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Biology Unit 2 – Biology Unit 2 – The Components of The Components of

LifeLife

EdExcel Additional ScienceEdExcel Additional Science

19/04/23Topic 1 – The Building Blocks of Topic 1 – The Building Blocks of CellsCells

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4)1)

5)

3)

A Typical Animal CellA Typical Animal Cell

Ribosomes – protein synthesis happens here

Mitochondria - energy is released here during respiration Cell

Membrane – controls what comes in and out

Cytoplasm - this is where the reactions happen and these are controlled by enzymes

2) Nucleus – controls the cell’s activities

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A Typical Plant Cell:A Typical Plant Cell:Cell wall – made of cellulose which strengthens the cell

Cell membrane – controls what comes in and out

Nucleus – controls what the cell does and stores information

Large vacuole – contains sap and helps support the cell Cytoplasm –

Chemical reactions happen here

Chloroplasts (containing chlorophyll) – this is needed for photosynthesis

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BacteriaBacteriaConsider a bacteria cell in more detail:

Bacteria – containing cytoplasm and a membrane surrounded by a cell wall. The genes are NOT in a distinct nucleus.

The cell contains a number of features, including:

1) Chromosomal DNA, containing the genetic info of the cell

2) Plasmid DNA, containing extra information such as defence mechanisms

3) Flagella, which helps the cell move

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Using a light microscopeUsing a light microscope

1. Eyepiece

3. Focus adjustor

2. Arm

4. Base5. Mirror

6. Stage

7. Lenses

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Magnification CalculationsMagnification Calculations

An old microscop

e!

A “stereo” microscope

These microscopes have different powers of magnification. Consider this image of velcro:

If the “loop” on this image is measured to be 20cm tall at a magnification of 100x how big is it really?

2mm

19/04/23Genes, Chromosomes and Genes, Chromosomes and DNADNA

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Some facts:

- DNA has a “double ______” structure

- This contains instructions on what a cell does, how the organism should work etc

- The instructions are in the form of a ______

- The code is made up from the four ____ that hold the strands together with hydrogen bonds

- The bases represent the order in which _____ acids are assembled to make specific ________

How genes How genes work - DNAwork - DNA

Words – helix, amino, code, bases, proteins

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Task: Find out how the structure of DNA was discovered, including:

1) An image of Crick and Watson with their original model

2) A brief desciption of what Crick and Watson did to discover DNA

3) How Franklin and Wilkins built on their work

DNADNA

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The Human Genome ProjectThe Human Genome ProjectIn 1990 an international project was launched called the “Human Genome Project”. The aim was to map the _______ makeup of the human race and includes work from ______ in 18 different countries.

Possible benefits:

• Improved genetic testing

• Improved predictions and screening of ________ diseases

• New gene ________ treatments

• New knowledge of how ______ have changed

Words – scientists, genetic, genes, inherited, therapy

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Uses of Genetic EngineeringUses of Genetic Engineering

With genetic engineering I can produce milk that contains:• Extra protein• Lower levels of cholesterol• Human antibodies

Basically, genetic engineering is when a gene is removed from one organism and inserted into another. Consider the example of making insulin:

19/04/23Genetic engineering - Genetic engineering - InsulinInsulin

Step 1: Using RESTRICTION ENZYMES “cut out” the part of the human chromosome that is responsible for producing insulin.

Step 2: Using another restriction enzyme cut open a ring of bacterial DNA (a “plasmid”). Other enzymes are then used to insert the piece of human DNA into the plasmid.

Step 3: Place the plasmid into a bacterium which will start to divide rapidly. As it divides it will replicate the plasmid and make millions of them, each with the instruction to produce insulin. Commercial quantities of insulin can then be produced.

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Cell growth 1 - MitosisCell growth 1 - Mitosis

Each daughter cell has the same number of chromosomes and

genetic information as the parent.

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Cell growth 2 - MeiosisCell growth 2 - Meiosis

Each daughter cell has half the number of

chromosomes of the parent.

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Mitosis vs. MeiosisMitosis vs. MeiosisMitosis:

1. Used for growth and repair of cells

2. Used in asexual reproduction

3. Cells with identical number of chromosomes and genetic information are produced (“clones”)

Meiosis:

1. Used to produce haploid gametes for sexual reproduction

2. Each daughter cell has half the number of chromosomes of the parent

During meiosis copies of the genetic information are made and then the cell divides twice to form four daughter cells.

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FertilisationFertilisation

The human egg and sperm cell (“GAMETES”) contain 23 chromosomes each and are created by meiosis.

When fertilisation happens the gametes fuse together to make a single cell called a ZYGOTE (“diploid”). The zygote has 46 chromosomes (23 pairs) and continues to grow through mitosis.

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Key wordsKey words

Gamete

Zygote

Diploid

Haploid

Gene

• Contains half the number of chromosomes

•This is formed when an egg is fertilised by a

sperm

• A section of DNA

• Contains the full number of chromosomes

•An egg or a sperm are called this

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Cloning AnimalsCloning AnimalsHere’s how Dolly the sheep was cloned:

Clone

Host mothers

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Pros and cons of cloningPros and cons of cloning

Cloning

Creating new food supplies

Risk of creating deformed animals or humans

Medicinal - Cloning new

organs for use when humans’

organs fail

Ethical issues – is it right to clone

animals or humans?

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Cell specialisationCell specialisation

White blood cell

Egg cell (ovum)

Ciliated epithelial cell

Nerve cell (neurone)

During the development of a multi-celled organism cells differentiate to form specialised cells:

A “stem cell” is a cell that hasn’t yet become specialised and can be found in embryos or bone marrow. These cells can be used to treat certain conditions but the use of these cells is very controversial.

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Stem cell researchStem cell researchStem cells are cells that have not yet specialised:

Egg and

sperm

Embryo

Cloned embryo

s

These stem cells have the potential to develop into any kind of cell. In grown adults they can be taken from bone marrow or they can come from embryos from unused IVF treatments. They can be used to treat conditions such as paralysis.The ethical issue:

Should these embryos be treated as humans?

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Making proteinsMaking proteins1) DNA “unravels” and a copy of one strand is made

2) The strand copy is made to produce mRNA

3) The copy (with its code) then moves towards the ribosome

4) The ribosome “decodes” the code which tells the ribosome how to make the specific amino acid

5) Amino acids are then joined together to form a polypeptide (protein)

19/04/23Mutating Mutating DNADNA

Each protein has its own specific number and order of amino acids. But what happens when DNA mutates?

This mutation will cause different amino acids (and therefore different proteins) to be formed. These mutations can be beneficial, harmful or neutral.

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Introduction to EnzymesIntroduction to EnzymesEnzymes are biological catalysts. They help the

reactions that occur in our bodies by controlling the rate of reaction.

An enzyme is basically a protein molecule made up of long chains of amino acids. These molecules are then “folded” to create a certain shape. Proteins are used in DNA replication, protein synthesis and digestion.

The enzyme’s shape helps another molecule “fit” into it (“lock and key”):

This shape can be destroyed (“denatured”) by high temperatures or the wrong pH:

Enzyme Substrate

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Enzymes are denatured

beyond 40OC

EnzymesEnzymesEnzymes work best in certain conditions:

Enzyme activity

Temp pH pH400C

Could be protease (found in the stomach)

Could be amylase (found in the intestine)

Enzymes are used in industry to bring about reactions at normal temperatures and pressures that would otherwise be expensive. However, most enzymes are denatured at high temperatures and can be costly to produce.

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Topic 2 – Organisms and EnergyTopic 2 – Organisms and Energy

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Respiration IntroductionRespiration IntroductionI enjoy taking samples using quadrats.

In order to do this, I need energy. Where does this energy come from?

Our energy comes from a process called respiration, which basically involves turning food and oxygen into energy and this reaction is controlled by enzymes.

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DiffusionDiffusionDiffusion is when something travels from an area of high concentration to an area of low concentration. For example, consider the scent from a hamburger…

The “scent particles” from this hamburger are in high

concentration here:

Eventually they will “diffuse” out into this

area of low concentration:

Oxygen passes into cells by diffusion

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Diffusion SummaryDiffusion SummaryDiffusion is when particles spread from an area of high concentration to an area of ___ concentration. The particles move along a “concentration _____” and this process takes no _____ (it’s a “passive” process”). Diffusion can be accelerated by increasing the _______ of the particles, which makes them move _______.

Words – faster, low, gradient, temperature, energy

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Diffusion in the lungsDiffusion in the lungsOxygen diffuses in and carbon dioxide diffuses out of blood in the lungs:

O2

CO2

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(Aerobic) Respiration(Aerobic) Respiration

Words – breathing, energy, grow, respiration, food, mitochondria

All living organisms have to move, _____, reproduce etc. Each of these life processes needs ENERGY. ___________ is the process our bodies use to produce this energy:

Glucose + oxygen water + carbon dioxide + ENERGY

The glucose we need comes from ______ and the oxygen from _________. Water and carbon dioxide are breathed out. The MAIN product of this equation is _________. Respiration happens in _________ in cells.

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Uses for this energyUses for this energyAnimals and plants have many uses for the energy they generate from respiration:

1) To build up sugars in ______

2) To build up body _______

3) To maintain a constant body ___________ (warm-blooded mammals only)

4) To build up sugars, ________ and other nutrients in plants

5) To build up amino acids and ________

Words – nitrates, tissue, proteins, respiration, plants

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The Effect of Exercise The Effect of Exercise Heart rate/min

Breathing

rate/min100

75

50

25

225

175

125

75

5 mins 10 mins 15 mins 20 mins

Rest Exercise Recovery

During exercise the following things happen: heart rate increases, breathing increases and arteries supplying muscles dilate. These three things all help muscles to get the oxygen and glucose they need.

19/04/23Cardiac Output and Heart Cardiac Output and Heart RateRate

The electrical impulses from the heart can be monitored using an electrocardiogram:

Using this information and the volume of blood pushed by the heart (the “stroke volume”) you can calculate the cardiac output of the heart:

Cardiac output = stroke volume x heart rate

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Muscles and exerciseMuscles and exerciseWhen we exercise our muscles are supplied with more oxygen and glucose, increasing the rate of respiration.

Muscles store glucose as glycogen which can then be converted back into glucose during exercise.

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Anaerobic respirationAnaerobic respirationUnlike aerobic respiration, anaerobic respiration is when energy is provided WITHOUT needing _________:

This happens when the body can’t provide oxygen quick enough for __________ respiration to take place.

Anaerobic respiration produces energy much _______ than aerobic respiration but only produces 1/20th as much.

Lactic acid is also produced, and this can build up in muscles causing ______ and “excess post-exercise oxygen consumption” (“EPOC”), which explains why breathing and heart rates remain high after exercise.

Words – debt, oxygen, fatigue, aerobic, quicker

Glucose lactic acid + a bit of energy

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PhotosynthesisPhotosynthesisBasically, photosynthesis is the process through which a plant makes its own food using carbon dioxide and water:

That’s a nice plant. I’m going to put it in the sun and give it lots of water

and air…

CO2

H2O

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Travels up from the roots

WATER

CARBON DIOXIDEEnters the leaf through small holes on the underneath

SUNLIGHTGives the plant energy CHLOROPHY

LL The green stuff where the chemical reactions happen

Photosynthesis – the 4 things you Photosynthesis – the 4 things you needneed

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Carbon dioxide + _____ glucose + _____

6CO2 + 6H20 C6H12O6 + 6O2

Sunlight

Chlorophyll

Sunlight

Chlorophyll

The GLUCOSE produced by photosynthesis is used by the plant for _______ (through ____________). It is stored in the plant as ___________.

Words – respiration, starch, water, oxygen, energy

Photosynthesis equationsPhotosynthesis equations

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Large surface

area

Thin structure

Network of veins

Lots of chlorophyll

Structure of the LeafStructure of the Leaf

Transparent

Packed with

chloroplasts

Lots of air spaces

Holes

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Limiting PhotosynthesisLimiting Photosynthesis

1. Temperature – the best temperature is about 300C – anything above 400C will slow photosynthesis right down

2. CO2 – if there is more carbon dioxide photosynthesis will happen quicker

3. Light – if there is more light photosynthesis happens faster

What factors could limit the rate of photosynthesis?

19/04/23Drawing graphs of these Drawing graphs of these factorsfactors

1. Temperature

Photosynthesis is controlled by enzymes – these are destroyed at temperatures above 400C

2. Carbon dioxide

3. Light

Photosynthesis increases at first but is then limited by a lack of increase in temp or CO2

Photosynthesis increases at first but is then limited by a lack of increase in temp or light

19/04/23Encouraging Encouraging PhotosynthesisPhotosynthesis

Using knowledge of limiting factors, explain how plant growth is encouraged in a greenhouse:

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Water lossWater loss

Water loss through the stomata is biggest on a hot, dry, windy day. Plants that live in these conditions often have a thicker waxy layer.

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TranspirationTranspiration1) Water evaporates through the stomata

2) Water passes back into the leaf through xylem vessels by osmosis

3) Water is then pulled upwards through the xylem tissue

4) This is replaced by water entering from the root tissue

5) Water enters root hair cells by osmosis to eventually replace the water lost through respiration

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Xylem and PhloemXylem and Phloem

Xylem are used by the plant to transport water and soluble mineral salts from the roots to the stem and the leaves.

Phloem are tubes used by the plant to transport dissolved food to the whole plant for respiration and storage.

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Plant roots are made of “root hair cells” which have two features that help them to take in water and nutrients (“active uptake”):

Root hair cellsRoot hair cells

Root hair cells

Thin cell membrane

Large surface area

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More on Active TransportMore on Active TransportIn diffusion substances moved along a concentration gradient. In active transport, substances move against this gradient:

Outside cell

Inside cell

This process takes ______ and this comes from ___________. It enables cells to take in substances even though there are in very small __________. Root hair cells take in ______ using active transport.

Cell membrane

Words – concentration, energy, respiration, nutrients

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Carbon dioxide diffuses into the leaf through holes in the bottom surface.

Diffusion and Active Transport in Diffusion and Active Transport in plantsplants

More concentrated

Less concentrated

Mineral

…while plant nutrients are taken in by root hair cells using active transport.

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OsmosisOsmosisOsmosis is a “special kind of ___________”. It’s when water diffuses from a __________ area to a less concentrated area through a partially permeable _________ (i.e. one that allows water to move through but not anything else):

Water Sugar solutionIn this example the water molecules will move from left to right (along the concentration ______) and gradually _____ the sugar solution.

Words – membrane, concentrated, dilute, diffusion, gradient

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Strong sugar

solution

Medium sugar

solution

Weak sugar

solution

Pota

to c

ells

19/04/23Osmosis of water from Osmosis of water from leavesleaves

High conc. of water

Low conc. of water

Low conc. of water

Water leaves the plant by diffusing through osmosis into the air spaces and then evaporating.

19/04/23Taking samples of an Taking samples of an ecosystemecosystem

Using different “sampling techniques” we can measure changes in an ecosystem. The two main measurements are:

1)The physical conditions of a habitat (temperature etc)

2)The populations of different species in that habitatSome common ways of measuring…

Measuring temp, pH

etc

Taking animal samples

Help!

Taking samples using

quadrats

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Topic 3 – Common SystemsTopic 3 – Common Systems

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FossilsFossilsFossils provide evidence of early life and could have been formed in many ways. Four examples:

This fossil of a bat was formed due to hard parts of the

animal not decaying

This bee and orchid pollen were

preserved in amber – the amber lacked

some of the conditions needed

for decay to happen

This fossil was formed by parts of its body being replaced by minerals

Fossilised footprints

Why could there be gaps in the fossil record?

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Fossil recordsFossil recordsFossil records can provide a useful way of observing a species’ development:

The problem is, many early forms of life only had soft bodies and the few remaining traces of them have been destroyed by geological activity. This makes it difficult for scientists to know what happened in the distant past.

The “Stenheim skull”, found in

Germany in 1933

Oh no…

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The Pentadactyl LimbThe Pentadactyl LimbThe “pentadactyl limb” refers to features like our hands that have five “digits”. It’s a common feature for mammals. How does that provide evidence for evolution?

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Plant GrowthPlant GrowthPlants grow due to their cells dividing through mitosis and each cell growing through elongation. The cells then specialise into root hair cells, palisade cells etc. Unlike animals, plants continue to grow for the rest of their lives.

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Human GrowthHuman GrowthIn humans, we grow by cell division through mitosis and cell cells becoming specialised. There are five main areas of human growth:1) Infancy (up to two years)

2) Childhood (2-11)

3) Puberty (11-13/15)

4) Adulthood (15 upwards)

5) Old age (60+ years)

Growth rate (cm/year)

Age

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The four parts of bloodThe four parts of blood1. RED BLOOD CELLS – contain haemoglobin and carry ______ around the body. They have no _______ and a large surface area.2. PLATELETS – small bits of cells that lie around waiting for a cut to happen so that they can ____ (for a scab).

3. WHITE BLOOD CELLS – kill invading _______ by producing _________ or engulfing (“eating”) the microbe.

These three are all carried around by the PLASMA (a straw-coloured liquid). Plasma transports CO2 and ______ as well as taking away waste products to the ______.

Words – antibodies, clot, kidneys, oxygen, nucleus, glucose, microbes.

19/04/23Cells, tissues, organs and Cells, tissues, organs and systemssystems

Basically, all living things are made up of cells…

A group of CELLS makes up a TISSUE

A group of TISSUES makes up an ORGAN

A group of ORGANS makes up a SYSTEM

A group of SYSTEMS make up an ORGANISM

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Another exampleAnother exampleHere’s another example in humans:

Muscle cells

Muscle tissue

Organ

System

Organism

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The Circulatory systemThe Circulatory systemThe circulatory system is responsible for pumping ______ around the body. We need blood to be taken around the body because blood contains ________ and _______. These are needed so that all the ____ in our bodies can produce _____ through _________.

The main organs in the circulatory system are the _____, the lungs and the kidneys.

Words – energy, heart, blood, glucose, respiration, oxygen, cells

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The HeartThe Heart1. Deoxygenated blood (i.e. blood without oxygen) enters through the vena cava into the right atrium

2. It’s then pumped through the tricuspid valve into the right ventricle

3. It’s then pumped through the semi-lunar valve up to the lungs through the pulmonary artery

4. Oxygenated blood from the lungs enters through the pulmonary vein into the left atrium

5. It’s then pumped through the bicuspid valve into the left ventricle

6. It’s then pumped out of the aorta to the rest of the body

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““Double Circulation”Double Circulation”1) Blood gets pumped from the heart to the lungs and picks up oxygen. The haemoglobin in the cells becomes oxyhaemoglobin

2) The blood is then taken back to the heart…

3) The heart pumps the blood to the intestine (where oxygen and glucose are removed). The oxyhaemoglobin is split up into oxygen and haemoglobin…

4) … and to the rest of the body (where oxygen is also removed)

5) After the oxygen and glucose have been removed for respiration the blood is sent back to the heart and starts again

19/04/23Arteries, veins and Arteries, veins and capillariescapillaries

Arteries carry high pressure blood away from the heart.

They have smaller lumen and no valves.

Veins carry low pressure blood back to the heart. They have thinner, less elastic walls

and have valves to prevent backflow of blood.

Capillaries have thin walls (one cell thick) to

allow glucose and oxygen to pass through.

Also used to connect arteries to veins.

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The Digestive SystemThe Digestive SystemMatch these functions with the parts of the digestive system that do them…

In here the food is chewed to start breaking it down. An enzyme (amylase) is also

added.

This tube uses muscle contractions to push the food

down

This organ mixes the food with

hydrochloric acid to kill bacteria

Enzymes are made here

Bile is produced here

Bile is stored here

Excess water is absorbed here

Food is absorbed into the bloodstream here

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PeristalsisPeristalsis

“Peristalsis” is the movement of muscles to push food down the

gullet.

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The digestive systemThe digestive systemThe whole point of digestion is to break down our food so that we can get the bits we need from it…

The main foods affected are CARBOHYDRATES – these are broken down into GLUCOSE.

Hydrochloric acid is produced in the stomach to kill bacteria. Digestion also depends on “enzymes”...

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Enzymes in digestionEnzymes in digestionEnzymes can be produced by the body to help _______. When they come into contact and react with food they break it down into ______ pieces which can then pass into the ______:

Carbohydrase (produced in the mouth, pancreas and small intestine) breaks _______ (a carbohydrate) down into glucose:

Protease (produced in the stomach, pancreas and small intestine) breaks _______ down into amino acids:

Lipase (produced in the pancreas and small intestine) breaks fats (_____) down into fatty acids and glycerol:

Words – blood, lipids, proteins, digestion, starch, smaller

Blo

od

stre

am

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Bile and The LiverBile and The LiverBile is a chemical produced in

the liver and stored in the gall bladder. It has 2 functions:

1) It neutralises stomach acid and produces alkaline conditions for enzymes to work in

2) It emulsifies (“breaks down” fats:

Fat globules

Fat droplets

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Diffusion in VilliDiffusion in VilliIn the intestine, large food molecules are broken down into smaller ones that then diffuse into the blood through villi in the intestine.

Villi also have a very good blood supply and a large surface area. They have tiny folds in their cell membrane called microvilli, which increase the surface area.

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Functional FoodsFunctional Foods“Functional foods” is a term that describes foods like:

Task: find out the claimed benefits of functional foods, including:

1) Probiotics

2) Prebiotics

3) Plant esters