AQA AS Biology Unit 1: Active Transport

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  • Created on: 22-08-13 16:07
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Active Transport
Active transport allows cells to exchange molecules against a concentration gradient.
Metabolic energy is required for the process.
Once inside the cell the molecules are prevented from leaking back by the barrier of the cell-
surface membrane's bilayer.
In this way a different environment is maintained on either side of the membrane.
Active Transport The movement of molecules or ions into or out of a
cell from a region of lower concentration to a region
of higher concentration using energy and carrier
molecules
It differs from passive forms of transport in the following ways:
Metabolic energy in the form of ATP is needed
Materials are moved against a concentration gradient
Carrier protein molecules which act as pumps are involved
The process is very selective, with specific substances being transported
Active transport uses ATP in one of two ways:
By using ATP directly to move molecules
By using a direct concentration gradient that has already been set up by direct active
transport

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Direct active transport of a single molecule or ion takes place as follows:
The carrier proteins span the cell-surface membrane and accept the molecules or
ions to be transported on one side of it
The molecules or ions bind to receptors on the channels of the carrier protein
On the inside of the cell, ATP binds to the protein, causing it to split into ATP and a
phosphate molecule
The protein molecule changes shape and opens to the opposite side of the
membrane
The phosphate…read more

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