AP BIOLOGY

Detailed explanation-1: -Passive transport does not require the cell to expend any energy and involves a substance diffusing down its concentration gradient across a membrane.

Detailed explanation-2: -In facilitated transport, also called facilitated diffusion, material moves across the plasma membrane with the assistance of transmembrane proteins down a concentration gradient (from high to low concentration) without the expenditure of cellular energy.

Detailed explanation-3: -Facilitated diffusion does not need any energy for the movement of molecules as they move from higher concentration to lower concentration gradient.

Detailed explanation-4: -Facilitated diffusion is the transport of substances across a biological membrane from an area of higher concentration to an area of lower concentration with the help of a transport molecule. Since substances move along the direction of their concentration gradient, chemical energy is not directly required.

Detailed explanation-5: -Simple diffusion does not require energy: facilitated diffusion requires a source of ATP.