All of the following involve active transport across membranes except
A) the movement of mineral nutrients from the apoplast to the symplast.
B) the movement of sugar from mesophyll cells into sieve-tube elements.
C) the movement of sugar from one sieve-tube element to the next.
D) the movement of K⁺ across guard cell membranes during stomatal opening.
E) the movement of mineral nutrients into cells of the root cortex.

Question

Quizplus · Accepted Answer

The movement of sugar from one sieve-tube element to the next involves passive transport, specifically facilitated diffusion through plasmodesmata, not active transport. Active transport requires energy to move substances against their concentration gradient, which is not the case for the movement between sieve-tube elements.

All of the Following Involve Active Transport Across Membranes Except