Active transport allows cells to exchange molecules against a concentration gradient.
Metabolic energy required.
Once inside a cell, molecules prevented from leaking back by cell-surface membrane's bilayer.
What is active transport?
= Movement of molecules or ions into or out of a cell from region of lower conc. to region of higher conc. using energy and carrier molecules.
NB: Carrier proteins = specific tertiary structure, only transport particular substances. They are not enzymes and do not have active sites.
For active transport:
- ATP (metabolic energy is needed).
- Materials moved against conc. gradient.
- Carrier protein molecules that act as pumps used.
- Process is very selective.
ATP used in two ways:
- Using ATP directly to move molecules.
- Conc. gradient that…