Substances in & out of a cell membrane

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Diffusion

This is how molecules move in & out of a cell membrane.

The molecules move from an area of high concentration to an area of low concentration.

No energy is needed in diffusion.

This is how oxygen & glucose gets into the cell.

This is how carbon dioxide, water & urea leave the cell.

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Visking Tube

This is a plastic tube that acts as a semi-permeable membrane and allows small molecules in & out.

The small molecules can pass through if they are small enough to pass through the pores while travelling with water.


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Osmosis

This is the movement of water from an area of high concentration to an area of low concentration through a semi-permeable membrane.

Water can move across all cell membranes.

For osmosis to happen there has to be 2 solutions of different concentrations & a partically permeable membrane to separate them.

If the concentations are the same inside & outside the cell, there is still the movement of water but no net osmosis (equilibrium).

If the cell membrane is damaged osmosis/diffusion/active transport cannot happen & the cell dies.

In a plant osmosis takes place at the root hairs.

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Active Transport

The dissolved molecules move from an area of low concentration to an area of high concentration through a semi-permeable membrane.

Because active transport goes against the concentration gradient, energy is needed.

The molecules that are transported in active transport is minerals, salt & sugar.

The glucose moves in the blood.

In plants, the minerals move into the root hairs.

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