Question

Read the statements given below carefully and determine their validity by choosing the correct option.
I. Carrier proteins are used in active transport.
II. These carrier proteins use ATP to transport molecules along the concentration gradient of cell membrane.

• A. Both I and II are correct and II is the correct explanation of I.
• B. Both I and II are correct, but II is not the correct explanation of I.
• C. I is correct but II is wrong.
• D. Both I and II are wrong.

Answer 1

The correct option is C I is correct but II is wrong.

A type of specialised protein that helps in the movement of substances across the membrane by changing its conformation are called carrier proteins.
In active transport, they use energy in the form of ATP to transport molecules against the concentration gradient (from a region of lower concentration to a region of higher concentration). Transportation rate reaches maximum when all carrier proteins are being used or are saturated. These proteins are very specific to certain substances and are sensitive to inhibitors. Carrier proteins that are involved in facilitated diffusion also helps in the transport of substances across the membrane by changing their conformation. However, in facilitated diffusion the movement of substances is along the concentration gradient (from a region of higher concentration to a region of lower concentration). Thus ATP is not utilized in facilitated diffusion.