Biology 3.8 Active Transport

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…