Complete Biology Revision (incomplete-working progress)

I have been putting these notes together recently and they are not finished yet, but I figured that with the GCSE exams so near i may as well put up what i have got... please comment but dont state the obvious that they are incomplete:D... thats just plain silly:P

P.S i made them nice and colourful (yes i actually spent my time changing font colours ...but it does help if you are a visual learner and also doesnt look as daunting when it comes to revising)

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What are enzymes?
Enzymes are biological catalysts.

They speed up chemical reactions in all living things, and allow them to occur
more easily.

They occur in plant cells and animal cells.

Without them we would not be alive.

Enzymes are just chemical molecules, made up of proteins.

Each particular…

Page 2

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Optimum conditions
Each type of enzyme has its own specific optimum condition under which it works

Enzymes work best when they have a high enough substrate concentration for the
reaction they catalyse. If too little substrate is available the rate of the reaction is
slowed and cannot increase any…

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Protease and lipase enzymes are used in biological washing powders to remove
those stubborn stains.

Enzymes are also used in making foods and drinks. The enzyme pectinase helps
to break down the cells in fruit to release more of their juice.

Cell structure
Plants and animal cells share the…

Page 4

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Firstly they have a rigid cell wall made of fibres of cellulose (which we use to make
paper!) that gives them shape and strength. The cell wall fits closely just outside the
cell membrane like a plastic box with an inflated balloon stuffed inside.

Secondly they have a vacuole, which…

Page 5

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Diffusion: Molecules move from a place of high concentration into a place of low

Osmosis: a special kind of diffusion, which is very important in Biology it keeps us

Key Facts

1. Osmosis only involves water molecules nothing else. Osmosis is water
2. Osmosis occurs across a…

Page 6

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Oxygen from the air is able to diffuse into the leaves of plants through tiny airholes
called stomata. This is obvious in plants as they take in oxygen at nighttime and
give out the carbon dioxide produced by respiration.

Respiration and Photosynthesis
Photosynthesis formula:

Carbon Dioxide + Water + Energy…

Page 7

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The air that we breathe out has more carbon dioxide in it (4%) than we breathe in
(0.04%). It has less oxygen too, the air we breathe in has about 21% oxygen
whereas that which we breathe out has 16%.

The lungs
The air enters the lungs down the trachea…

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Again, like lactic acid, ethanol is poisonous that's why it affects brain cells! If there
is too much ethanol produced it will kill the cells. So it must be got rid of by using
oxygen in aerobic reactions.

Otherwise the plant cells get 'pickled' permanently!

Structure of Leaves


Page 9

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although just to be confusing, when there are more than one they are called

A stoma is just a hole. It is controlled by two guard cells which change shape to
either open or close the hole. Something makes water enter the cells by osmosis
and so they swell…

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Sun: If there is less sun, which usually means it is cooler too, then there is less
energy for photosynthesis and it occurs more slowly. So photosynthesis works best
when it is warm and sunny don't we all!

Photosynthesis and Transpiration
When plants have their stoma open during the day,…


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