AP BIOLOGY

Detailed explanation-1: -A membrane transport protein (or simply transporter) is a membrane protein involved in the movement of ions, small molecules, and macromolecules, such as another protein, across a biological membrane.

Detailed explanation-2: -Ion channels are macromolecular protein complexes spanning the lipid bilayer of the cell membrane Hille (2001). Up to 30% of the energy generated by the cell is used to maintain a concentration gradient of ions across the membrane.

Detailed explanation-3: -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-4: -A transport protein completely spans the membrane, and allows certain molecules or ions to diffuse across the membrane. Channel proteins, gated channel proteins, and carrier proteins are three types of transport proteins that are involved in facilitated diffusion.