AQA Biology Module 2

Exam notes for B2 exam

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  • Created on: 09-01-11 14:37
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Animal Cells
Nucleus ­ controls the cells activities
Cytoplasm ­ where many chemical reactions take place
Cell membrane ­ controls the movement of materials in and out of the cell
Mitochondria ­ where energy is released during aerobic respiration
Ribosome's ­ where proteins are made (synthesised)
Plant Cells
Nucleus ­ controls the cells activities
Cytoplasm ­ where many chemical reactions take place
Cell membrane ­ controls the movement of materials in and out of the cell
Mitochondria ­ where energy is released during aerobic respiration
Ribosome's ­ where proteins are made (synthesised)
Cell wall ­ rigid for support
Chloroplasts ­ contain chlorophyll for photosynthesis
Permanent vacuole ­ contains cell sap
Not all plant cells have chloroplasts with chlorophyll
Specialised cells
When an egg is fertilised it begins to grow and develop.
At first there is a growing ball of cells.
Then as the organism gets bigger some of the cells change and become specialised.
There are many different specialised cells
Some cells in plants may become xylem or root hair cells
Some cells in animals will develop into nerve of sperm cells.
How do substances get in and out of cells? (Diffusion)

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Molecules move randomly because for the energy they have.
Diffusion is the random movement of molecules from an area of high concentration to an area of
lower concentration
The large the difference in concentration the faster the rate of diffusion the faster the rate of
diffusion.…read more

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Palisade layer ­ palisade cells at top of leaf so they are closer to light, tightly packed together and
full of chloroplasts
Spongy layer ­ cells not tightly packed together have a larger surface area available for gas
exchange and some chloroplasts.
Lower epidermis ­ guard cells open and close the stomata to control water loss
Stomata allows gases to move in and out of the leaf
Limiting factors
Light, temperature and amount of carbon dioxide can limit the rate of photosynthesis.…read more

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It is more accurate than a pyramid of numbers as it represents the mass of the product rather than
the amount.
You can draw pyramids of biomass to scale to give a more accurate picture.
Energy losses
Not all of the food eaten can be digester, so energy is lost in faeces (waste materials)
Some of the energy is used for respiration, which releases energy for living processes.…read more

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The carbon cycle
Photosynthesis removes co2 from the atmosphere.
Green plants as well as animals respire. This returns co2 to the atmosphere.
Animals eat green plants and build the carbon into their bodies.
When plants or animals die (or produce waste) microorganisms release co2 back into the
atmosphere through respiration.
A stable community recycles all of the nutrients it takes up.
Enzyme structure
Enzymes are biological catalysts ­ they speed up reactions.
Enzymes are large proteins and each has a particular shape.…read more

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Aerobic respiration is the release of energy from food when oxygen is available.
The process takes part mostly in the mitochondria.
The energy released is used to ­
Build larger molecules from smaller ones
Enable muscle contraction in animals
Maintain a constant body temperature in mammals and birds.
Build sugars nitrates and other nutrients in plants into amino acids and then proteins.
Enzymes in digestion
Digestion involves the breakdown of large, insoluble molecules into smaller soluble molecules.…read more

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Isomerases to convert glucose into fructose to reduce amount of fat in sweet foods as less is
needed.
Controlling internal conditions (Homeostatis)
The processes in your body that help to maintain constant internal environment are known as
homeostatis.
We must remove waste products produced through chemical reactions from the body.
Carbon dioxide is a waste product of respiration it is excreted through the lungs
Some of the amino acids we take in are not used.…read more

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The pancreas monitors and controls the level of sugar in our blood.
I f there is too much sugar in our blood the pancreas produces the hormone insulin that results in the
excess sugar being stored in the liver as glycogen.
If insulin is not produced the blood sugar level may become fatally high.
If the pancreas is not producing enough insulin, this is known as diabetes.
It can sometimes be controlled by diet of the person may need insulin injections.…read more

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Each gamete has only one chromosome from the original pair.
All of the other cells are different from each other and the parent cell.
Sexual reproductions results in variation as the sex cells (gametes) from each parent fuse, So half the
genetic information comes from the father and half from the mother.
From Mendel to DNA
Gregor Mendel was a monk who worked out how characteristics were inherited.
His ideas were not accepted for many years.…read more

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