AQA Biology B2

Hi guys. These are the biology notes I made for GCSE and basically all I revised from. Hope they help!

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  • Created by: Jessie
  • Created on: 17-06-10 13:56
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Nucleus: controls all cell activities, contains DNA for new cells
Mitochondria: energy from respiration released here
Cytoplasm: chemical reactions essential for life take place here
Cell membrane: controls passage of substances in and out of cells
Ribosomes: where protein synthesis takes place
A plant cell contains all of the components of an animal cell, plus three more unique to plant cells
Cell wall: made of cellulose, this strengthens and supports the cell
Vacuole: keeps the cell rigid to support plants, filled with cell sap
Chloroplasts: contain chlorophyll, found in the green parts of the plant, absorb light for photosynthesis
Here are some of the more common specialised cells:
FAT CELL used as storage cells, contain very little normal cytoplasm so there is more room for fat, can swell
to 1000 times their original size, have a few mitochondria because they have no need for energy

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CONE CELL in the light sensitive area of the eye (retina), make it possible to see in colour, contain many
mitochondria so we can continuously see in colour , have connections to optic nerves at bottom
SPERM CELL carry genetic information from male parent to egg, long tail has muscle like fibres to help it
swim, middle section packed with mitochondria to give it energy, large nucleus contains DNA
RED BLOOD CELL biconcave so carries more oxygen, can bend to fit through tight spaces, full…read more

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ROOT HAIR CELL increases surface area of root so it can absorb more minerals and water, has no
chloroplasts because it is underground
carbon dioxide + water > oxygen + glucose
Glucose can be used for : respiration, protein synthesis in ribosomes, conversion into fructose and sucrose or is
stored as starch
Photosynthesis can be limited by: light intensity, temperature or carbon dioxide levels
When the graph for a limiting factor levels off, it is no longer the limiting factor it has been replaced…read more

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Magnesium: needed to make clorophyll to absorb light for photosynthesis no photosynthesis means no glucose
plant only needs small amounts, but a deficiency will leave yellow patches on leaves where it can't produce
Iron: used for photosynthesis in plants, a deficiency means to plant can't photosynthesise, so it lacks energy and
has a stunted growth
Hydroponics is growing plants in water and adding the minerals needed for growth.…read more

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Detritivores start decay process they eat the dead animals or plants and produce waste.
Bacteria and fungi then digest everything they use some of the organic compounds for growth and reproduction,
but most is deposited. They also produce waste from respiration they need energy for digestion.
Ideal conditions = warm, moist, good supply of oxygen
Sewage treatment plants use microorganisms to break down bodily waste so it can be safely released into rivers.…read more

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When it evaporates, it cools the skin and takes heat from the body, though there is no evaporation if it is
too humid.
If the body gets too cold, the rate of reaction in cells decreases, so they can't make enough energy and die.…read more

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The catalysts aren't changed during the reaction, so can be used to catalyse many more reactions.
Examples of anabolic reactions include protein synthesis and converting glucose to glycogen this is called
assimilation.…read more

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Different factors can affect the enzyme performance these include pH, temperature, enzyme concentration and
substrate concentration.
At first, there is a relative increase as the pH increases, as it reaches the best pH for that enzyme's performance.
The enzyme's rate of reaction peaks when the enzyme reaches optimum pH, where the enzyme works best. Once
pH increases past this optimum level, the enzymes are denatured and can no longer catalyse reactions. Different
enzymes have different pHs, as shown on the picture above.…read more

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Enzyme concentration
As enzyme concentration increases, the rate of reaction increases, provided that there is excess substrate.
Substrate Concentration
As substrate concentration increases, the rate of reaction increases until all the active sites are occupied and the
rate consequently levels it is said to be saturated.…read more

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Enzymes are proteins which are made of long chains of amino acids folded into a specific shape. Extremes of
temperature and pH break the bonds holding the structure together. As the molecule unravels, the active site
loses its specific shape and the substrate no longer fits. The enzymes is said to be denatured.
Respiration happens in every cell in every living thing. It occurs in the mitochondria.…read more



The format came out wierd. But overall it was a great help. Much appreciated.

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