movement across p.m
- uses energy, transports substances up there conc gradient.
- the protien binds a moelcule of the substance to be transported on one side of the membrane changes shape and releases it on the toher side.
ATP in a.y:
- ATP is synthesised from ADP and phosphate.
- sodium/potassium pump continually uses ATP to actively pump sodium ions out of the cell and potassium ions into the cell. creates ion gradients, which can be used to regulate w.p and drive ither proceses.
effect of conc difference on rate of transport:
- lipid diffusion = + conc difference + rate of diffusion.
- f.d = + conc rate is limited.
- a.t = + rate even when there is no conc diff.
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