AP BIOLOGY

Detailed explanation-1: -Carrier proteins and channel proteins are the two major classes of membrane transport proteins. Carrier proteins (also called carriers, permeases, or transporters) bind the specific solute to be transported and undergo a series of conformational changes to transfer the bound solute across the membrane (Figure 11-3).

Detailed explanation-2: -(See below.) Active transport uses carrier proteins, not channel proteins. These carrier proteins are different than the ones seen in facilitated diffusion, as they need ATP in order to change conformation.

Detailed explanation-3: -In secondary active transport, the movement of the sodium ions down their gradient is coupled to the uphill transport of other substances by a shared carrier protein (a cotransporter).

Detailed explanation-4: -In active transport, substances move against a concentration gradient across a cell membrane. Hence energy is required. The energy available in the body in the form of ATP is used to move this substance across the cell membrane.