AP BIOLOGY

Detailed explanation-1: -Facilitated diffusion is the passive movement of molecules along the concentration gradient. It is a selective process, i.e., the membrane allows only selective molecules and ions to pass through it. It, however, prevents other molecules from passing through the membrane.

Detailed explanation-2: -Pinocytosis (literally, “cell drinking”) is a form of endocytosis in which a cell takes in small amounts of extracellular fluid.

Detailed explanation-3: -During active transport, substances move against the concentration gradient, from an area of low concentration to an area of high concentration. This process is “active” because it requires the use of energy (usually in the form of ATP).

Detailed explanation-4: -Only the smallest molecules like water, carbon dioxide, and oxygen can freely diffuse across cell membranes. Larger molecules or charged molecules often require an input of energy to be transported into the cell.