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B3 REVISION NOTES
Substances get in and out of cells through
3. Active transport
A cell may need to take up a substance against the concentration gradient. This involves
energy and is called `active transport'.
It is the only one of the tree methods that requires energy.
EXCHANGE OF GASES IN THE LUNGS
The lungs are in the thorax and protected by the rib cage.
The lungs exchange carbon dioxide and oxygen with the atmosphere.
They have a large surface area and are moist.
Diffusion takes place much more quickly through a wet surface.
EXCHANGE IN THE GUT
Digested food is absorbed by the capillaries alongside the small intestine (gut).
The small intestine has a `rich' blood supply.
The surface area of the small intestine is greatly increased by villi.
Absorption by the bloom is by diffusion and active transport.
EXCHANGE OF MATERIALS IN OTHER ORGANISMS
Fish exchange oxygen through their gills.
Frogs exchange oxygen through their skin.
Insects exchange oxygen through holes in their sides leading to a series of tubes.
EXCHANGE IN PLANTS
Plants exchange gases through their leaves.
Plants take up water and minerals through their roots.
Leaves and roots have adaptations for efficient exchange of materials.
Plants respire all the time
During daylight hours enough oxygen is produced by photosynthesis, so diffusion into the
leaves is mainly of carbon dioxide.
At night oxygen diffuses into the leaves, as respiration is the only process taking place.
Plants take up gases through stomata.
They take up water and can lose water through the stomata.
If plants lose too much water they wilt.
On hot days there is more energy causing the water to evaporate.
On dry days the air can hold more water.
On windy days any build up of humidity (water vapour) around the plant is blown away.
THE CIRCULATORY SYSTEM
The heart pumps blood around the body.
There are two separate circulation systems.
Arteries, veins and capillaries are the vessels involved in transporting blood.
TRANSPORT IN THE BLOOD
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Red blood cells transport oxygen.
Blood plasma transports carbon dioxide, urea and the products of digestion.
THE EFFECT OF EXXCERCISE ON THE BODY
During exercise muscles need more energy.
More glucose and oxygen need to be transported to the muscles.
To do this there are changed in heart rate, in breathing and in blood supple to the actively
respiring muscle cells.
Muscles can become fatigued after a long period of activity. They may be respiring
anareobically as they cannot get enough oxygen.…read more
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Microorganisms can be grown on a large scale in industrial fermenters.
The conditions in a fermenter must be very carefully controlled.
A mycoprotein can be produced using the fungus Fusarium.
They are produced in Fermenters.
The mould penicillin produces the antibiotic.
Biogas is mainly methane.
It is made up by the anaerobic fermentation of a wide range of waste substances and plant
material containing carbohydrate.
Biogas can be made on a large and a small scale.…read more