What is Active Transport ?

by shyam Sun Jan 11, 2009 2:52 pm

What is Active Transport ?

I want to know something about it ????????

Exclamation

Hope anybody would not be sleeping and reply Sleep

by **admin @ shivam** Sun Jan 11, 2009 3:05 pm

Active Transport

Active transport is the pumping of molecules or ions through a membrane against their concentration gradient. It requires:

* a transmembrane protein (usually a complex of them) called a transporter and
* energy. The source of this energy is ATP.

The energy of ATP may be used directly or indirectly.

* Direct Active Transport. Some transporters bind ATP directly and use the energy of its hydrolysis to drive active transport.
* Indirect Active Transport. Other transporters use the energy already stored in the gradient of a directly-pumped ion. Direct active transport of the ion establishes a concentration gradient. When this is relieved by facilitated diffusion, the energy released can be harnessed to the pumping of some other ion or molecule.