Question

Which of the following statement is irrelevant with regards to facilitated transport?

• A. It takes place by downhill transport.
• B. It is a highly selective process.
• C. Requires special membrane proteins.
• D. Requires ATP energy.

Answer 1

The correct option is D Requires ATP energy.

Hydrophilic substances (substances having high affinity to water) cannot diffuse across the plasma membrane, as their polarity makes it difficult to cross the phospholipid bilayer.

Specialized transport proteins found on the cell membrane shield these molecules making a hydrophilic tunnel for their passage. When the diffusion of these hydrophilic substances are facilitated by transport proteins it is called facilitated diffusion.

The movement of molecules in facilitated diffusion takes place from higher concentration to lower concentration (downhill transport) along the concentration gradient, without the expenditure of metabolic energy i.e. ATP.

Facilitated diffusion is highly specific and allows very selective substances for uptake.

Hence, of the statements given above, "requires ATP energy" is irrelevant statement with respect to facilitated diffusion.