Question

Which one of the following classes of membrane protein requires ATP for transport of some specific ions or molecules across the cellular membranes?

• A. Ion channels
• B. Pumps
• C. Symporters
• D. Antiporters

Hint:

Primary active transport proteins such as pumps directly use ATP, whereas channels and most cotransporters generally use passive or secondary active transport mechanisms.

Answer 1

The Correct Option is B

Step 1: Understand membrane transport proteins.
Membrane proteins help transport ions and molecules across biological membranes. These transport systems may function either passively or actively depending on whether energy is required.

Step 2: Analyze ion channels.
Ion channels provide pores through which ions move along their concentration gradient. This process is passive and does not directly require ATP. Therefore, option (A) is incorrect.

Step 3: Analyze pumps.
Pumps are active transport proteins that use energy, usually from ATP hydrolysis, to move substances against their concentration gradient. Examples include the sodium-potassium pump and calcium pump. Hence, option (B) is correct.

Step 4: Analyze symporters.
Symporters transport two substances in the same direction. Most symporters use the energy stored in ion gradients rather than directly using ATP. Thus, option (C) is incorrect.

Step 5: Analyze antiporters.
Antiporters move two substances in opposite directions and generally depend on electrochemical gradients instead of direct ATP consumption. Therefore, option (D) is incorrect.

Step 6: Compare all transport systems.
Among the given options, only pumps directly utilize ATP for active transport across membranes.

Step 7: Final conclusion.
Hence, the membrane proteins that require ATP for transport are pumps.
\[ \boxed{\text{Pumps}} \]
Therefore, the correct answer is option (B).