Biology of Humans 4th Edition by Judith Goodenough,Betty McGuire

Exercise 17

Facilitated diffusion is
a. the random movement of a substance from a region of higher concentration to a region of lower concentration.
b. the movement of water across the plasma membrane.
c. the movement of molecules across the plasma membrane against a concentration gradient with the aid of a carrier protein and energy supplied by the cell.
d. the movement of a substance from a region of higher con- centration to a region of lower concentration with the aid of a membrane protein.