Question

Facilitated Diffusion across a cell membrane refers to:

• A. Molecules and ions diffuse to cross a membrane through active transport
• B. Molecules and ions diffuse passively with the help of transport proteins
• C. The hydrophilic passage ways of proteins prevent the water molecules to diffuse
• D. Molecules and ions diffuse with the help of energy provided by a concentration gradient

Hint:

Facilitated diffusion: passive + transport proteins. Active transport: requires ATP. Simple diffusion: no proteins needed.

Answer 1

The Correct Option is B

Step 1: Concept
Facilitated diffusion: passive membrane transport via protein channels or carriers.

Step 2: Meaning
Molecules move down their concentration gradient through specific transport proteins, without requiring ATP.

Step 3: Analysis
(A) is incorrect: active transport requires energy. (C) is incorrect: aquaporins allow water movement, not prevent it. (D) is misleading: the concentration gradient provides the driving force but no metabolic energy is consumed. (B) correctly describes facilitated diffusion.

Step 4: Conclusion
Facilitated diffusion is passive (no ATP required) and assisted by transport proteins. Final Answer: (B)