AP BIOLOGY

Detailed explanation-1: -The small intestine is the primary site of amino acid and glucose absorption into the blood. These solutes are transported by three processes: simple diffusion, facilitated diffusion, and “active” transport.

Detailed explanation-2: -Facilitated diffusion therefore allows polar and charged molecules, such as carbohydrates, amino acids, nucleosides, and ions, to cross the plasma membrane. Two classes of proteins that mediate facilitated diffusion are generally distinguished: carrier proteins and channel proteins.

Detailed explanation-3: -Nutrients such as glucose and amino acids are transported, absorbed by various transporters embedded on the membranes of these enterocytes. Metabolism occurs in each cell along the crypt-villus axis (CVA).

Detailed explanation-4: -The GLUTs transport glucose across the plasma membrane by means of a facilitated diffusion mechanism.