Why does active transport require energy to move molecules of a substance across a cell membrane? A Lack of the substance makes the cell weak The substance moves from low to high concentration, against the concentration gradient The cell membrane is very thick . The substance moves from high to low concentration , with the concentration gradient

Answer 1

Active transport requires energy because the substance is being moved from an area of low concentration to an area of high concentration, which is against the concentration gradient. This process is not spontaneous and therefore requires cellular energy, typically in the form of ATP, to enable the transport proteins to move molecules against the gradient.

So, the correct explanation is: The substance moves from low to high concentration, against the concentration gradient.