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Biology revision notes
There are two main ways which dissolved substances move into and out of cells.
Diffusion is when they move from a high concentration to a low concentration.
Active transport is from a low concentration to a high concentration. Against the
concentration gradient through a…

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The lining of the small intestine is folded into thousands of tiny projections known as
villi. These increase the uptake of digested food by diffusion. Only a certain number of
molecules can diffuse over a given surface areas of the gut lining at one time.
A good…

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Biology Revision notes

Also there are many air spaces inside the leaf allowing the carbon dioxide to come
into contact with lots of cells. This provides a large SA
Leaves lose water through evaporation. If Co2 could diffuse in and out freely, water
vapour would be lost very quickly.

Page 4

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The stomata will close which stops photosynthesis and risks overheating. The plant
will remain wilted until the temperature drops, the sun goes or it rains.

The transport system is absolutely vital to supply the needs of your body cells and to
remove the waste material they produce.…

Page 5

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The blood is a complex mixture of cells and liequid which carries a huge range
of substances around the body. The blood contains plasma, red blood cells,
white blood cells and platelets
The white blood cells are part of the immune system and are defence against

Page 6

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The muscles use a lot of energy. Muscles need a lot of energy, for example
the heart.
Your muscles also contain glycogen stores which can be converted to glucose
when needed.
Glucose + oxygen Carbon dioxide + water + energy
When you are resting your muscles use…

Page 7

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Kidneys also maintain the balance of water in your body. Too much water in
the blood would case the cells to have too much water in them, too little
water in the blood would meant that not enough water can move out the cell
and it becomes…

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Most people go to hospital for dialysis but in 1964 home dialysis machines
were made available so that patients didn't have to spend endless time in

Kidney transplants are where are where a kidney from another patient or body
and transplanted into the closest match. The…

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Another way to grow microorganisms is using a culture flask but for either
method warmth and oxygen is needed.
There's always a risk of mutation occurring when culturing bacteria, and a
dangerous pathogen could be made.
Contamination from external sources must be avoided and also health and…

Page 10

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Milk very rapidly goes off and tastes disgusting however milk can be changed
into food which can last for much longer. These changes depend on the use
of microorganisms
Yogurt is a staple part of the diet in the Middle East and has been for a very…


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