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Biology 2Biology 2

AQA Additional ScienceAQA Additional Science

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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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4)1)

5)

3)

A Typical Animal CellA Typical Animal Cell

Ribosomes – protein synthesis happens here

Mitochondria - energy is released here

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

20/04/23More specialised animal More specialised animal cellscells

Red Blood Cell

Carries oxygen around the body

No nucleus and large surface area

I.D:

Function:

Features:

White blood cell

Egg cell (ovum)

Ciliated epithelial cell

Nerve cell (neurone)

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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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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

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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

20/04/23Leaf StructureLeaf Structure

Palisade

cells

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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

20/04/23Three factors can affect Three factors can affect photosynthesis: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

20/04/23Drawing 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

20/04/23What is the glucose used What is the glucose used for?for?

Glucose (sugar) can be used to make long chains of starch…

Glucose molecules

Starch molecule

This glucose is then used by the plant as a store of _____ and some of it may be used for _________. The energy released from respiration can be used to make ______ acids or to build up fats and _____ as a food store in a _____.

Words – seed, amino, glucose, respiration, oils

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2 common nutrients…2 common nutrients…

Nitrates: Used to make proteins Lack of it leads to stunted growth

Magnesium: Used to make chlorophyll Lack of it leads to yellow leaves

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Food chainsFood chainsA food chain shows where the energy goes in a food chain (in other words, “what gets eaten by what”):

Cabbage

Rabbit Stoat Fox

The arrows indicate where the energy is going

Plants convert the sun’s energy into

food

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Pyramids of biomassPyramids of biomassIn this food chain we can see that the mass of organisms in each stage is less than in the previous stage:

Cabbage

Rabbit Stoat Fox

We can draw a “Pyramid of Biomass” to show this pattern:

Mass of cabbages

Mass of rabbits

Mass of stoats

Mass of foxes

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Energy flow in a food chainEnergy flow in a food chainConsider the energy flow in this food chain:

Cabbage

Rabbit Stoat Fox

100% 10% 1% 0.1%

Clearly, not all of the ___’s energy that becomes stored in the _______ will end up in the fox. Only around ______ is passed on to the next stage in each food chain.

Energy is lost at each stage because of a number of reasons:

1) Each organism has to ____, keep warm etc

2) Energy is lost through faeces (______)Words – 10%, move, sun, waste, cabbage

20/04/23Sankey Diagrams for Sankey Diagrams for animalsanimals

Cold blooded animal Warm blooded animal

Faeces

Movement

Heat

FaecesMovemen

tHeat

20/04/23Improving the efficiency of a food Improving the efficiency of a food chainchain

Clearly, food chains aren’t very efficient. How could the efficiency of a food chain be improved?

1) Reduce the number of stages in the chain:

Cabbage

Rabbit Stoat

2) Limit an animal’s movement or keep it warm:

Fox

3) Use plant hormones to regulate the ripening of fruit

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Farming MethodsFarming MethodsThere are basically two types of farming method; “intensive” and “organic”:

Intensive Organic

Cost

Produce

Fertilisers/ food

Space

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Recycling ourselvesRecycling ourselves

Microbes are the key to this – they break down waste and dead bodies so that the products can be used by plants for growth. Microbes work best in warm, moist conditions where there is plenty of oxygen.

Eating

Waste

Death

Broken

down

Absorption

20/04/23The Carbon The Carbon CycleCycle

CO2 in air 1. CO2 is taken

in by plants for photosynthesis and turned into carbohydrates

2. Plants release CO2 through respiration

3. The carbon taken in by plants is then eaten by animals

5. Animals (and plants) die and their remains are fed on by microbes and detritus feeders

6. These microbes also release CO2 through respiration

4. Animals release CO2 through respiration

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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:

The enzyme’s shape helps another molecule “fit” into it:

This shape can be destroyed by high temperatures or the wrong pH:

Enzyme Substrate

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Enzyme use in natureEnzyme use in nature

Cells use glucose to generate energy – this process is called “respiration”. Respiration happens in mitochodria and is catalysed by enzymes.

Photosynthesis is catalysed by enzymes in the cells.

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(Aerobic) Respiration(Aerobic) Respiration

Words – breathing, energy, grow, respiration, food

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 _________.

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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 perform the life processes, such as moving, _____ etc

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, growing

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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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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)

20/04/23Industrial uses of Industrial uses of enzymesenzymes

1) Enzymes are used in washing powders to help digest fats and proteins in food stains. Biological washing powders will only work on 400C or lower.2) Enzymes are used in baby foods to “pre-digest” the proteins.

3) Enzymes are used to convert starch into sugar which can then be used in food.

4) Conversion of glucose into fructose – glucose and fructose are “isomers” (they have the same chemical formula), but fructose is sweeter.

20/04/23HomeostasisHomeostasisHomeostasis means “controlling internal conditions”:

Waste products that need to be removed + how

CO2

Urea

Internal conditions that need controlling + how

Temperature

Ion content

Water content

Blood glucose

Produced by respiration, removed via lungs

Produced by liver breaking down amino acids, removed by kidneys and transferred to bladder

Increased by shivering, lost by sweating

Increased by eating, lost by sweating + urine

Increased by drinking, lost by sweating + urine

Increased and decreased by hormones

20/04/23Controlling Body Controlling Body TemperatureTemperature

Wow it’s hot!

Also, temperature sensors in the skin detect the heat and send information to the brain.

The thermoregulatory centre in the brain detects “warm blood”.

When the brain detects the high temperature it takes two main steps....

20/04/23Maintaining Body Maintaining Body TemperatureTemperature

Cold Hot

Vasodilation

Vasoconstriction

20/04/23Controlling Blood Sugar Controlling Blood Sugar levelslevels

We need glucose in our bodies to help our cells to respire and produce energy. What happens if we have too much glucose?

If blood sugar is too high the pancreas releases

insulin

The liver then converts glucose into insoluble

glycogen and is removed from the blood

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DiabetesDiabetesDiabetes is a ________ in which a person’s blood sugar (i.e. glucose) level may rise to a _______ level. This is because the ______ doesn’t produce enough _________.

Diabetes can be treated by __________ carefully or by injecting extra insulin when needed. Diabetics have to test their blood sugar level before they decide how much insulin to _______ themselves with.

Words – insulin, disease, inject, dangerous, eating, pancreas

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Modern GeneticsModern Genetics

Guten tag! My name is Gregor Mendel. I am the father of modern

genetics because of the work I did on pea plants in 1865…

Take two plants; one which is pure-bred for tallness and one pure-bred for shortness, and cross them:

X

Mendel’s experiment:

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Modern GeneticsModern Genetics

All the plants produced were tall.

Now cross two of these plants…

3 out of every 4 plants were tall, leading Mendel to hypothesise that “for every characteristic there must be two determiners”

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Modern GeneticsModern Genetics

Achtung! Unfortunately, nobody knew about chromosomes or genes when I published my findings so no

one believed me until after my death, when more powerful

microscopes were available.

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MitosisMitosis

Each daughter cell has the same number of chromosomes and

genetic information as the parent.

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MeiosisMeiosis

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

Meiosis:

1. Used to produce gametes for sexual reproduction

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

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Sexual ReproductionSexual Reproduction

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. The zygote has 46 chromosomes (23 pairs) and continues to grow through mitosis.

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Boy or Girl?Boy or Girl?

X Y X

XX XYGirl Boy

“Allele”

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Father

Mother

Son

Daughter

Boy or Girl?Boy or Girl?

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Key wordsKey wordsGamete

Zygote

Allele

Dominant

Recessive

Homozygous

Heterozygous

•This allele determines the development of a characteristic

•This is formed when an egg is fertilised by a sperm

•This allele will determine a characteristic only if there are no dominant ones

•This word refers to a pair of chromosomes being made of two different alleles of a gene

•An egg or a sperm are called this

•This word refers to a pair of chromosomes being made of two of the same alleles of a gene

•An alternative form of a gene

20/04/23Genes, Chromosomes and Genes, Chromosomes and DNADNA

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Some facts:

- Made up of paired bases

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

- The instructions are in the form of a code

- The code is made up from the four bases that hold the strands together

- The bases represent the order in which amino acids are assembled to make proteins

- Everyone (apart from identical twins) has different DNA and people can be identified by “DNA finger

printing”

How genes workHow genes work

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Eye colourEye colour

In eye colour the brown eye allele is dominant, so we call it B, and the blue eye is recessive, so we call it b:

bbBB Bb

Homozygous brown-eyed

parent

Heterozygous brown-eyed

parent

Blue-eyed parent

What would the offspring have?

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Eye colourEye colourExample 1: A homozygous brown-eyed parent and a

blue-eyed parent:

Example 2: 2 heterozygous brown-

eyed parents

BB bbX Bb BbXParents:

Gametes:

Offspring: Bb Bb BbBb BB Bb bbbB

B B bb B bB b

(FOIL)

All offspring have brown eyes

25% chance of blue eyes

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Eye colourEye colourExample 3: A heterozygous brown-eyed father and a blue-eyed mother:

Bb

Bb Bb bbbb

bb

b bB b

Equal (50%) chance of being either brown eyed or blue eyed.

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B b

b

b

Another methodAnother methodExample 3: A heterozygous brown-eyed father and a blue-eyed mother:

B b

b Bb bb

b Bb bb

Father

Mother

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Example questionsExample questions

1) In mice, white fur is dominant. What type of offspring would you expect from a cross between a heterozygous individual and one with grey fur? Explain your answer with a genetic diagram.

2) A homozygous long-tailed cat is crossed with a homozygous short-tailed cat and produces a litter of 9 long-tailed kittens. Show the probable offspring which would be produced if two of these kittens were mated and describe the characteristics of the offspring (hint: work out the kitten’s genotype first).

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Inherited diseasesInherited diseases1) Cystic fibrosis – a disease that causes thick and sticky mucus to coat the lungs, gut and pancreas. It’s caused by recessive alleles:

2) Huntingdon's disease – a disease of the nervous system that causes shaking and eventually dementia. It’s caused by a dominant allele:

Embryos can be screened for alleles that cause these diseases before birth.

Ff FfX

Cc ccX

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Stem CellsStem CellsA while ago we considered examples of specialised cells:

White blood cell

Egg cell (ovum)

Ciliated epithelial cell

Nerve cell (neurone)

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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Research tasksResearch tasksTask

Present an argument concerning one of these two topics:

1) Use of stem cells from embryos in medical research

2) The use of embryo screening to identify deformities