Which of the Following Membrane Activities Require Energy from ATP

Question

Which of the following membrane activities require energy from ATP hydrolysis?
A)facilitated diffusion of chloride ions across the membrane through a chloride channel
B)movement of water into a cell
C)Na⁺ ions moving out of a mammalian cell bathed in physiological saline
D)movement of glucose molecules into a bacterial cell from a medium containing a higher concentration of glucose than inside the cell
E)movement of carbon dioxide out of a paramecium

Accepted Answer

Na⁺ ions moving out of a mammalian cell bathed in physiological saline requires energy from ATP hydrolysis because it is moving against its concentration gradient. This is an example of active transport, which requires energy input. The other activities listed do not require ATP hydrolysis, as they either involve movement down a concentration gradient (A, D) or movement of a small, uncharged molecule (B, E).