AP BIOLOGY

Detailed explanation-1: -Carrier proteins are responsible for the facilitated diffusion of sugars, amino acids, and nucleosides across the plasma membranes of most cells.

Detailed explanation-2: -Channel proteins, gated channel proteins, and carrier proteins are three types of transport proteins that are involved in facilitated diffusion. A channel protein, a type of transport protein, acts like a pore in the membrane that lets water molecules or small ions through quickly.

Detailed explanation-3: -In facilitated diffusion, substances move into or out of cells down their concentration gradient through protein channels in the cell membrane.

Detailed explanation-4: -Channel proteins provide an open channel or passageway through the cell membrane for molecules to move across. Many channel proteins allow the diffusion of ions. Ions are charged atoms. The charge makes it difficult to cross the cell membrane without assistance.

Detailed explanation-5: -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).