Biology AQA Unit 3 Revision Summary

This is a revision summary that I created. Good luck with all exams :D

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  • Created on: 07-01-12 17:47
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Exchanging Materials:
Water and dissolved substances move:
Along a concentration gradient.
From high to low concentrations.
By osmosis and diffusion.
Active transport ­ the process of substances absorbed against a concentration gradient using energy from respiration.
Exchanging Materials in Plants:
Leaves have stomata to let carbon dioxide in and oxygen out (by diffusion). This leads to transpiration (loss of water
Exchanging Materials in Humans:
Human organ systems are specialised to help the exchange of materials, for example:
Villi in the small intestine absorb products of digestion by diffusion and active transport.
Alveoli in the lungs exchange oxygen and carbon dioxide (by diffusion).
Anaerobic Respiration:
Anaerobic respiration = Respiration that doesn't use oxygen. Occurs during vigorous exercise.
Produces lactic acid, which needs oxygen to be broken down ­ oxygen debt.
Glucose Energy + Lactic Acid
Aerobic Respiration:
Aerobic respiration = respiration that uses oxygen.

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Occurs during normal activity and produces more energy than anaerobic respiration (but less quickly).
Glucose + Oxygen Carbon dioxide + Water (+ energy)
The Circulation System:
Circulation system = heart, blood vessels and blood.
Oxygenated blood provides cells with food and oxygen.
Deoxygenated blood takes away waste products.
Blood travels away from the heart through arteries.
Blood returns to the heart through veins.
In the organs, blood flows through capillaries.…read more

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Released carbon
Alcohol ­ hops Alcohol ­ flavour Lactic acid clots milk
Result dioxide makes
added to flavour depends on grapes and thickens it
bread rise
Blood vessels take blood to kidneys Unwanted substances enter tubules Tubules join to form ureter
Unwanted substances reach bladder Unwanted substances released.
In a dialysis machine, blood flows between partially permeable membranes.
Kidney transplant replaces diseased kidney ­ rejection is a major problem, so...
A donor kidney with a close tissue type is used (close relative).…read more


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