Why does active transport require energy to move molecules of a substance across a cell membrane?

Question

A. Lack of the substance makes the cell weak
B. The substance moves from low to high concentration against the concentration gradient
C. The cell membrane is very thick
D. The substance moves from high to low concentration with the concentration gradient

Answer 1

The correct answer is B. The substance moves from low to high concentration against the concentration gradient.

Active transport is a process that requires energy because it involves moving molecules against their concentration gradient, meaning from an area of lower concentration to an area of higher concentration. This requires the input of energy, usually in the form of ATP, to facilitate the movement of these molecules across the cell membrane.