Practicing Success

Target Exam

CUET

Subject

Biology

Chapter

Cell : The Unit of Life

Question:

Molecules which are transported across the membrane against their concentration gradient, i.e. from the lower to higher concentration. Such a transport is called : 

Options:

Active transport, e.g., diffusion.

Passive transport, e.g., diffusion.

Active transport, e.g., Na+/K +pump.

Osmosis, a type of simple diffusion.

Correct Answer:

Active transport, e.g., Na+/K +pump.

Explanation:

The correct answer is Option (3) –Active transport, e.g., Na+/K +pump.

One of the most important functions of the plasma membrane is the transport of the molecules across it. The membrane is selectively permeable to some molecules present on either side of it. Many molecules can move briefly across the membrane without any requirement of energy and this is called the passive transport. Neutral solutes may move across the membrane by the process of simple diffusion along the concentration gradient, i.e., from higher concentration to the lower.

Water may also move across this membrane from higher to lower concentration. Movement of water by diffusion is called osmosis. As the polar molecules cannot pass through the nonpolar lipid bilayer, they require a carrier protein of the membrane to facilitate their transport across the membrane.

A few ions or molecules are transported across the membrane against their concentration gradient, i.e., from lower to the higher concentration. Such a transport is an energy dependent process, in which ATP is utilised and is called active transport, e.g., Na+/K+ Pump.