Biology b4

revision for topic homeostasis

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Homeostasis 1

Homeostasis-maitanence of a constant internal enviroment within the body. receptor-effects a change in the body. processing centre-the brain co-ordinates what to do. effector-produces the response.

diffusion-dissolved substances have to pass through the partially permeable cell membrane to get into or out to a cell diffusion is one of the processes that allows this to happen the particles move from were they arein a high concentration to were there in a less concentration THE BIGGER THE CONCENTRATION GRADIENT THE FASTER THE SPEED OF DIFFUSION.diffusion only occurs in gases and liquids diffusion stops when both sides are equal.osmosis- the diffusion of WATER across a partially permeable membrane. a solution that has a high concentration of water molecules is a dilute solution.water moves from where it is in a high concentration to where it is in a low concentration.water moves from a dilute solution to a more concentrated solution.

 osmosis in palnts and animals- water moves into a plant cell the cell wall stops the cell from bursting.we say the cell is turgid.this is useful as it gives the cell support. water moving out of plant-when water moves out of the plant cell vacuole by osmosis it becomes flaccid. flaccid vacuole is much smaller and taking up less space.if alot of water leaves the cell the cytoplasm starts to peel away from the cell wall and we say the cell has undergone PLASMOLYSIS      

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