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Active transport
Active transport is the movement of substances
against the concentration gradient
This means that the substance is moving from a
lower concentration to a higher.
Since it is not passive, this movement will
require energy.
It is only worth using this energy for the cell if
the substance is needed.…read more

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Exchange of gases in the lungs
The lungs exchange oxygen (necessary for
aerobic respiration) and CO2 (waste product of
Adaptations being: moist to make diffusion easier,
large surface area to increase diffusion, and thin
walls as above.
Oxygen moves into blood by diffusion, and CO2
moves back to the lungs…read more

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Exchange in the gut
Food is broken down into small soluble
molecules which are absorbed into the blood.
Villi increase the surface area so as to absorb
these molecules.
Food is absorbed by both diffusion and active
transport, depending on the concentration of the
food solute in the blood.…read more

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Exchange in other creatures
Most creatures have similar adaptations to
exchange efficiently
Large surface area
Gases transported away quickly so as to keep a
high concentration gradient
Thin membranes to increase rate of diffusion.…read more

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Exchange in Plants
Gases diffuse in and out of plants through the
guard cells, `stomata'.
Needed Waste Product
Photosynthesis CO2 Oxygen
Respiration Oxygen CO2
The movement depends on which process is
happening fastest.
Adaptations... Thin, root hairs (like villi), internal
air spaces…read more

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