GCSE AQA Biology Unit 3

A brief overview of GCSE AQA biology unit 3

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  • Created by: Hannah
  • Created on: 15-02-12 17:22

Gas and Solute Exchange, The Breathing System, Dif

Substances move by active transport, diffusion and osmosis

Active transport - where substances are absorbed against a concentration gradient

Diffusion - where particles move from an area of high concentration to an area of low concentration

Osmosis - where water moves across a partially permeable membrane from an area of high water concentration to an area of low water concentration

Exchange surfaces are adapted to maximise effectiveness

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The Breathing System

trachea > bronchi > bronchioles > alveoli

Breathing in:

1) intercostal muscles and diaphragm contract

2) thorax volume increases

3) this decreases the pressure, drawing air in

Breathing out:

1) intercostal muscles and diaphragm realax

2) thorax volume decreases

3) air is forced out

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Diffusion Through Cell Membranes

Features of exchange areas:

* an enormous surface area

* a moist lining for disolving gases

* very thin walls

* a single layer of surface cells

* a copious blood supply

* a very good blood supply to asssist quick absorption

You will need to know about gas exchange in the lungs and digestion in the small intestine.

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Active Transport

Active transport is where substances are absorbed against a concentration gradient.

You need to know about active transport in root hairs and the gut.

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Comments

Hannah

Hello,

I've made some revision cards for GCSE AQA biology unit 3. I will add to them as I learn more topics.

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