Biology Unit 3

Summary of Unit 3 Biology, Triple Science.

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Gas and Solute Exchange

Exchange surfaces are ADAPTED to maximise effectiveness.

Carbon dioxide diffuses into the air spaces within a leaf (stomata), then it diffuses into cells where photosynthesis happens.

Water vapour and oxygen diffuse out through the stomata.

The size of the stomata are controlled by guard cells.

Diffusion = particles move from an area of high concentration to an area of low concentration

Osmosis = similar to Diffusion, but only in water. The water moves across a partially permeabl membrane.

Active transport = goes against the concentration gradient. Eg. from an area of low concentration to an area of high concentration.

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