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At the end of the lesson, tick of each of the learning intentions below that you have achieved, if you cannot

tick it off, revise over the section again. These are taken from the Science Syllabus.

1.1: Digestion and Enzymes • Identify and locate the major parts of the digestive system including the mouth, oesophagus,

stomach ,liver, pancreas, small intestine and large intestine, • Know their functions • Identify molars, premolars, canines and incisors, and describe their function • Enzymes: Investigate the action of amylase on starch; identify the substrate, product and

enzyme

1.2: Respiration and Breathing

Describe the functions of the main parts of a light microscope

Draw one example each of an animal cell and a plant cell, identifying the nucleus, cytoplasm and cell wall (plant cell), and indicating the position of the cell membrane

Explain how to prepare a slide from plant tissue and sketch the cells under magnification

Subject: Junior Certificate Science

Teacher: Mrs Welby

Week: Week 2

Lesson: Digestion and Enzymes, Respiration and Breathing System

1.0 Learning Intentions

2010 Report – Please use the below comments when looking at the relevant exam questions and see where some common

mistake were made.

Question Comment

Q1. H)

(Respiration)

(h) The names and/or formulas of the gases were given by most candidates. ‘Good air’ and ‘bad air’

was given by some candidates. Many candidates did not give the correct direction of movement of

gases while some candidates had O2 changing into CO2 in the alveoli.

Q2. A)

(Digestive)

(i) Some candidates appeared to confuse digestion with respiration, e.g. ‘produces/ releases energy’.

(ii) A number of candidates gave ‘to prevent choking’.

(iii) ‘Kidney’ appeared on some scripts for A/B.

(iv) This was well-answered

(v) This was generally not well answered. Some candidates appeared to confuse the large and small

intestines, and excretion with egestion.

Q1. F)

(Digestion)

Ordinary Level

f) This was generally answered well

Q3. B)

(Respiration)

Ordinary Level

(i) This was poorly answered. Many candidates gave ‘oesophagus’ or ‘spine’ or ‘throat’.

(ii) Few could give the correct function of the rings of cartilage. Many linked their answer to the

oesophagus which they named in part (i). A common mistake was to offer ‘to help oxygen (air) go

down’ or ‘to help you breathe.

(iii) This was poorly answered with most giving ‘lungs’ or ‘part B’. The term ‘alveoli’ was not well

known.

(iv) This part was well-answered.

2.0 Chief Examiners Comments

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3.1 Digestion and Enzymes

Digestion is the breakdown of food – our bodies need to convert food into smaller pieces so it can be absorbed through the intestines into the blood to be used around the body. Physical digestion is when the food is physically broken into smaller pieces (e.g. teeth chewing food) and chemical digestion is when the food is altered by chemicals or enzymes (e.g. Acid in the stomach or enzymes in saliva) Organs of the Digestive System

3.1.1 Functions of the Organs of the Digestive System

Organ Function

Mouth Food is physically broken down by the chewing action of the teeth and starch is chemically broken down by enzyme amylase in the saliva Amylase Starch Maltose

Oesophagus Muscular tube that food travels down to the stomach through

Stomach Muscular bag that holds food for hours. Physical digestion occurs here through churning and chemical digestion occurs through enzyme and acid action

Liver Large organ that produces bile, this travels to small intestine where it help to digest fats

Pancreas Produces enzymes that pass into the small intestine to help digest food

Small Intestine Food is further digested here and is then absorbed into the blood stream

Large Intestine Allows water to be reabsorbed from waste material leaving the body

3.0 Revision Notes

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3.1.2 Teeth Thea are 4 types of teeth in the adult jaw

3.1.3 Enzymes Definition: Biological catalysts that can speed up or slow down a reaction but they are not used up in the reaction.

• Play major role in digestive system • Involved in - growth of muscles

- Production of hair - Formation of blood cells - Breakdown of poisonous substances i.e drugs and alcohol

• Each enzyme carries out only one type of reaction i.e. it is specific to one reaction 3.1.4 Investigate the action of amylase on starch; identify the substrate, product and enzyme.

Procedure:

1. Add some saliva (which contains the amylase enzyme) to a starch solution, which is in a test tube.

2. Confirm beforehand that the substrate is starch by adding iodine to it – it should turn blue/black.

3. Heat in a water bath at 37 0C for 10 minutes.

4. The starch should now be converted to a simple sugar product called maltose so we need to test for this.

Add some Benedict’s solution and place in boiling water for a few minutes.

Result

The contents of the test-tube should turn red, indicating that sugar is present.

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3.2. Respiration and Breathing System Definition: Respiration is the release of energy from food. In every cell in our body respiration takes place, oxygen is required for this to happen, our lungs help up get oxygen into our body Formula: You must know the below formula for aerobic respiration

Glucose + Oxygen energy + carbon dioxide + water vapour

3.2.1 To demonstrate the products of aerobic respiration

1. Demonstrate that Carbon Dioxide is produced by Aerobic Respiration 1. Place a small volume of limewater in an airtight clear jar with a few woodlice on a wire gauze platform above the limewater - carbon dioxide turns limewater milky.. 2. Set up another jar but without woodlice. 3. Leave both jars at room temperature for many days. Results: the limewater went milky in the jar in the woodlice but remained clear in the jar without. Conclusion: the woodlice produced carbon dioxide.

2. Demonstrate that Water is Produced by Aerobic Respiration It is not possible to demonstrate this by the apparatus available in school. At best all that can be demonstrated is that exhaled air contains more water vapour than ordinary air (similar to the way it was shown that exhaled air contains more carbon dioxide then ordinary air). 1. Two clear jar are needed. 2. Each jar has a two hole stopper with plastic tubing through each hole. 3. Measure the mass of each jar with a top pan balance. 4. Place each jar in a container of crushed ice. 5. Draw ordinary air through one and pass breathed out air through the other again and again and again. 6. Note any changes in the jars and then measure the mass of each jar again. Results: condensed water is present in both jars but more in the one through which breather out air passed through and this jar also showed a greater increase in mass. (The liquid is water because it will turn dry white copper sulphate a blue colour.) Conclusion: we exhale much more water vapour than we inhale therefore we make water.

3. To Demonstrate that Heat is Produced by Aerobic Respiration 1. Set up a vacuum flask with live water-soaked germinating pea seeds. 2. Set up another flask with dead water-soaked pea seeds. 3. Measure the temperature each day with a thermometer each day. Results: the flask with dead seeds remained at room temperature (20° C), the flask with live seeds shows a major increase in temperature. Conclusion: respiration by living organisms produces heat

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3.2.2 Breathing System

Oxygen enters the body through the nose and the mouth, its travels down the trachea (held open by rings of

cartilage), its then enters the bronchus and then the bronchioles and finally into the alveoli. Here gaseous

exchange occurs and the oxygen enters the bloodstream and carbon dioxide enters the lungs and leaves the

body through exhalation. The oxygen is then carried by the blood to all of the cells of the body and this allows

respiration to occur and energy to be released.

Smoking can effect this process by stopping the cilia (small hairs in the lungs) from functioning to remove dirt

and bacteria, Bronchioles also get irritated and secrete lots of mucous – this gives you smokers cough.

3.2.3 Mandatory Experiment

Carry out qualitative tests to compare the carbon dioxide levels of inhaled and exhaled air.

Procedure

1. Suck air in through position A in Test tube A.

Result: it takes a long time for the limewater to go milky.

2. Replace the limewater and this time exhale air through the top of the tube as shown in Test tube B

Result: the limewater goes milky quickly.

Conclusion There is more carbon dioxide in exhaled air.

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Q1. Label the below diagram of the digestive system,

Q2. Name the 4 types of teeth _______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ Q3. Explain the differences between chemical and physical digestion ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ _______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ Q4. What are enzymes? ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ Q5. What is the equation for aerobic respiration? ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ Q6. Explain how oxygen travels from the nose to the blood stream ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

4.0 Homework Task

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5.0 Homework Correction

Q1. Explain each of the seven characteristics of life. The 7 characteristics of life refer to the characteristics that make define an organism as living, these are movement, respiration, response, feeding, excretion, reproduction and growth. If all of the characteristics are not present this means the organism is not living. Q2. Explain the three differences between plants and animals There are 3 main differences between plants and animals, movement, feeding and cell walls. Animals can move rapidly, plants move slowly. Animals cannot make their own food, they eat other animals and plants, plants can make their own food through photosynthesis. Q3. Draw a labelled animal cell and plant cell

Q5. Explain the parts of the microscope labelled 1-4 below

1. Eyepiece; The part of the microscope you look though 2. Objective Lens: Located on nosepiece, each has different magnification (x20, x40, and x100). 3. Stage: Where the sample is held and secured 4. Focus knob: Used to focus on sample, there is coarse focus and fine focus

Q6. Explain what makes up a balanced diet? A balanced diet is made up of the correct amounts of carbohydrates, proteins, fats, minerals, vitamins and water. Q7. Explain with the aid of a diagram, how you would test for the presence of a reducing sugar in a food.

1. Set up apparatus as shown in diagram 2. Add Benedict’s Solution to the food sample (coke, lucozade). 3. Heat the test tube in a 100°C water bath 4. Caution required with the flame of Bunsen burner, hot glassware

and the hot liquid in the beaker R Result - brick-red/orange colour,

Conclusion - reducing sugars are present

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