If a cell is bathed in an extracellular solution higher in Na⁺ concentration than the cytoplasm, it will use _______ to maintain its normal intracellular concentration of Na⁺. A) active transport against the concentration gradient of Na⁺ B) simple diffusion as the primary means of Na⁺transport C) secondary active transport for passive diffusion of Na⁺ D) carrier proteins to increase the rate of Na⁺ diffusion E) facilitated diffusion to pump Na⁺ ions out of the cell

Question

Quizplus · Accepted Answer

Active transport is necessary to move Na⁺ ions against their concentration gradient from a region of lower concentration (cytoplasm) to a region of higher concentration (extracellular solution). Simple diffusion (B), facilitated diffusion (E), and carrier proteins (D) all work in the direction of the concentration gradient and would not be effective in maintaining a normal intracellular concentration of Na⁺ in this situation. Secondary active transport (C) involves the use of an electrochemical gradient and would not be necessary in this case as there is already a concentration gradient.

If a Cell Is Bathed in an Extracellular Solution Higher