for nucleic

acids that we can perform in this lab).

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CARBOHYDRATES

Three types of carbohydrates are commonly founding living cells: monosaccharides,

disaccharides and polysaccharides.

Give an example of each type:

Monosaccharide__________________________

Disaccharide_____________________________

Polysaccharide____________________________

Some monosaccharides are called reducing sugars. They react with a blue reagent called

Benedict’s solution to form a colored precipitate (a solid that settles out of the solution)

Sugars that do not react with Benedict’s are called non-reducing sugars. Polysaccharides

do not react with Benedict’s, but will react with another reagent called Lugol’s iodine.

TESTS FOR CARBOHYDRATES

1. Benedict's Test for Reducing Sugars

In the Benedict's test, the sample is heated with the Benedict's reagent. If

reducing sugar the precipitate forms. The color of the precipitate can range from

green, to yellow, orange, red or brown. The color depends on the amount of

reducing sugar present in the sample, with brown being the most concentrated.

Procedure

1. Mark a clean test tube to identify the sample being tested.

2. Add 2 ml of the sample and 2 ml of Benedict’s reagent in the tube.

Record the color of the solution in the tube. This is your initial color.

3. Heat the tubes in a hot bath. Remove the tubes in which the color

changes. If there is no immediate color change, allow the tube to

heat for 5 minutes.

4. Record results in Table 1 below.

Table 1 – Results of Benedict’s for reducing sugars.

1 2 3 4 5 6 7 8 9 10 11

Water Starch Glucose Nutra- Sweet

Sucrose Onion juice

Potato slice

Milk Fructose solution

Apple juice

Honey

Initial color

Final color

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Explain in your own words why some of the colors changed after heating the solutions and

why others did not.

_________________________________________________________________________

_________________________________________________________________________

Why is it important to have a tube with just water in it?

_________________________________________________________________________

Sucrose is a sugar. Why did it not form a precipitate with Benedict’s?

_________________________________________________________________________

2. Lugol’s Iodine Test for Starch

Starch reacts with Lugol's Iodine solution (iodine-potassium iodide, I-KI) to

produce a complex of starch and iodine with an intense blue or black color.

Procedure

1. Obtain a clean white spot plate.

2. Place one drop of the sample solution in a depression in the spot plate.

Use a small piece if it is a solid. Your initial color is the color before you

add the Lugol’s.

3. Add one drop of Lugol's I-KI solution to the drop of sample.

4. Note any color change.

5. Record results on Table 2 below.

Table 2 – Results of Lugol’s test for starch

1 2 3 4 5 6 7 8 9 10 11

Water Starch Glucose Rice Sucrose Onion juice

Potato slice

Milk Pasta Bread Yuca

Initial color

Final color

22

Why did some of these chemicals react with the Lugol’s iodine and others did not?

_________________________________________________________________________

_________________________________________________________________________

Which substance is your positive control? Negative control?

_________________________________________________________________________

LIPIDS

Lipids e.g. fats, are compounds that are non-soluble in water (non-polar). They also tend

to be less dense that water and so will float on it. Triglycerides are the most common

form of fats found in nature and are made up of glycerol and three fatty acids.

What does the term hydrophobic mean?________________________________________

How do saturated lipids differ from unsaturated lipids?

_______________________________________________________________________

_______________________________________________________________________

Sudan IV Test for Lipids

Sudan IV is a dye that will dissolve only in non-polar solvents, such as oily

hydrocarbons or lipids. If a liquid is mixed with Sudan IV dye and the solution turns

red then it can be assumed that the liquid was a lipid or hydrocarbon. Typically this

would be an oil, but Sudan IV will also dissolve in non-oily hydrocarbons such as

acetone and alcohol. The Sudan IV reagent that you will use has been dissolved in

alcohol to make it easy for you to handle. If fat is present in any of the substances you

test, the Sudan IV will dye it red and it will be seen floating as a red layer.

Procedure

1. Mark a clean test tube to identify the sample being tested.

2. Add 2 ml of the following substances to each tube.

Water

Vegetable oil

Hamburger juice

Salad dressing

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3. Add 2 ml of water to each tube.

4. Add five drops of the Sudan IV solution.

5. Mix each tube by agitating from side to side.

6. Record results in Table 3 below.

Table 3 – Results of Sudan IV test for fats.

Water Vegetable Oil Hamburger juice Salad dressing

Positive

red layer?

What do your results tell you about each of the samples you have tested?

_________________________________________________________________________

_________________________________________________________________________

PROTEINS

Proteins are the most abundant of all the organic molecules found in the cell. They are

made up of amino acids which are bonded together by peptide bonds to form chains

called polypeptides.

Biuret Test for Proteins

The Biuret reagent reacts with peptide bonds and so is an indication of the presence

of proteins. Biuret is sensitive to even a few peptide bonds. Consequently, when

Biuret reagent is mixed with a solution containing proteins (with many peptide

bonds) a strong reaction occurs that produces a violet color. Because the Biuret

reagent is blue, it is sometime necessary to look carefully to make sure that the

reaction mixture is actually violet or purple and not just an intense blue. Holding the

solution against a white background may be helpful.

Procedure

1. Mark a clean test tube to identify the sample being tested.

2. Add 1 ml of the sample to the tube followed by 2 ml of Biuret reagent.

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3. Place a piece of parafilm over the mouth of the test tube with your

thumb over it and shake vigorously.

4. Allow the tube to sit at room temperature for 3 minutes.

5. Note any color change.

6. Record results in Table 4 below.

Table 4 – Results of Biuret test for protein.

Distilled

water

Egg

albumin

Milk Hamburger

juice

Amino

acid

Gelatin

Color

present

Protein

present

Which sample do you think contained the most protein? Why?

_________________________________________________________________________

What was the final color of the amino acid sample? Explain why.

________________________________________________________________________

_________________________________________________________________________

SODIUM CHLORIDE

Sodium chloride is an inorganic substance and is very important in living cells.

Silver Nitrate Test for Salts The silver nitrate reagent is a mixture of silver nitrate with dilute nitric acid. Handle

this solution with care! If any gets on your skin wash immediately with lots of water.

The skin areas contacted by silver nitrate solution will darken but will return to

normal in about a day. Minor exposure of this type is not harmful.

Silver test detects the presence of certain chloride ions. As chloride ions are most

commonly encountered in water solutions (e.g. sodium chloride is sea salt/table

salt), we will be looking manly for chloride ions as an indication of salt.

The addition of a few drops of silver nitrate reagent to a water solution will

immediately produce a milky-white precipitate which will be intense and persistent

if the solution has a significant concentration of chloride ions. If no precipitate

whatsoever is seen, the solution must have a solute free of chloride ions.

25

Procedure

1. Mark a clean test tube to identify the sample being tested.

2. Place l ml of the sample into the test tube.

3. While carefully observing the tube, add 2 drops of the silver nitrate

reagent to the sample. (Note the possible formation of a white

precipitate. The precipitate may or may not form and may or may

not persist, depending on the concentration of ions. If chloride ions

are abundant, the white precipitate will persist and make the sample

cloudy).

4. Record results in Table 5 below.

Table 5 – Results of test silver nitrate test for chloride ions.

Water Salt

solution

Salad

dressing

Meat

juice

Starch Albumin Apple

juice

White

precipitate?

Lab Report

CARBON COMPOUNDS LAB DATA SHEET

1. Use this sheet to summarize the results of all your tests. Use the symbols shown. (If

you did not perform the test on a substance leave the box blank).

Positive: + Negative: –

Sample

Benedict’s

test Biuret test

Lugol’s

Iodine test Sudan IV test

Silver Nitrate

test

Distilled water

Albumin

Amino acid

Apple juice

Bread

Fructose solution

Gelatin

Glucose solution

Honey

Meat juice

26

Milk

NutraSweet

Onion juice

Pasta

Potato

Rice

Salad dressing

Sodium chloride

Starch solution

Sucrose solution

Vegetable oil

Yuca

Unknown # A

Unknown # B

Unknown # C

27

2. Summarize the tests you performed in the table below:

Test Reagent used Description of positive result

Reducing sugar

Starch

Lipid

Protein

3. Why was a water sample included with each test?

___________________________________________________________________

28

EXERCISE 4

Microscopy & Cells

LEARNING OBJECTIVES

• Learn to use a compound microscope

• Make basic slide preparations (wet mounts).

• Distinguish between plant and animal cells based on microscopic observations of their

structures.

• Microscopic observation of bacterial cells

• Observation of some other eukaryotic cells: microscopic algae and protists.

Answer these questions before you come to lab:

1. What are the three components of the cell doctrine?

___________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

2. Name the two types of cells found in the living world.

__________________________

__________________________

3. State three differences between these types of cells

_________________________________________________________________

_________________________________________________________________

_________________________________________________________________

4. State the four structures that are common to all cells.

_______________________

_______________________

_______________________

_______________________

29

5. State three differences between plant and animal cells.

______________________________ ________________________________

______________________________

PART 1: THE COMPOUND MICROSCOPE

Care and maintenance of a microscope

• Always treat your microscope with care. When moving the microscope, use two hands.

Grasp the arm of the microscope with one hand and support the base with the other

hand. Do not swing it!

• The lens surfaces must be treated with great care, as they can easily be scratched or

chipped. Use ONLY lens paper to remove dust if needed. NEVER use paper towels,

handkerchiefs, shirt tails, Kleenex, alcohol, or blow moist air onto any lens as a way

of cleaning it.

• At the higher magnifications, always refocus with the fine adjustment only. Never use the coarse adjustment at high power. If you do, you run the risk of smashing the

objective into the slide and causing irreparable damage to both! Course adjustment

should only be used during initial focusing with the low power objective.

• Do not force anything-lenses, knobs, levers- ask for help.

• Before storing the microscope, turn the objectives to the lowest power. Clean all

lenses with lens paper. Remove all slides from the stage. Secure the power cord, and

replace the microscope in the cabinet with the eyepieces facing inwards.

30

A. Identifying the Parts of the Microscope

This type of microscope is called a compound light microscope. Compound, because it uses

two lenses to magnify and show details of specimens that are too small to observe with the

naked eye. The purpose of a microscope is mainly magnification. One of the lenses is in

the eyepiece and the other is the objective lens. The microscope uses light as the

source of illumination of the specimen.

Locate all the parts of the microscope as your instructor describes them:

Eyepieces: The eyepiece contains the ocular lens system and is one of the two lenses used

for magnification. Engraved on the side of the ocular lens you will see its

magnification. What is the magnification of your ocular lens system? _____

Nosepiece: This is a revolving circular mechanism that holds the different objective lenses.

Rotating the nosepiece changes the objective lens. The objective lens is in place when it is directly

over the stage and you will hear a click when it is in place.

Objective lenses: T h e s e a r e i n d i v i d u a l l e n s e s a t t a c h e d t o t h e n o s e p i e c e . A

magnification number is indicated on each objective lens. Your objective magnification values

are ________________, ______________, _______________, and______________.

Total Magnification: To obtain the total magnification produced by both the objective and

ocular lenses, you simply multiply the two values.

Eyepiece

Magnification

Objective Lens

Magnification

Total

Magnification

X Scanning X X

X Low power X X

X High power X X

X Oil immersion X X

Note: The oil immersion lens is not used in an introductory biology lab. DO NOT ATTEMPT

TO USE IT AND DO NOT PUT IT IN PLACE.

Stage: Also called the mechanical stage. This is the surface that supports and secures the slide

with the help of the stage clips.

Stage Controls: these are usually located on the side of the stage. Front/back controls move the

slide front to back and vice versa. Side/side controls move the slide from side to side.

Condenser: This is located under the stage and focuses the light form the lamp through a hole in

the stage and onto the specimen. It can be used to adjust the quality and amount of light passing

through the specimen. There is a condenser adjustment knob that may be used to raise or lower

the condenser.

31

Iris diaphragm: Located under the condenser, this is used to adjust the intensity of light passing

through the specimen. It is opened or closed using the iris diaphragm lever.

Coarse-Adjustment Knob: This large knob, located on the arm, adjusts the distance between

the stage and the objective lens in large increments. It is used initially to bring the specimen into

focus. It is dangerous to use this knob when the objective lens is already near the slide. It should

be turned very slowly to avoid breaking the slide.

Fine-Adjustment Knob: This is the small knob attached to the coarse-adjustment knob. It

adjusts the distance between the stage and the objective in small increments. It is typically used

after the objective lens is already near the slide and the specimen is almost in focus. It should be

turned very slowly to avoid breaking the slide.

Lamp: Light source located under the condenser. There is a switch to turn it on and off.

Rheostat: Regulates the intensity of the light (‘light dimmer’).

B. Label the parts of the microscope:

32

C. Learning to focus the microscope

1. Plug in the microscope, turn on the light, open the iris diaphragm and raise the condenser.

Rotate the nosepiece so that the scanning objective (4X) is in place over the stage.

2. Obtain a prepared slide of the letter e.

3. Place the slide on the stage so that the label is on your left. What is the orientation of the

e? Is it upside down or the right way it? (Look at it on the stage on, we are not looking down the microscope yet).

4. Using the stage controls, move the slide so that the e is directly in the center of the circle

of light.

5. Using the coarse adjustment, while looking down the microscope through the eyepiece

(use both eyes), bring the stage up towards the objective until you can see the e. Bring it

into as sharp a focus as you can with the coarse adjustment knob and then fine tune with

the fine adjustment knob.

6. What is the orientation of the e now? Move the slide to the right. Which way does it

appear to move? This is called inversion and refers to the fact that the image you see

under the microscope is not only inverted but also reversed.

Sketch the e in the space below: Magnification?

7. Increasing magnification: The system of objectives is constructed so that they

are parfocal. Parfocal means that an object remains relatively in focus when you

change objectives. The area of the microscope slide that can be viewed through the

microscope is the field of view. When you switch from a lower magnification

objective to a higher magnification objective, the size of your field of view under the

microscope is greatly reduced. Therefore, always center the object under observation in

your microscope field of view before changing objectives. This will reduce the

chances that you "lose" your specimen somewhere outside the field of view. Note:

The greater the magnification, the smaller the field of view.

33

8. Move your e until it is centered in the field of view and in focus, with the 4X

objective in place. Next, carefully rotate the nosepiece until the l o w p o w e r ( 10X)

objective is in place. Focus.

Sketch its appearance in the space provided: Magnification?

9. Center the e again and move the nosepiece so that the high power (40X) is in place.

Focus. What is the magnification of your specimen? Describe what you see and explain

why this is all that you can see at this magnification.

_________________________________________________________________________________

_________________________________________________________________________________

10. Depth of focus: Obtain a slide o colored threads. Find a point with the low power

where the threads intersect. Slowly focus up and down. Notice that when one thread is in

focus, the others seem blurred. The vertical distance that remains in focus at one time is

called the depth of focus. Switch to high power and notice that the depth of focus is more

shallow (decreases) with high power than with low power. Determine the order to the

threads and complete the chart below.

Order of threads

Depth Thread color

Top

Middle

bottom

PART 2: OBSERVATION OF CELL STRUCTURE

Now that we know how to use the microscope we will use it to observe some different types of

cells. Many of the organelles in cells are much too small to be seen with the magnifications

34

available on these microscopes. Observe and record all of the structures that you can see in each

of the cells. Also note any differences between the cells that you observe. To view the cells

under the microscope we first have to place the specimen on a slide by making a temporary wet

mount.

Exercise 1: Plant Cells

Making a Temporary Wet Mount of Elodea (water plant)

1. Place a drop of water in the center of a microscope slide.

2. Using tweezers pick up a leaf of Elodea and place it in the drop of water.

3. Hold a cover slip between your thumb and index finger to one side of the specimen

at about a 45° angle. Slide the cover slip toward the drop of water and specimen

until it contacts the drop of water.

4. Gently lower the cover slip onto the specimen and the drop of water, trying to avoid

large air bubbles. Air bubbles appear as black rings under the microscope and are

often mistaken for something more exciting! More water may be added at the edge of

the cover slip if needed to fill in any air spaces.

5. The specimen is now ready to place on stage for observation with the microscope.

6. View under all magnifications, starting with 4X.

7. Sketch what you observe under 100X or 400 X total magnifications in the space below.

You only need to draw four or five cells accurately.

Label the cell wall, chloroplasts, and the cytoplasm.

35

100X 400X

Onion cells

1. Make a temporary wet mount of sma ll p ie ce of onion skin. U se s k in on ly d o

n o t i n c lu de a n y o f t h e t i s sue f r om th e on ion . T he thinner your specimen,

the better the cells will be seen. Use a drop of iodine to make the mount.

2. Sketch what you observe under 100X or 400 X total magnifications in the space below.

You only need to draw four or five cells accurately.

Label the cell wall, cytoplasm, and the nucleus.

100X 400X

How are these two kinds of plant cells different?

________________________________________________________________________

________________________________________________________________________

How are they the same?

36

________________________________________________________________________

________________________________________________________________________

Why are chloroplasts absent in the red onion cells?

__________________________________________________________________________

Exercise 2: Human cheek cells

1. Gently scrape the inside of your mouth with a toothpick to obtain epithelial

cells.

2. Swirl the toothpick in a drop of drop of methylene blue on a clean slide.

3. (Dispose of toothpick and cheek cell slide in the disinfectant solution.)

4. Carefully add a cover slip as described above and examine the mount at all levels

of

magnification.

5. Draw four or five cells at highest magnification, labeling the cell membrane,

cytoplasm, and nucleus.

400X

How are these cells similar to and different from the onion cells and the Elodea cells?

______________________________________________________________________

______________________________________________________________________

______________________________________________________________________

37

Exercise 3: Prokaryotic Cells-Bacteria

Prokaryotic cells, for example, bacteria are extremely small ranging in size from lµ to

20µ.

(How many micrometers (µ) are there in 1 millimeter? ______________)

Like, plants most bacteria possess a rigid cell wall that surrounds the cell membrane and

helps the cell maintain its shape and prevents it from bursting. Inside the cell membrane, the

cytoplasm contains ribosomes, DNA region, and storage granules. However, they have no

membrane-bound organelles like eukaryotic cells.

Bacteria are often classified according to their shape:

1. Coccus (spherical cells): Streptococci, which consist of chains of spherical cells, are

associated with strep throat. (plural, cocci)

2. Bacillus (rod-shaped): Escherichia coli, found in the intestines of humans.

3. Spirillum (spiral-shaped): Borrelia burgdorferi, cause of lyme disease.

Since bacteria are so small in order to view them we have to magnify them 1000x. Observe

the demonstration microscopes and draw the shapes of the bacterial cells below.

Coccus 1000x Bacillus1000x Spirillum 1000x

Exercise 4: Survey mixture

Place a drop of the mixture o f mi c r o s c o p i c a l ga e on a slide with a cover slip and

observe. Sketch the appearance of three different types of cells and identify them using the

chart provided.

38

REVIEW QUESTIONS

1. What happens to the field of view and depth of field when you increase

magnification?

____________________________________________________________

2. If the ocular had a magnifying power of 10X and the objective had a magnifying

power of l0X, what would be the total magnification of an object viewed through

these lenses be?

________________________

3. Why is it necessary to center the specimen in the field of view before switching to a

higher power objective lens?

__________________________________________________________________

4. Which adjustment knob is never used with the high power objective in place (fine or

coarse)? _______________________

Why not? ____________________________________________________________

5. List four things you should do before putting away your microscope away.

_____________________________________________________________

_____________________________________________________________

_____________________________________________________________

_____________________________________________________________

6. Which organelles d i d yo u s e e with the magnification available?

_______________________________________________________________

7. You are trying to view a specimen under the microscope and have the following

problems. Describe specifically how you would adjust the microscope to get a better

view of the specimen in each case:

There is not enough light

___________________________________________________________________

The specimen is blurred

39

____________________________________________________________________

The specimen is not in the center of the field of view

_____________________________________________________________________

8. From your observations, give 3 differences between a cell of Elodea and an onion

cell.

Use comparable features!

Elodea cell Onion cell

i.

ii.

iii.

9. Give 3 differences (observed) between the Elodea cell and the cheek cell.

Elodea cell Cheek cell

i.

ii.

iii.

40

10. Why did we have to use the 100X objective to view the bacterial cells but not

the others?

EXERCISE 5

Enzymes

LEARNING OBJECTIVES

• Demonstrate enzyme activity by the hydrolysis of starch by amylase.

• Determine the effect of different temperatures on the rate of starch hydrolysis.

• Determine the effect of different pHs on starch hydrolysis.

• Demonstrate the presence of the enzyme catalase in living tissues

• Compare the relative amounts of catalase in different tissues.

• Demonstrate that oxygen is produced when hydrogen peroxide is decomposed by

catalase.

Answer these questions before you come to lab:

1. Define each of the following terms:

Catalyst

Activation energy

Enzyme

Substrate

Product

Denaturation

Hydrolysis

Metabolism

41

2. Why do living cells need enzymes?

_____________________________________________________________________

_____________________________________________________________________

INTRODUCTION

Enzymes are proteins folded into their tertiary structure which give them a particular 3-

dimensional shape. This highly specific folding creates a groove in the enzyme molecule, called

the active site. The active site has a very specific shape which only one substrate (with a

complementary shape) can bind. Any condition that causes the enzyme to unfold and lose its

shape will result in its inability to function.

An example of an enzyme is amylase, found in human saliva and also in germinating seeds. Its

substrate is the polysaccharide starch. Amylase catalyzes hydrolysis of starch to the disaccharide,

maltose.

H20 + amylase + starch → + amylase-starch complex→ maltose+ amylase.

In this lab we will investigate how two conditions, temperature and pH affect the ability of

amylase to hydrolyze (digest) starch.

Lugol’s iodine is used to detect starch which stains dark-blue/black in its presence. If starch is

digested by amylase to maltose, this color will disappear since maltose does not react in this way

with iodine. The color that remains will be that of iodine.

Exercise 1: Starch hydrolysis by the enzyme amylase

Procedure

42

1. Obtain a spot plate that has many small depressions on its surface.

2. Place a drop of iodine into each of the depressions. Each well will be used to detect

the presence of starch.

3. Obtain a test tube and fill it with 10 ml of starch. This is the reaction tube.

4. Add 1 ml of 1% amylase. Mix carefully by inversion, after covering the tubes with a

small piece of Parafilm®. Immediately remove 1 drop from the reaction tube and

place into one of the wells on the spot plate. A positive test for starch should be

observed.

5. Remove a small sample from the reaction tube and test for starch at 2 minute

intervals. Continue this for a 10-minute period, and record the time at which no

starch is detected (the time at which all the starch is converted to maltose).

6. Tabulate your observations making a note of the time interval and what you

observed.

Time (min) Starch present? ( + or - )

0

2

4

6

8

10

If starch is still present even after 10 minutes of reaction time, can you detect a lighter color

when you add the sample to the drop of iodine? If so, why?

_______________________________________________________________________________

_______________________________________________________________________________

Exercise2: Effect of Temperature on Starch Hydrolysis

What effect do you predict temperature will have on the reaction of amylase with starch?

_______________________________________________________________________________

43

_______________________________________________________________________________

At which temperature do you think the reaction will proceed best? Why? (Hint: Where is

amylase found?)

_______________________________________________________________________________

_______________________________________________________________________________

Procedure

1. Get 4 test tubes and label one each: ice; RT (room temperature); 40°C; boiling.

2. Into each tube, pipette 10 ml of starch solution, and place each tube in a water bath

of appropriate temperature. Incubate the tubes for 5 minutes to allow the starch to

come to that temperature (to equilibrate).

3. During the 5-minute incubation, prepare your spot plate by adding a drop of iodine

to each well.

4. After the 5-minute incubation, add 1 ml of the 1% amylase solution. Mix carefully

by inversion, after covering the tubes with a small piece of Parafilm®. Remove the

Parafilm® and return the tubes to the water baths. (Do not mix the tube in the boiling

water bath!)

5. At 2-minute intervals, remove 1 drop from each tube and test for the presence of

starch by dropping the solution into a well containing iodine.

6. Continue testing for the presence of starch at 2-minute intervals, as described above,

until no starch is detected, that is, until the hydrolysis is complete, in each of the 4

reaction tubes. Use the following table to keep track of the results for each test by

placing a + or - to indicate the presence or absence of starch.

Temp. (°C) 2 min. 4 min. 6 min. 10 min. 12 min. 14 min. 16 min. 18 min.

4 (ice)

25 (RT)

40 (warm)

100 (boiling)

7. From the above table, note the time needed for complete hydrolysis, and write the

44

times for each corresponding temperature in the table below.

Temp. (°C) Time to complete

hydrolysis (min.)

4 (ice)

25 (RT)

40 (warm)

100 (boiling)

45

Exercise 3: Effect of pH on Starch Hydrolysis

What effect do you predict pH will have on the hydrolysis of starch by amylase?

_______________________________________________________________________________

_______________________________________________________________________________

At what pH do you think the reaction will proceed best? (Hint: What is the pH where

amylase is found?)

_______________________________________________________________________________

Procedure

1. Get 3 test tubes and label one each: pH 4, pH 7, and pH 10.

2. Pipette 5 ml of the appropriate pH buffer into each tube. Add 5 ml of the starch

solution to each tube, and mix by swirling.

3. Add 0.5 ml of the amylase solution to each tube; mix by inversion. Take 1drop

from each tube and test for the presence of starch, as described above.

4. Continue to test for starch every 2 minutes until the reaction is complete in each

tube, that is, until the iodine solution no longer changes color to dark-

blue/black. Use the following table to keep track of the results for each test by

placing a + or - to indicate the presence or absence of starch.

pH of Buffer 2 min. 4 min. 6 min. 10 min. 12 min. 14 min. 16 min. 18 min.

4

7

10

5. Note the time it takes for the hydrolysis to reach completion at each pH from the

table above and fill in the table below.

pH of Buffer Time to complete

hydrolysis (min.)

4

7

46

10

Were your results what you had predicted before starting the experiment? Why or why not?

_____________________________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________

Exercise 4: To demonstrate that different cell types produce varying amounts of the

enzyme CATALASE.

During cellular metabolism, cells produce a by-product, hydrogen peroxide (H2O2) which

is toxic to cells. To get rid of the hydrogen peroxide, cells produce an enzyme called catalase

which breaks down the harmful hydrogen peroxide into the harmless water and oxygen.

Hydrogen peroxide = water + oxygen

H2O2 = H2O + O2

When hydrogen peroxide is added to living cells, this reaction takes place and the oxygen

released can be observed as bubbles leaving the tissue.

In this experiment you will investigate the varying amounts of catalase in different cell types.

Procedure

1. Weigh out 1g of each of the tissues provided.

2. Cut up the tissues and place each of the chopped tissues into a test tube. Use a spatula

or a glass rod to push all of the tissue to the bottom of the test tube. You need to use

all identical test tubes for this experiment.

3. Place 1g of chopped potato into a test tube with about 10 ml of water and boil for

five minutes. Drain off the water.

What is the purpose of this test tube?

________________________________________________________________________

47

4. Add 5 ml of hydrogen peroxide to each tube and mark the level of the hydrogen

peroxide immediately. Do one tube at a time so that you can mark the level of the

hydrogen peroxide as soon as you add it.

5. Allow the tubes to stand for 5-7 minutes and then mark the height to which the foam

rises.

6. While you are waiting you can confirm that the gas being produced is oxygen by doing

the test for oxygen gas. Place a glowing splint into the test tube. Describe what happens.

________________________________________________________________________

7. Measure the height of the foam in mm and record your results in the table below.

Cell type Height of foam (mm)

Boiled potato

48

Review Questions

1. Consider the chemical reaction:

starch + water = maltose

a. Specifically what type of chemical compound is starch? maltose?

starch _____________________ maltose_____________________

b. What type of chemical reaction is represented by the equation above?

__________________________________________________________________

c. In this reaction what is the substrate? Product?

substrate _____________________ product _____________________

2. (a) At what temperature did the reaction proceed best? Why do you think this is

the ideal temperature for this enzyme?

____________________________________________________________________

____________________________________________________________________

(b) Explain why was there no breakdown of starch in the tubes placed at

(i) 100°C

____________________________________________________________________

____________________________________________________________________

49

(ii) 4°C?

____________________________________________________________________

____________________________________________________________________

3. (a) At what pH did this enzyme work best?

_______________________________________________________________________

(b) Amylase is an enzyme produced in the human body. State 2 areas of the human

body where amylase is found.

_______________________________________________________________________

_______________________________________________________________________

(c) Name an enzyme in the human body that works best at acid pH.

_______________________________________________________________________

4. What is the active site of an enzyme?

_______________________________________________________________________

_______________________________________________________________________

5. From your results, which tissue type produced the most

catalase?_________________________

Which produce the least? _____________________

Explain why there was no bubbling in the tube with the boiled potato.

_______________________________________________________________________

_______________________________________________________________________

In which organelle of the cell would you expect to find the enzyme catalase?

____________________________________________

50

51

EXERCISE 6

Osmosis and Diffusion

LEARNING OBJECTIVES

• Investigate the processes of diffusion and osmosis and understand their

importance to living cells.

• Determine experimentally how temperature and concentration affect the rate of diffusion.

• Determine experimentally the tonicity of unknown solutions;

• Demonstrate the role of selectively permeable membranes in diffusion.

Answer these questions before you come to lab:

1. Define the following terms:

Passive transport

Active transport

Selectively permeable

Osmosis

Simple diffusion

Equilibrium

2. If a solution outside of a cell contains a higher concentration of a solute (e.g.

glucose or sodium chloride) than the cytoplasm inside the cell, the solutions is

said to be ____________________. Water will ____________ the cell.

3. If a solution outside of a cell contains a lower concentration of a solute (e.g.

glucose or sodium chloride) than the cytoplasm inside the cell, the solution is said

to be __________________. Water will ____________ the cell.

4. If a solution outside of a cell contains the same concentration of a solute (e.g.

glucose or sodium chloride) than the cytoplasm inside the cell, the solution is said

to be _________________. Water will ___________________________ the cell.

52

INTRODUCTION

Water is an essential requirement of all cells. For example, a plant that is not

watered enough starts to wilt. In terms of osmosis and diffusion, there is not

enough water within the cells for them to retain their shape and strength, so the

plant starts to die. This is just one example of the importance of water and how

water movement is necessary for the maintenance of cell structure and function.

All cells have membranes that surround them. These membranes are said to be

selectively permeable, which means that the membrane allows molecules

through only if they are small enough to pass through the membrane.

This exercise demonstrates the process of osmosis in which water molecules

move from a high concentration of water to lower concentration of water and the

effect of temperature on this process.

Exercise 1: Effect if temperature on osmos is

Procedure

1. Prepare an artificial cell by taking a small piece of the pre-wetted dialysis

tubing and tying one end to make a tube. Dialysis tubing is a selectively

permeable membrane, much like that of the cell. It will allow small molecules

such as water through pores in its structure.

2. Place 5 ml of 60% molasses in the tube.

3. Carefully tie the other end of the tube to seal it.

4. Rinse the cell briefly under tap water to clean it and gently dry.

5. Use the electronic balance to weigh your cell (Cell 1). Record your results in

the table below to 3 decimal places. (Initial weight).

6. Repeat steps 1-5 to make another cell with 60% molasses (Cell 2).

7. Get two 600ml beakers. Half fill one of them with tap water, leave one on

your table and place Cell 1 in it.

8. Half fill the other beaker with water taken from the 40°C water bath. Place

this beaker into the water bath with Cell 2 in it.

Note the time you put the cells in the water and record the temperature of

the water in each case. You will leave them for 1 hour.

53

What do you think will happen to your cells? Will they shrink, swell or stay the

same? Explain your answer.

____________________________________________________________________

__________________________________________________________________

This is your hypothesis.

Table 1. After 1 hour, remove the cells and gently blot them dry with paper

towels and weigh them again. (Final weight).

Table 1.

Cell 1 (60% molasses)

(22°C room temp)

Cell 2 (60% molasses)

(40°C water bath)

Initial weight (g)

Final weight (g)

Weight change (g)

(Final-Initial weight)

What has happened to the weights of your cells?

________________________________________________________________________

Why do you think this has occurred?

________________________________________________________________________

To check whether your hypothesis was correct, compare your results with those of the

other lab groups.

Exercise 2: Effect of concentration on osmosis

What would be the result using different concentrations of molasses solution in the cells?

________________________________________________________________________

Check your hypothesis by making another cell.

1. Place 5ml of 80% molasses into the cell, rinse, pat dry and weigh. (Initial

weight).

2. Place the cell in a 600ml beaker half filled with tap water on your table.

54

3. After 1 hour remove the cell pat dry and weigh again. (Final weight).

Table 2.

Cell 1 (60% molasses) Cell 3 (80% molasses)

Initial weight (g)

Final weight (g)

Weight change (g)

(Final-Initial weight)

What is the difference in weight change between cell 1 and 3? ___________ g

If there were differences, what would account for those differences?

____________________________________________________________________

____________________________________________________________________

Why was it important to leave the cells in the water for exactly the same amount of time?

____________________________________________________________________

____________________________________________________________________

55

Exercise 3: Plant Cell Experiment

In this experiment you will investigate the effect of different concentrations of

sucrose solution on potato cells. The solutions are 0. 1M, 0.2M, 0.4M, 0.8M and

distilled water. (M means molar and is one way of expressing the concentration

of a solution. 1M is the molecular weight of sucrose in 1 liter of water. The concentration

increases from 0.IM to 0.8M). The solutions are labeled V, W, X, Y, and Z. We

will first weigh the potato tissue, place them in the solution for some time and then weigh

them again. From your results you should be able to identify each of the solutions

based what happens to your potato cylinders when they are left in the solutions.

The solutions may be hypotonic, hypertonic or isotonic compared to your potato

cells.

What would you expect to happen to the size of the cells (and hence the weight of

the cylinder) if the solution is

hypertonic

___________________________________________________________________

hypotonic

___________________________________________________________________

isotonic

_____________________________________________________________________

Procedure

1. Make a potato cylinder by pushing a cork borer all the way through the

potato. DO NOT PUT THE BORER THROUGH A SPOT THAT

ALREADY HAS A HOLE. Release the cylinder from the cork borer by

pushing a pencil or similar object through the hole in the borer.

2. Using a razor blade, cut both ends of the potato cylinder so that no potato peel

is present.

3. Make 4 more cylinders in the same way.

4. Use the electronic balance to weigh each cylinder (label them V-Z) and record

the weight in the table below. This is the initial (or starting) weight of the

cylinders.

Record your potato cylinder results here.

56

57

Table 3.

Cylinder in

(solution V)

Cylinder in

(solution W)

Cylinder in

(solution X)

Cylinder in

(solution Y)

Cylinder in

(solution Z)

Initial weight (g)

Final weight (g)

Final-initial

weight (g) + or -

5. Place each cylinder in a different test tube and pour in enough of each of

the solutions provided to ensure the cylinders are fully covered. Match the

cylinders with the solutions V, W, X, Y, and Z as shown in the table below.

6. Let the cylinder sit undisturbed for at least 90 minutes.

7. After 90 minutes, blot the potato cylinders GENTLY on a paper towel and

record the weights in the table above.

8. Calculate the weight change of your cylinders, indicating if the weight

increased (+) or decreased (-).

9. Now compare your results with the class results by writing the weight change

for each cylinder on the board.

10. Record the average of the class results in the table below.

Record the Class Results here.

Table 4.

V W X Y Z

Average weight

change (g) (+ or -)

Exercise 4: To demonstrate selective permeability.

A selectively permeable membrane will allow some molecules to pass through and not

others. This may be based on the size of the molecules. Dialysis tubing is a selectively

permeable membrane.

Glucose and starch are both carbohydrates. What type of carbohydrate is

Glucose? _______________________________

Starch? _________________________________

58

Procedure

1. Prepare an artificial cell as you did before in Exercise 1.

2. Fill the cell to about 5ml with the glucose /starch mixture.

3. Rinse the cell well and place in a beaker of distilled water and leave for 45

minutes.

4. After 45 minutes, get a clean test tube and measure out 2 ml of the water in

which the cell was sitting and place into the tube.

5. Add 2 ml of Benedict's solution.

Benedict’s solution is used to test for

____________________________________

6. Place the tube in the boiling water bath for about 5 minutes and observe

any color change.

7. Place a drop of iodine in a well of the depression plate. Add a drop of the water

taken from around the cell.

Iodine tests for ___________________________

8. Record your results in the table below.

Table 5.

Liquid from beaker tested

with

Color Substance present

Benedict’s solution

Iodine solution

Which substance was present in the water?

59

__________________________________

Which substance was not present in the water?

_______________________________

Explain why this substance was present while the other was absent from the water.

____________________________________________________________________

____________________________________________________________________

60

Exercise 5: Observing Plasmolysis.

Procedure

1. Take a leaf of Elodea and place it on a slide with a drop of water and put on

a cover slip.

2. Using the 40X objective, observe the cells under the microscope and draw 4

of the cells that you see.

3. Make a new slide with a fresh leaf but use a drop of solution A.

4. Draw 4 cells from this slide.

61

What difference do you observe between the cells in the 2 slides?

____________________________________________________________________

____________________________________________________________________

Describe what you observe happening in the cells in solution A.

____________________________________________________________________

____________________________________________________________________

____________________________________________________________________

What kind of solution is solution A compared to the cytoplasm of the cells? Explain

your answer.

____________________________________________________________________

____________________________________________________________________

62

Review Questions

1. Explain fully why all the cells placed in water gained weight.

____________________________________________________________________

____________________________________________________________________

____________________________________________________________________

2. Copy your results for cells 1 and 2 (Table 1) in the table below.

Cell 1 (60% molasses)

(22°C room temp)

Cell 2 (60% molasses)

(40°C water bath)

Initial weight (g)

Final weight (g)

Weight change (g)

(Final-Initial weight)

Explain why the cell placed in 40°C gained more weight in the time.

____________________________________________________________________

____________________________________________________________________

____________________________________________________________________

3. Copy your results for cells 1 and 3 (Table 2) in the table below.

Cell 1 (60% molasses) Cell 3 (80% molasses)

Initial weight (g)

Final weight (g)

Weight change (g)

(Final-Initial weight)

a. What is meant by the term 'concentration gradient'?

____________________________________________________________________

b. Explain why the cell with 80% molasses gained more weight in the

time.

____________________________________________________________________

63

4. In the table below, copy the weight change in your potato cylinders (Table 3).

Cylinder 1

(solution V)

Cylinder 2

(solution W)

Cylinder 3

(solution X)

Cylinder 4

(solution Y)

Cylinder 5

(solution Z)

Initial weight (g)

Final weight (g)

Final-initial

weight (g) (+ or -)

Keeping in mind that the solutions may be either, hypotonic, isotonic or hypertonic to

the potato cells, explain the weight change in each of your cylinders.

In which of the solutions did the potato cylinders gain weight?

____________________________________________________________________

Explain why they gained weight.

____________________________________________________________________

____________________________________________________________________

In which of the solutions did they lose weight?

____________________________________________________________________

Explain why they lost weight.

____________________________________________________________________

____________________________________________________________________

What would you say about a solution in which the cylinder neither gained nor lost

weight?

Explain your answer.

____________________________________________________________________

____________________________________________________________________

5. Record the results of the average weight change in potato cylinders placed in

the 5 different sucrose solutions, in the table below. (Class results Table 4).

64

The concentrations of the five solutions used were: 0.1M, 0.2M, 0.4M, 0.8M,

distilled water.

V W X Y Z

Average weight

change (g) (+ or -)

Which solution was water? Explain why you think so.

____________________________________________________________________

____________________________________________________________________

Which solution is 0.8M sucrose? Explain why you think so.

____________________________________________________________________

____________________________________________________________________

65

EXERCISE 7

Cellular Respiration

Learning objectives

• Observe the process of cellular respiration in yeasts

• Determine the effect of different variables on cellular respiration in yeast

• Illustrate how different organisms can affect the level of carbon dioxide in the

atmosphere

• Deduce that oxygen is used by germinating seeds

• Measure heat released as a by- product of cellular respiration

INTRODUCTION

Energy is required by all living organisms for metabolism. Where does that energy come from?

The process of cellular respiration involves the breakdown of complex organic molecules. By

breaking bonds in these molecules, energy is released in the form of adenosine triphosphate

(ATP). The ATP can be used to drive a number of cellular metabolic reactions in an organism.

The following chemical reaction illustrates the overall reaction that occurs in respiration.

C6H12O6 + 6O2 6CO2 + 6H2O + ATP + Heat

glucose oxygen carbon water

dioxide

The equation above summarizes the very complex process of cellular respiration which involves

a series of many biochemical reactions in a metabolic pathway. These reactions have been

organized into three stages: glycolysis, the Krebs Cycles (citric acid cycle), and the electron

transport chain. Some organisms can also generate ATP by the process of fermentation. The

processes of cellular respiration and fermentation are illustrated in the diagram below;

66

Answer the following questions before you come to lab:

1. What is the initial substrate for cellular respiration? ----------------------------

2. How may ATP molecules are produced during glycolysis? Krebs’ cycle? Electron

transport chain?

Glycolysis

Krebs’ cycle

Electron transport chain

Total

3. What is the final electron acceptor in aerobic respiration?

4. Why is heat released during cellular respiration when it cannot be used by cells?

5. If oxygen is not available this type of respiration is called

6. Name 2 molecules that are used as the final electron acceptor if oxygen is not

available. State the products formed in each case.

67

Final electron acceptors in

fermentation

Products

7. How may ATP molecules are produced from fermentation? _________________

8. Name the three different molecules that make up a molecule of ATP.

In the following exercises, you will measure both examine and fermentation.

FERMENTATION

Exercise 1: Fermentation in Yeast

One type of anaerobic respiration most common to us involves the use of yeast in the production

of bread and alcoholic beverages e.g. beer and wine. The yeasts use sugar present in the extract

(e.g. grape juice) as a substrate and produce CO2 and alcohol as byproducts. This process is

known as fermentation. It is anaerobic since no oxygen is involved. We can measure the amount

of CO2 produced by the yeasts as an indication of how efficiently they are able to carry out

fermentation.

1. Obtain 4 fermentation tubes and fill them according to the table below. Your instructor

will demonstrate the proper way to fill the tubes so that no air bubbles are present in the

neck of the tubes.

Table 1 – Solution amounts of fermentation experiment.

Tube # 3M sodium

pyruvate

0.1 M NaF

(poison)

5% glucose water

1 2.5 ml 5.0 ml

2 5.0 ml 2.5 ml

3 5.0 ml 2.5 ml

4 7.5 ml

2. Finish filling the tubes with 25 ml of the yeast solution provided.

3. Incubate the tubes at 40°C for 45 minutes.

68

4. After 45 minutes, use a ruler to measure the height of the bubble (CO2) in each tube, and

write your results in Table 2.

Which tube would you expect to produce the most CO2? The least? Explain your answers.

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

Table 2 – Size of CO2 bubble.

Tube # Height of CO2

bubble (mm)

1

2

3

4

Exercise 2: Effect of Temperature on Fermentation

1. Obtain 2 more fermentation tubes (tubes 5 and 6).

2. Prepare them exactly as Tube 1. Place 2.5 ml glucose and 5.0 ml water into each tube,

and fill with yeast solution.

Put tube 5 at room temperature (20°C) and tube 6 in the refrigerator (4°C)

Tube 1 (40°C) from the previous exercise is included in this experiment

3. Measure the size of the bubble after 40 minutes and record your results in Table 3.

69

Table 3 – Size of CO2 bubble.

Tube # Temperature Height of CO2

bubble (mm)

1

5

6

Which tube would you expect to produce the most CO2? The least? Explain your answers.

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

Exercise 3: Release of carbon dioxide during anaerobic respiration

In this experiment you are going to use a yeast mixture. The yeast mixture was prepared by first

boiling a sugar solution (to remove all dissolved air) and then adding the yeast after it was

cooled.

Procedure

1. Use the apparatus provided to setup the experiment as shown in the diagram below.

2. Half fill the large test tube with the yeast mixture.

3. Pour in oil just to cover the surface of the mixture.

70

What is the purpose of the oil layer?

________________________________________________________________________

4. Half fill the other tube with phenol red.

What is the reason for using phenol red?

________________________________________________________________________

5. Place the stopper with the delivery tube tightly (BE CRAEFUL!) on the tube with the

yeast.

6. Arrange both tubes on the test tube rack so that the end of the delivery tube is submerged

in the phenol red.

7. Set up an identical experiment but use killed yeast instead.

What is the purpose of this duplicate experiment? _______________________________

Why was oil added to the surface of the yeast?

________________________________________________________________________

________________________________________________________________________

71

What is the color of phenol red in a neutral solution?

________________________________________________________________________

________________________________________________________________________

Explain why the color changed.

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

Exercise 4: How organisms affect the amount of carbon dioxide in the atmosphere.

Procedure

1. Label four large test tubes 1-4.

2. Place 5 ml phenol red into each tube.

3. Place the following into the tubes and stopper tightly (see diagram).

Tube Organism(s)

1 a green leaf

2 some small animals in a piece of gauze

3 a green leaf and animals in a piece of gauze

4 no organisms

4. Place the tubes in a rack on the bench and observe periodically for about an hour.

5. Gently shake the tubes every 10 minutes and observe the time taken for any color change.

Record your results in the table below.

Time

(mins)

Color

Start Tube 1 Tube 2 Tube 3 Tube 4

10

20

30

40

50

60

72

Which tube changed first? Explain why this tube changed first.

__________________________________________________________________

__________________________________________________________________

What color change took place in tube 1? Explain.

__________________________________________________________________

__________________________________________________________________

Describe what was happening in tube 3.

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

73

Exercise 5: Use of oxygen during respiration by germinating seeds.

Soda lime is a chemical substance that absorbs carbon dioxide. Any carbon dioxide produced by

the organisms is removed by the soda lime.

Observe the experiment, which has been set up.

When the organisms use up oxygen, what will happen to the pressure in the flask?

________________________________________________________________________

Describe what you observe taking place in each of the glass tubing.

________________________________________________________________________

________________________________________________________________________

What is the function of the potassium hydroxide (soda lime) pellets?

________________________________________________________________________

Explain why the level of the colored water rose in one glass tubing and not in the other.

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

74

Exercise 6: Release of heat by germinating seeds.

The experiment was set up as follows:

1. Moist cotton wool was placed at the bottom of a thermos flask and the flask was filled

with germinating seeds.

2. A thermometer was inserted and the flask and cotton wool used as a stopper.

3. A second flask was set up in the same way with non-germinating seeds.

4. Note the temperature in each flask:

Flask with live seeds _______________________

Flask with dead seeds ______________________

Why were thermos flasks used?

________________________________________________________________________

Why was the flask with non-germinating seeds included in the experiment?

_______________________________________________________________________

Since respiration releases heat energy, what type of biochemical process is it?

___________________________________

75

Review Questions

Exercise 1: Anaerobic Respiration

Tube # Contents of Tube Height of CO2

bubble (mm)

1

2

3

4

1. What was the function of Tube 1 and Tube 4?

________________________________________________________________________

2. Although Tube 4 contained no glucose a bubble was still produced by the yeast. Where

did they get the sugar for respiration?

________________________________________________________________________

________________________________________________________________________

3. NaF is a poison. Which substances, essential for metabolic processes could be inhibited

by the NaF? Explain.

________________________________________________________________________

________________________________________________________________________

4. (a) Yeast carry out alcohol fermentation. How is alcohol fermentation different from

lactic acid fermentation?

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

76

(b) What effect did the addition of pyruvate have on the reaction in tube 3? Explain.

__________________________________________________________________

Exercise 2: Effect of temperature on respiration

Tube # Temperature Height of CO2

bubble (mm)

1

5

6

5. Which of the fermentation tubes (1, 5, or 6) produced the greatest amount of CO2?

Explain your results fully.

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

77

EXERCISE 8

Photosynthesis

LEARNING OBJECTIVES:

• Understand the components of the equation for photosynthesis.

• Observe evidence of plants taking up carbon dioxide.

• Observe the relationship between the presence of pigments for

photosynthesis and the presence of carbohydrate product (starch).

• Observe evidence of plants producing oxygen.

• Demonstrate that light is necessary for photosynthesis.

• Observe the presence of stomata in the epidermis of plant leaves.

Answer these questions before you come to lab:

1. Define:

autotrophic_____________________________________________

Heterotrophic___________________________________________

2. During photosynthesis plants convert ___________ energy to _____________

energy in the form of ______________.

3. List the factors necessary for photosynthesis.

_______________________________________________________________

4. Which of these factor(s) are used in the light reactions?

_______________________________________________________________

5. Which are used in the light-independent reactions (Calvin cycle)?

_______________________________________________________________

6. What are the products of the light reactions?

____________________________________________________________

7. What are they used for in the Calvin cycle?

_____________________________________________________________

_______________________________________________________________

78

8. What are the products of the Calvin cycle?

_______________________________________________________________

9. Write the general equation for the process of photosynthesis.

_____________________________________________________________

EXERCISE 1: To show that carbon dioxide is taken up during

photosynthesis.

Introduction

Plants require CO2 to produce glucose during the light-independent reactions (also

called the ____________________) of photosynthesis. Therefore if CO2 disappears,

there is evidence that photosynthesis is occurring. A pH indicator solution can be

used to detect the uptake of CO2 by a plant. An indicator is a molecule that changes

color depending on pH. Today you will be using phenol red solution. Phenol red

solution turns yellow in acidic solutions (pH <7.0) and is red to neutral to basic

solutions (pH >7.0).

In order to see this color change take place, you will breathe CO2 from your lungs

into a solution of phenol red. The phenol red solution will begin basic (red) and

become acidic (yellow) as you add CO2. This is due to the following chemical

reaction between water and carbon dioxide.

H2O + CO2 H2CO3 water carbon carbonic

dioxide acid

If a plant is added to an acidic solution it can “fix” (or take up) the carbon dioxide.

Removing CO2 from the solution raises the pH (becomes more basic). This causes a

yellow solution to turn red.

Procedure

1. In a beaker, mix 50 ml of water with 10 drops of phenol red indicator.

2. Mark two test tubes with your initials. Fill one tube half-full with the phenol

red-water mixture. You will have phenol red-water mixture remaining in the

beaker.

79

3. Using a straw, gently blow into the beaker, being careful to avoid splashing.

Stop blowing as soon as your solution turns yellow. Otherwise, the experiment

will take longer because of the additional carbonic acid formed.

4. Fill the second labeled test tube half-full with this yellow solution (phenol red-

water rich in C02).

5. Add two pieces (about 3 cm each) of Elodea stem (with leaves) to each test

tube.

6. Pour off any excess phenol red-water solution so that the solution just covers

the Elodea.

7. Place both test tubes under the bright light for 30-60 minutes (this will

insure that the plant has adequate supplies of ATP and NADPH necessary

for the light-dependent reactions).

8. Observe the solutions every 10 minutes and record the time and color

changes you observe in Table 1.

Table 1. Record of time and solution color

Time Color

Has the color in either test tube changed? If so, why?

____________________________________________________________________

____________________________________________________________________

____________________________________________________________________

80

EXERCISE 2: To demonstrate that chlorophyll is required for

photosynthesis.

Explain what chlorophyll is used for during photosynthesis.

____________________________________________________________________

____________________________________________________________________

Procedure

A variegated leaf is one is which pigments are not evenly distributed.

1. Sketch this leaf in the "before" section of Figure 1, making sure to indicate

the location of the pigments (the parts that are white and those that are green)

Before After

Figure 1. Student sketch of leaf before and after staining

2. Bring half a beaker of water to boil.

3. Boil the leaf in water for 1 minute. This kills the leaf.

4. Carefully remove the leaf from the water.

81

5. Half fill a test tube with 95% ethanol, and place the killed leaf in it.

6. Place the test tube in the beaker of boiling water and boil for about or until all

of the pigment is removed.

7. Place the leaf into cool tap water for 30 seconds or until it becomes soft. The

alcohol make it hard)

8. Carefully spread the leaf out on a Petri dish and stain it with iodine. Wait 5

minutes and then make a sketch of the stained leaf in the ‘after’ section of

Figure 1. Indicate the areas that are black.

How is the presence of starch related to the process of photosynthesis?

____________________________________________________________________

____________________________________________________________________

____________________________________________________________________

Why would dark brown/black staining be absent if the portion of the leaf was

originally white?

____________________________________________________________________

____________________________________________________________________

____________________________________________________________________

Describe how carbon dioxide is used in photosynthesis.

____________________________________________________________________

____________________________________________________________________

____________________________________________________________________

____________________________________________________________________

82

EXERCISE 3. To show that light is necessary for photosynthesis.

Procedure

1. Obtain a leaf from a plant kept in the light and one kept in the dark.

2. Using two separate test tubes and the method described in Exercise 2, test

both leaves for starch.

What does boiling the leaf in water do? In alcohol?

____________________________________________________________________

____________________________________________________________________

____________________________________________________________________

Was there starch formation in the leaf from the plant kept in the dark? If so, was

this what you expected?

____________________________________________________________________

____________________________________________________________________

____________________________________________________________________

Why do plants store starch?

____________________________________________________________________

____________________________________________________________________

83

EXERCISE 4. To demonstrate that oxygen is produced during

photoysnthesis.

During the light-dependent reaction of photosynthesis, water is split to produce the

hydrogen needed for the reduction of carbon dioxide during the light-independent

reaction (or Calvin cycle). This splitting of water also produces oxygen, which is

released as a gas (O2), a by-product. The production of oxygen can be observed using

the aquatic plant, Elodea.

This demonstration has been set up so that molecules of oxygen produced during

photosynthesis are trapped in a test tube attached to the narrow end of a funnel.

Several fresh sprouts of aquatic plant are placed under the funnel and the entire

system is submerged in w a te r t a k in g c a r e to e n sur e t h a t the oxygen produced

will be trapped in the test tube rather than escaping into the air. Since tap water does

not contain much carbon dioxide, sodium bicarbonate is added to release carbon dioxide

into the water.

Observe the demonstration periodically during your lab period to observe formation

of oxygen as the level of water in the test tube is displaced. You may also see that

oxygen is being produced by observing the bubbles as they travel from the aquatic

plant to the test tube.

84

What would happen if this system was only allowed green light? Explain your answer.

____________________________________________________________________

____________________________________________________________________

Why is the system submerged in a solution of sodium bicarbonate rather than pure

water?

____________________________________________________________________

____________________________________________________________________

Exercise 5: Observing stomata on the epidermis of the leaf

Procedure

1. Paint a small area about the size of a dime with clear nail polish on the

underside of the leaf.

2. Allow the nail polish to dry completely.

3. Tape a piece of clear tape onto the dried nail polish.

4. Peel the nail polish (BE GENTLE!) by pulling on the tape.

5. Gently press the tape with your leaf impression onto a clean slide.

6. Examine under the microscope 40X.

7. Draw a few of the stomata you observe in the space below.

85

Lab Report

Exercise 1

1. What is phenol red?

____________________________________________________________________

2. What was the purpose of blowing into the water solution of phenol red?

____________________________________________________________________

3. What caused the color to change to yellow?

____________________________________________________________________

4. Explain why the color changed from yellow back to pink after leaving the

Elodea in it for an hour.

____________________________________________________________________

5. What was the purpose of the other tube (without the plant)?

____________________________________________________________________

____________________________________________________________________

Exercises 2 and 3

6. What does boiling the leaf in water do?

____________________________________________________________________

7. Why is the leaf then boiled in alcohol?

____________________________________________________________________

8. Which area of the variegated leaf contained chlorophyll?

____________________________________________________________________

86

9. What does a blue-black color with iodine indicate?

___________________________________________________________________

10. Which areas of the leaf stained blue-black?

____________________________________________________________________

11. Explain why only those areas stained blue-black?

____________________________________________________________________

____________________________________________________________________

12. Was there any starch in the leaf that had been left in the dark? Explain your

answer.

____________________________________________________________________

____________________________________________________________________

Exercise 4

13. Why was the plant submerged in a solution of sodium bicarbonate instead of

pure water?

____________________________________________________________________

14. What would have happened if green light were used instead? Explain your

answer.

____________________________________________________________________

____________________________________________________________________

____________________________________________________________________

87

EXERCISE 9

Cell Division LEARNING OBJECTIVES

• Describe the stages of interphase

• Model and draw the stages of mitosis and meiosis

• Compare and contrast mitosis and meiosis

• Identify the stages of mitosis in plant and animal cells

• Explain the importance of synapsis and crossing over

INTRODUCTION

Cell division is important to living organisms for reproduction, growth, repair of injured tissue,

and replacement of dead cells. Prokaryotic organisms, such as bacteria, have a single

chromosome and simply replicate that chromosome and split into two by the process of binary

fission. Eukaryotic organisms, on the other hand, have multiple paired chromosomes. Their cells

divide by a process known as the cell cycle, during which the nucleus divides. This division of

the nucleus is called mitosis when they divide asexually and meiosis when the cell division

produces gametes. Because they have multiple chromosomes, eukaryotic cells employ the use of

the spindle to organize the chromosomes and ensure that they are distributed correctly to the

daughter cells.

Answer the following questions before you come to lab:

The diagram below is of the cell cycle. Label each part of the cycle and describe (next to the

label) what happens during that stage.

88

In which stage of the cell cycle does the cell spend most of its time?_______________________

What is the spindle made of?______________________________________

What do the following terms mean?

Cytokinesis________________________________________________________________

Centromere________________________________________________________________

Chromatid_________________________________________________________________

Homologous chromosomes___________________________________________________

A duplicated chromosome is shown below. Label it.

Figure 2

Exercise 1: Mitosis/Meiosis Video

Pay close attention to the information in the video, since it will be followed by a video quiz.

Exercise 2: Modeling the stages of Mitosis

1. Use the playdoh to model two pairs of homologous chromosomes, each consisting of two

chromatids. Make one long pair (about 6 cm long) of one color e.g. blue and then make

its homologous pair of a different color e.g. red. Since they are homologous they must be

of the same length.

Also make one short pair (about 3 cm), also using different colors for each

homologue.

2. Model the stages of mitosis using the chromosomes you have made and record the stages

using colored pencils in the spaces provided on the next page.

89

Exercise 2: Modeling stages of Mitosis

Interphase

Prophase

Metaphase

Anaphase

Telophase/Cytokinesis

90

Exercise 3: Mitosis in animal cells (whitefish blastula) mitosis.

A blastula is the ball of cells produced as an embryo divides. After an egg (haploid) and sperm

(haploid) fuse during fertilization, the resulting cell is called the zygote (diploid). This cell

divides by mitosis and the resulting cells continue dividing repeatedly to produce the ball of cells

called the blastula.

In this exercise, you will examine slides of the whitefish blastula to observe the cell cycle of

animal cells.

1. Obtain a slide labeled “whitefish blastula.” Examine the slide under scanning power

(4X). You will note round circles. Each circle contains numerous sections of blastula.

Each blastula section has many cells, which maybe in various stages of mitosis or in

interphase.

2. Select a section and switch to low power and then high power for detailed observation.

(Follow the appropriate rules for using the microscope that you microscopy learned in

previously).

3. Work in groups and find the following stages of the animal cell’s life cycle. You may

refer to your text book and the diagram on the below.

Identify all the stages of the cell cycle in cells of the prepared slide of whitefish blastula and

draw them in the spaces provided on the next page.

• Interphase

• Prophase

• Metaphase

• Anaphase

• Telophase/cytokinesis

Figure 3 Mitosis in whitefish blastula

Exercise 3: Mitosis in animal cells (whitefish blastula) mitosis.

91

Interphase

Prophase

Metaphase

Anaphase

Telophase/Cytokinesis

Exercise 4: Mitosis in plant cells (onion root tip).

92

Mitotic divisions in plant cells take place only in specialized regions called meristems.

Meristems are present in the root tips and shoot tips of the plant and are regions of active growth

that result in the elongation of tips in stems and roots. There is also a meristem in the trunk of the

plant and mitotic division of cells in this region result in expansion of girth of plants. Cell

division continuously occurs in these meristem regions of plants; there are no comparable

regions in animals. In this exercise, you will examine prepared slides of the root tip meristem of

Allium (onion).

1. Obtain a prepared slide of a longitudinal section of Allium (onion) root tip.

2. Focus first with scanning power to get an overall view of the root tip (see diagram

below). Examine the region behind the root cap, which is the apical meristem of the root

tip.

3. Switch to high power and observe the stained chromosomes within the nuclei of

the cells in this region, and the cells undergoing mitosis (where no nucleus in present).

4. Work in groups and find the following stages of the animal cell’s life cycle. You may

refer to your text book and the diagram on the below.

Identify all the stages of the cell cycle in cells of the prepared slide of onion root tip and

draw them in the spaces provided on the next page. Also note any similarities and

differences between plant and animal cell mitosis.

Exercise 4: Mitosis in plant cells (onion root tip).

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Interphase

Prophase

Metaphase

Anaphase

Telophase/Cytokinesis

INTRODUCTION TO MEIOSIS

94

Answer these questions before you come to lab:

What do the following terms mean?

Tetrad__________________________________________________________________

Synapsis________________________________________________________________

Gonads _________________________________________________________________

Crossing over____________________________________________________________

Gamete_________________________________________________________________

How are the daughter cells produced from meiosis different from those produced from mitosis?

___________________________________________________________________________

___________________________________________________________________________

Meiosis is a form of cell division that occurs in the gonads, the ovaries and testes, of animals.

The purpose of meiosis is production of gametes which are haploid do that fertilization will

restore the diploid number of chromosomes. This process is called gametogenesis. Meiosis also

occurs in plants. In flowering plants this takes place in the anther and ovary of the flower.

Meiosis occurs in two cycles. Meiosis I consists of prophase I, metaphase I, anaphase I, and

telophase I, accompanied by cytokinesis. The second cycle consists of prophase II, metaphase II,

anaphase II, and telophase II, also accompanied by cytokinesis.

The chromosomes in diploid somatic (body) cells of eukaryotes exist in pairs called homologous

chromosomes. One chromosome of each pair comes from the father, and the other comes from

the mother. Homologous pairs contain similar, but not always identical, generic material for a

series of traits. They carry the same genes at specific loci, but they are often in alternate forms

called alleles. Somatic cells are diploid (2n), containing two sets of homologs in the same

nucleus. Following meiosis, all four daughter cells contain only one of each of the paired

homologs and are haploid (n).

Prophase I is unique in that homologous chromosomes pair with each other and intertwine as a

tetrad (see your textbook as a reference). This pairing of homologous chromosomes is called

synapsis. At this time, genetic material may be exchanged between non-sister chromatids during

a process called crossing over, in a form of genetic recombination. This process does not occur

during mitosis. Generally, each pair of homologues has at least one cross over.

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Exercise 5: Modeling the stages of meiosis

1. Use the playdoh to model two pairs of homologous chromosomes, each consisting of two

chromatids, as you did in Exercise 2.

2. Model the stages of meiosis using the chromosomes you have made. Simulate one cross

over event between the long pair and one cross over event between the short pair.

3. Record the stages using colored pencils in the spaces provided on the next page.

You may refer to the diagram on the following page.

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Figure 4. Meiosis

97

Exercise 5: Modeling the stages of meiosis 1

Interphase

Prophase 1

Metaphase 1

Anaphase 1

Telophase 1

Cytokinesis 1

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Exercise 5: Modeling the stages of meiosis II

Prophase II

Prophase II

Metaphase II

Metaphase II

Anaphase II

Anaphase II

Telophase II/Cytokinesis

Telophase II/Cytokinesis

99

EXERCISE 10

Genetics LEARNING OBJECTIVES

• Explain the genetic concepts of dominance and recessiveness.

• Efficiently use of the Punnett square

• Determine the outcome of monohybrid and dihybrid crosses.

• Calculate expected phenotypic and genotypic ratios given the genotype of two parents.

• Recognize that some human characteristics are inherited in a simple Mendelian fashion and others are not.

• Determine the outcome of genetic crosses involving the following principles: incomplete

dominance/co-dominance, multiple alleles, sex linkage

INTRODUCTION

Genetics is the science of heredity, which explains how characteristics are passed from parents to

their offspring. Much of our early understanding of genetics was due to the experiments of

Gregor Mendel done in the late 19th

century. Mendel was able to discover some of basic

generalizations of the laws of inheritance from experiments on pea plants. These principles can

be applied to may sexually reproducing organisms. However, genetics is a very complex science

and while some of these generalizations apply to the inheritance of some human characteristics,

many human characteristics are passed on using genetic mechanisms that were not evident to

Mendel. In this lab, we will look at Mendelian genetics and also some ways in which a few

human characteristics are inherited.

Before you come to lab, make sure you know the definitions of the following terms.

Homologous

chromosomes

Gene

Allele

Homozygous

Heterozygous

Dominant

100

Recessive

Genotype

Phenotype

Monohybrid

Dihybrid

Incomplete

dominance

Codominance

Multiple alleles

Sex linkage

The Punnett Square

In order to understand how alleles are passed on from parent to offspring, a Punnett square is

often used. A Punnett square shows the possible combination of alleles that can result when male

and female gametes are crossed. The first part of this lab will give you practice with both

monohybrid and dihybird crosses.

In order to complete a Punnett square, the alleles from one parent are listed on the top of the

Punnett square, and the alleles from the other parent are listed along the side.

It does not matter which parent is listed along the top, and which is listed along the side.

SIMPLE DOMINANCE

Monohybrid Crosses

Exercise 1

With simple dominance, alleles that completely mask the alternate form of the gene are said to

be dominant. In other words, dominant alleles are fully expressed whenever they are present.

Dominant individuals could have either an AA genotype (homozygous dominant) or an

Aa(heterozygous). The recessive allele “a” would be hidden whenever it was combined with

101

“A”. Thus, recessive phenotypes will only show up when individuals are homozygous recessive

(aa).

In onion sweet taste is dominant over bitter taste. Using the letter T, t, for taste, complete the

following crosses, and fill in the phenotype ratios of the offspring.

1. Homozygous Dominant X Homozygous Recessive

2. Heterozygous X Homozygous Recessive

3. Homozygous Recessive X Homozygous Recessive

4. Heterozygous X Heterozygous

Questions:

1. In which of the above crosses will all of the offspring express the dominant phenotype

and be heterozygous? ___________

2. In which of the above crosses will all of the offspring express the recessive phenotype

and be homozygous? ____________

Phenotype Ratio of Offspring

Phenotype Ratio of Offspring

Phenotype Ratio of Offspring

Phenotype Ratio of Offspring

102

3. In pea plants purple (P) is dominant to white (p). If you see a purple-flowered plant, what

are its possible genotypes? ________________________

4. Describe the experiment you would do to determine the correct genotype of the purple

plants.

Exercise 2

Note: The kernels on this ear of corn are either dark or light in color. Both parents of this

ear of corn only possessed dark-colored kernels.

1. What are the phenotypes of the kernels on your ear of corn?

Phenotype #1 ______________________

Phenotype #2 ______________________

2. Observe five rows of kernels. Record the number of each phenotype.

Phenotype #1 ______________________

Phenotype #2 ______________________

3. What is the approximate phenotypic ratio of this ear of corn? _____ : _____

4. Which allele is dominant? ____________________

5. Which allele is recessive? ____________________

6. What are the most probable genotypes and phenotypes of the parent kernels?

Phenotype Genotype

Parent #1 __________ __________

Parent #2 __________ __________

7. How many alleles influence this phenotype? __________

Exercise 3

103

Repeat the previous exercise using the new ears of corn that you are given.

1. Observe five rows of kernels. Record the number of each phenotype.

Phenotype #1 ______________________

Phenotype #2 ______________________

2. What is the approximate phenotypic ratio of this ear of corn? _____ : _____

3. What are the most probable genotypes and phenotypes of the parent kernels?

Phenotype Genotype

Parent #1 __________ __________

Parent #2 __________ __________

Exercise 4: Dihybrid cross

A dihybrid cross involves two characteristics located on different chromosomes. Recall

Mendel’s law of independent assortment which states that alleles of any pair of genes segregate

from each other independently of members of any other gene pair.

In guinea pigs, the allele for black coat color is dominant over the allele for brown and short hair

is dominant over long. If coat color is represented by B, b and hair length by H, h, the genotype

of a double heterozygous pig will the BbHh. Either of the pair of alleles B and b can end up in a

gamete with either of the pair H and h, so the possible combinations of theses alleles in the

gametes will be: BH, Bh, bH, and bh.

What is the genotype of the following guinea pigs:

True breeding black short-haired pig __________________________________________

True breeding brown long-haired pig _________________________________________

Heterozygous black pig with long hair ________________________________________

Heterozygous short-haired pig with brown fur __________________________________

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(a) A double heterozygous black short-haired pig was mated with a heterozygous black pig

with long hair.

Genotype of heterozygous

black short-haired pig

Possible Gametes

Genotype of Heterozygous

black pig with long hair

Possible Gametes

Use the Punnett square below to work out the genotypes of the offspring of the above cross.

(b) State the phenotypes of the offspring and give the ratio.

__________________________________________________________________

__________________________________________________________________

Exercise 5: Dihybrid cross (Corn)

105

Observe the kernels on this ear of corn carefully. Each kernel displays two different phenotypic

characteristics and there are four different phenotypic combinations.

1. What are the two phenotypic characteristics that the kernels display?

Phenotype 1 ____________________ and _____________________

Phenotype 2 ____________________ and _____________________

Phenotype 3 ____________________ and _____________________

Phenotype 4 ____________________ and _____________________

2. Observe five rows of kernels. Record the number of each phenotype. Record your

results on the board and pool the class results.

Phenotype 1 ____________________

Phenotype 2 ____________________

Phenotype 3 ____________________

Phenotype 4 ____________________

3. What is the approximate phenotypic ratio of this ear of corn? ____________________

4. Which alleles are dominant? _____________________ and ______________________

5. Which alleles are recessive? _____________________ and ______________________

6. What are the most probable genotypes and phenotypes of the parent kernels?

Genotype Phenotype

Parent 1 _____________/_____________ ________________________

Parent 2 _____________/_____________ ________________________

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Exercise 6: Human Genetics

Most human phenotypes like height, hair color, and stature are complex and influenced by

several genes. A few characteristics, however, are controlled by only a single pair of genes and

follow the rules of Mendelian inheritance. In this exercise, you will attempt to determine your

genotype for a number of these traits. If you demonstrate the dominant form of the gene, you

could be homozygous dominant or heterozygous for that trait. Determining your actual genotype

could involve developing family history or pedigree for that trait. Note that a phenotype that is

dominant will not necessarily be the most abundant one in a population.

1. Tongue Rolling: The ability to roll your tongue into a U-shape is dominant to the

inability to roll the tongue.

2. Widow’s Peak: A widow’s peak is a distinct V-shaped point in the frontal hairline. The

presence of a widow’s peak is dominant to a straight hairline.

3. Earlobe Attachment: Ear lobes may either be free hanging or attached to the side of the

head. To have free-hanging earlobes is dominant to having attached earlobes.

4. Hitchhiker’s Thumb: The ability to hyperextend or bend the end digit of the thumb

backward past a 45° angle. The presence of a hitchhiker’s thumb is recessive to the

inability to hyperextend the end of the thumb.

5. Mid-digital hair: The presence of hair (any amount) on the second (middle) digit of the

fingers is dominant to the absence of hair.

6. Freckles: The presence of freckles is dominant to their absence.

7. Dimples: The presence of dimples is dominant to their absence.

8. Thumb Overlap: When folding your hands together, to fold the left thumb over the right

is dominant to folding the right thumb over the left.

9. PTC Tasting: The ability to taste PTC (phenylthiocarbaminde) is dominant to the

inability to taste. Tasters will detect a bitter flavor.

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Trait

My Phenotype My Possible

Genotype

CLASS TOTALS

Tongue

Rolling

Roller

or

Nonroller

TT Tt

or

tt

Dominant:

Recessive:

2nd

finger shorter than

4th

Present

or

Absent

MM or Mm

or

mm

Dominant

Recessive

Widow’s

Peak

Peak Present

or

Straight

WW Ww

or

ww

Dominant:

Recessive:

Earlobe

Attachment

Free

or

Attached

FF Ff

or

ff

Dominant:

Recessive:

Hitchhiker’s

Thumb

(Last segment can be

bent back 60°)

Present

or

Absent

HH Hh

or

hh

Dominant:

Recessive:

Mid-digital

Hair

Present

or

Absent

HH Hh

or

hh

Dominant:

Recessive:

Freckles (face)

Present

or

Absent

FF Ff

or

ff

Dominant:

Recessive:

Dimples

Present

or

Absent

DD Dd

or

dd

Dominant:

Recessive:

Thumb

Overlap

Left

or

Right

TT Tt

or

tt

Dominant:

Recessive:

Right-handedness

Present

LL orLl

or

ll

Dominant

Recessive

PTC

Tasting

Taster

or

Nontaster

TT Tt

or

tt

Dominant:

Recessive:

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Exercise 7: Incomplete Dominance

In simple dominance that we have been investigating so far, the dominant allele is always

expressed when it is present where homozygous or heterozygous. In incomplete dominance,

there are two alleles for a trait, and neither one is truly dominant over the other. With incomplete

dominance, the phenotype of the heterozygote is unlike either of the homozygotes and expresses

an intermediate of both alleles a sort of blending of both phenotypes. A common example of this

is flower color in petunias. Petunias with red flowers have the genotype R1R

1. Petunias with

white flowers have a genotype R2R

2. A flower that is heterozygous (R

1R

2) is pink.

If a red-flowered plant is crossed with a white-flowered plant, what is the phenotype and

genotype ratios of the F1 offspring?

If two of the F1 generation were crossed, what would be the genotype and phenotype

ratios of the F2?

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Exercise 8: Co-dominance

In other cases, when neither allele is dominant, there is not really a blending to give an

intermediate phonotype but both alleles are fully expressed. This is known as co-dominance.

One of the best examples of co-dominance is demonstrated in the coat color of short-horned

cattle. Those individuals with reddish-grey (roan) coats are heterozygous R1R2, and are the

result from a mating between a red (R1R

1) shorthorn and a white (R

2R

2) shorthorn. Roan cattle

do not have roan-colored hairs. Instead, they have both red- and white-colored hairs mixed

together, which at a distance appears to be roan.

What if a roan short-horn cow is mated with a white bull. What will be the genotypic and

phenotypic ratios in the F1 generation?

List the parental genotypes of crosses that would produce at least some…

White offspring: _______________, _______________, _______________

Road offspring: _______________, _______________,

_______________, _______________

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Exercise 9: Sex Linked

The sex (gender) of humans and other primates is determined by a special pair of “sex

chromosomes,” the X and Y chromosomes. An individual with two X chromosomes if female,

while one X and one Y is male. The genes occurring on the sex chromosomes are called sex-

linked genes. Most sex-linked traits are X-linked. That is, they occur on the X chromosome.

The Y chromosome is much smaller than its homologue, the X chromosome. Consequently,

some genes present on the X are absent on the Y chromosome. This allows for sex-linked traits

to be more common in males. Males have only a single copy of the X chromosome. Having

only a single copy of the X chromosome allows for the alleles on that X chromosome to be fully

expressed. Females, with two X chromosomes, can be carriers (heterozygous) for a recessive

trait, but not exhibit the condition.

Color-blindness is a recessive X-linked human trait. If a color-blind man (XrY) fathers

children of a woman with the genotype XRX

R, what percentage of the sons would be

color-blind?

A man has a sex-linked form of pattern baldness. From which parent did he receive this

condition? Explain your answer.

a. mom b. dad c. no way to tell d. both

A girl is color-blind. From which parent did she receive this condition? Explain your

answer.

a. mom b. dad c. no way to tell d. both parents

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Exercise 10: Multiple Alleles and co-dominance

Many human traits are controlled by two alleles (i.e., the ability to roll the tongue (T) or the

inability to roll the tongue (t). Some characteristics are controlled by more than two versions of a

gene. These are called multiple alleles. The most well-known of these characteristics is blood

type in humans. The protein “I” on a red blood cell comes in two different forms, type A and

type B. The alleles that code for A and B proteins are co-dominant. Some individuals have cells

that lack this protein altogether. They have type O blood, which is a recessive condition. Thus,

from three alleles, IA, I

B, and i, we have a four possible phenotypes of blood: Type A, Type B,

Type O, and Type AB.

Phenotype Possible Genotype

Type A AA or AO

Type B BB or BO

Type O OO

Type AB AB

Is it possible for parents both with type AB blood to have a child that is type O? Why or why

not?

In a case of disputed paternity, a child is type O, the mother is type A. Could an individual of

the following blood types be the father?

AB _________________________

B _________________________

A _________________________

O _________________________

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Genetics Review Questions

You must indicate what the letter symbols you use mean and you must include the Punnett

square in all answers where appropriate.

1. In Labrador retrievers (a breed of dog) black coat color is dominant to brown.

(a) What would be the genotype of a heterozygous black dog?

(b) If a homozygous black dog is crossed with a brown dog, what will be the

phenotypic ratio of the offspring?

(c) If two black dogs from (b) above were crossed, what phenotypic ratio would

you expect in the offspring?

(d) If a heterozygous black dog is crossed with a brown dog, what phenotypic

ratio would result?

2. In humans normal skin pigmentation is dominant to albinism (lack of the pigment

melanin in the skin). Explain how two normal pigmented parents can produce an

albino child.

3. In pea plants round seed shape is dominant to wrinkled and yellow seed color is

dominant to green. Give the genotypes of the following:

(a) True breeding round yellow seed plants

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(b) Plants with green wrinkled seeds

(c) Plants whose seeds are wrinkled and which are heterozygous for yellow seed

color.

(d) Plants whose seeds are green and which are heterozygous for round seed color

(e) Suppose a plant with green wrinkled seeds is crossed a double heterozygous

plant with round yellow seeds.

(i) State the gametes a green wrinkled plant would produce.

(ii) State the genotype and gametes the double heterozygous would produce.

(iii)What phenotypes would this cross produce and in what ratios?

4. In cattle, red coat is incompletely dominant over white coat color. The intermediate

type is called roan, which is a mixture of red and white hair. Give the genotypes and

phenotypes (and their proportions) of a cross between two roan animals.

5. If a child is blood type O, and the mother is B, could an individual of the following

blood types be the father? Explain your answer.

(a) AB

(b) B

114

6. Red-green color blindness is a recessive X-linked trait. A woman with normal vision

whose father was color blind, married a color blind man.

(a) What are the phenotypes of their sons and daughters?

(b) Explain why the sons of a man with normal vision will not all necessarily

have normal vision.

115

EXERCISE 11

PROTIST, FUNGAL AND PLANT DIVERISTY

LEARNING OBJECTIVES

• Describe the diversity that exists among the protists.

• Identify the characteristics of fungi.

• Explain the alteration of generations in plants.

• Outline the divers features of plant structure and reproduction.

• Explain the features that allow land plants to successfully inhabit the terrestrial

environment

PROTISTA

This group includes a number of quite different organisms, which have been placed together

because a few basic similarities they share: they are all eukaryotic with more than one

chromosome and with a clearly defined nucleus and organelles, and divide by mitosis and

meiosis. Most are single celled but there are also many multi-cellular species. These organisms

have been placed together (for convenience?) in a group between prokaryotes and more complex

eukaryotes and in many cases there is no true genetic relationship between many of the species.

Hence the differences between them abound.

Differences between protists:

1. Method of feeding: autotrophs, predators, parasites and decomposers are all members of

this group.

2. Method of locomotion: Members utilize, flagella, cilia and pseudopods.

3. Size: Both microscopic and macroscopic species exist.

4. Cell wall: Some species have cell wall (made of cellulose) and others are wall-less.

5. Habitat: Habitats include fresh water, the marine environment and parasitic associations.

Exercise 1: Macroscopic protists

116

Observe the brown, red and green marine algae and make drawings of at least two types, to show

their body form.

Exercise 2: Microscopic protists

Use your microscope (x 40 objective) to make drawings of the following protists: Euglena,

Paramecium, Amoeba, and Spirogyra. Note the presence of the following structures wherever

they occur and label them on your drawing: cell wall, plasma membrane, nucleus, chloroplast,

pseudopod, cilia, food vacuole.

Euglena Paramecium

Amoeba Spirogyra

FUNGI

117

The fungi are spore-bearing, heterotrophic with absorptive nutrition, which reproduce both

sexually and asexually. Most of them are saprobes but many parasitic species also exist. The

group includes both microscopic types and macroscopic types. In terms of body form, most are

made up of thread-like filaments called hyphae. The mass of hyphae is called mycelium. Yeasts

are unicellular fungi (microscopic). They include species that are used in the making of bread

and alcoholic beverages as well as parasitic ones that cause yeast infections.

Exercise 3: Filamentous fungi

Use your microscope to draw portions of the slides of Rhizopus (the bread mold) and

Penicillium. Note the following structures and label them on your drawing; hyphae, spornagia,

spores.

Rhizopus

Penicillium

Exercise 4: Unicellular fungi: yeasts

118

Make drawings of some yeast cells from the slides provided.

Exercise 5: Macroscopic fungi

Observe the specimens of macroscopic fungi on display: mushrooms, puff balls, shelf fungi, etc.

PLANT DIVERSITY

119

Plants are photosynthetic organisms which all contain chlorophyll. Apart from those unifying

features, plants display a number of differences:

1. Some plants have a body plan in which roots, stems and leaves are present. Less

complex plant do not have this differentiation.

2. Some plants are vascular which means that they have transport tissues. Phloem

transports manufactured carbohydrate and xylem transports water. Other plants are

non-vascular.

3. Some plants need water for the fertilization of the female gamete by the male, others use

agents such as wind or insects to transport the male gamete.

4. Some plants produce seeds and others do not.

5. Some seed-bearing plants, produce flowers and fruit and so the seed development takes

place inside the fruit. Other seed-bearing plants produce naked seed.

6. Plants display a life cycle which alternates between two phases known as generations.

The gametophyte generation produce gametes and the sporophyte generation produces

spores. In some plants the gametophyte generation is dominant and in others the

sporophyte generation is dominant. Dominant means that this is the part of the life cycle

which is physically larger and the stage in which the plant spends most of its life.

Exercise 6: Bryophytes e.g. mosses

Make a drawing of the plant body of the moss. Label the following structures on your diagram:

rhizoid, stem-like structure, leaf-like structure, gametophyte, sporophyte, capsule.

Drawing of moss

120

Which generation is dominant? ____________________________________________________

Is the dominant haploid or diploid? _________________________________________________

What is the function of the rhizoids? ________________________________________________

Why are these plants found only in moist shady areas?

______________________________________________________________________________

______________________________________________________________________________

Exercise 7: Ferns

121

(a) Draw a part of the underside of a fern frond.

What are the brown structures called? _______________________________________________

(b) Use a needle and tease out one of the brown structures onto a microscope slide and

observe under the dissecting microscope.

What are these individual structures you teased out called? ________________________

What do they produce? ____________________________________________________

Which generation does the fern frond represent? Gametophyte or sporophyte?

________________________________________________________________________

122

Gently remove one of the fern prothalli (gametophyte) from the jar. Place it on a microscope

slide in a drop of water from the jar and cover with a cover slip. Observe using the low power of

your microscope and draw.

Which generation of the fern plant is this? ___________________________________________

Is it haploid or diploid? __________________________________________________________

Describe what happens on the prothallus (gametophyte).

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

123

Exercise 8: Gymnosperms e.g. pine

Make a drawing of a male and female pine cone.

What is the function of the male cone? ______________________________________________

What happens on the ‘leaves’ on the female cone?

______________________________________________________________________________

______________________________________________________________________________

Explain why these plants are called ‘gymnosperms’?

______________________________________________________________________________

______________________________________________________________________________

124

Exercise 8: Angiosperms: Flowering plants

(a) Make a drawing of the half flower and label all the parts. Give the function of each of

the parts you have labeled.

What part of the flower becomes the seed? _____________ The fruit? _____________

125

Exercise 9: Summary of Plant Characteristics

Indicate whether a plant group has a particular characteristic by putting a check mark in the

relevant column.

Characteristic Moss Fern Gymnosperm Angiosperm

Water needed for fertilization

Plant body has distinct roots,

stems, leaves

Rhizoids present

Sporophyte generation

dominant

Vascular

Seeds: naked

Seeds: enclosed

Flowers

Fruit

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EXERCISE 12

Animal Diversity

LEARNING OBJECTIVES

• Compare and contrast the body plan of different animal groups.

• Assign animals to their correct phylum based on their characteristics.

• Identify those characteristic that are important for successful terrestrial life.

INTRODUCTION

Animal bodies display a number of features that can be used in the identification of the different

animal groups.

Cephalization: a concentration of nerve and sensory cells in one area (anterior or head region).

This is the area of the animal that first encounters the stimuli in the environment.

Symmetry: Animals display radial or bilateral symmetry. In radial symmetry, the body

parts of the animal are arranged around a central point e.g. star fish. There are several axes that

can divide the body into mirror images of each other. Animals with bilateral symmetry have

only one axis that can produce mirror images. They are usually cephalized, with a definite head

region at the anterior of the body, a posterior region and dorsal (back) and ventral (underside or

belly) regions e.g. earthworms.

Segmentation: Many animal bodies are divided into interconnecting sections that are repeated

one after the other along the body. This is very obvious in earthworms.

Type of gut: The gut or digestive system may be incomplete or sac-like with only one opening

fo feeding and getting rid of waste. A complete or tubular gut, has two openings, a mouth at

one end and an anus at the other.

Coelom: A coelom is a cavity or space between the body wall and the digestive system. The

coelom protects and cushions the internal organs of the animal.

127

Exercise 1: Identify examples of different animal groups.

Fig. 1 is a chart which shows a simplified classification of the major animal groups. Use the

specimen display to locate examples of each of the groups listed on the chart. Write in at least

one example of each group.

Sponges

Cnidarians

Flatworms

Annelids

Mollusks

Roundworms

Echinodrems

Arthropods

Crustaceans

Arachnids

Insects

Myriapods

Fish

Amphibia

Reptiles

Birds

Mammals

Invertebrates

Vertebrates

All animals

Figure 1: Classification of Animals

128

Draw one animal belonging to each of the invertebrate groups.

Sponge

Cnidarian

Flatworm

Roundworm

Annelid

Mollusk

Arthropod

Echinoderm

129

INVERTEBRATES

Exercise 2: Characteristics of Invertebrates

Some of the characteristics listed in the Table 1 are visible when viewing an animal externally

and others are not. Observe the specimen display and check off the features characteristic of

each group. (Use your textbook to get information about features that can only be seen visible

internally).

130

Characteristic Sponges Cnidarians Flatworms Annelids Mollusks Roundworms Echinoderms Arthropods

Cells organized into

tissues

Organ systems

Coelom

Cephalization

Segmentation

Appendages

Symmetry: bilateral

Symmetry: radial

Type of gut: sac

Type of gut: tubular

Table 1: Characteristics of Invertebrates

131

VERTEBRATES

All vertebrates have the following features in common: a coelom, a circulatory system and an

internal skeleton. The skeleton consists of a backbone or vertebral column which encloses the

spinal cord and a skull or cranium which houses the brain. Apart from these unifying features,

vertebrate groups display some marked differences in their other characteristics.

Exercise 3: Characteristics of Vertebrates

Observe the vertebrate specimens on display and compare Table 2 with their characteristics (for

those features that are not visible externally, use your textbook to get the information).

Characteristic Fish Amphibia Reptiles Birds Mammals

Type of body covering

Breathing organs

Habitat

Type of appendages

Amniote egg?

Internal or external

fertilization?

Table 2: Characteristics of Vertebrates

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