Question

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

Answer 1

Answer:

The substance moves from low to high concentration, against the concentration gradient.

Explanation:

When molecules move from high to low concentration, it is known as Diffusion. It moves with the concentration gradient and does not require energy.

However, when molecules move from low to high concentration, it is against the concentration gradient and cannot proceed without Energy. This process is called Active transport.

Cell membrane is not thick, it is thin and semi permeable.