4.4 Active Transport

%%The movement of molecule sin or out of the cell from a region of low conc. to high conc. using ATP and carrier proteins%%
Metabolic %%energy from ATP%% is needed
Substances moved %%against conc. gradient%%
%%Carrier proteins%% act as pumps
Every carrier protein is unique to each type of molecule that needs to be transported across a membrane. The sodium/potassium pump is one of the most common carrier proteins.

Carrier proteins span whole membrane and bind to molecule or ion to be transported
%%Molecule or ion binds to receptor site on carrier protein%%
On inside of cell/organism, %%ATP binds to protein which hydrolyses it into ADP and Pi%%
As a result, %%protein changes shape%% and %%opens to opposite side of membrane%%
%%Molecule/ion released on other side of membrane%%
%%Pi released from protein so returns to original shape to repeat process%%
%%Pi and ADP re-join via respiration%%

Sometimes more than 1 molecule is moved, either in the same or different directions
e.g. sodium potassium pump, sodium ions are moved out of cells as potassium ions are moved in