Question

Which one of the following is active transport?

(a) It is the movement of a substance against a diffusion gradient with the use of energy from respiration

(b) It is the movement of a substance against a diffusion gradient without the use of energy

(c) It is the movement of a substance against a diffusion gradient with the use of energy from photosynthesis

(d) It is the movement of a substance along a diffusion gradient with the use of energy from respiration

Answer 1

(a) It is the movement of a substance against a diffusion gradient with the use of energy from respiration

Active transport is the movement of molecules across a membrane, from a region of their lower concentration to a region of their higher concentration, i.e. aganist the diffusion or concentration gradient.

Active transport always requires cellular energy to achieve this movement.