(A) its uptake along the concentration gradient utilizing energy

(B) requirement of a carrier to support transport along the concentration gradient

(C) chemical modification of the solute during its uptake

(D) its uptake against the concentration gradient

Active transport moves solutes across cell membranes using energy, distinct from passive diffusion. This article explains Q.69 characteristics with the correct answer and all options for biology exam prep.

Correct Answer

The correct answer is (D) its uptake against the concentration gradient.

Active transport uses ATP energy to move solutes from low to high concentration areas, against their gradient—unlike passive transport. Examples include the Na+/K+ pump maintaining ion gradients essential for nerve impulses and homeostasis.

Option Breakdowns

(A) its uptake along the concentration gradient utilizing energy

Movement along (down) the gradient requires no energy; this describes facilitated diffusion, not active transport.​
Energy use defines active transport specifically for against-gradient movement.​

(B) requirement of a carrier to support transport along the concentration gradient

Carrier proteins aid both passive (facilitated diffusion) and active transport, but “along the gradient” excludes active transport.​
Active transport carriers work against gradients using energy.​

(C) chemical modification of the solute during its uptake

Active transport moves solutes unchanged; modification occurs in other processes like phosphorylation in signaling.​
No covalent changes to transported molecules like Na+, K+, or glucose.​

(D) its uptake against the concentration gradient

Defining feature: pumps like Na+/K+ ATPase hydrolyze ATP to drive ions uphill against gradients.
Enables cellular functions impossible by diffusion alone.​