Question

Consider the following statements and choose the correct answer.

I. Carrier proteins are needed by both facilitated diffusion and active transport and are sensitive to inhibitors that react with the protein.

II. Different types of proteins present in the membrane play a major role in both active as well as passive transport.

III. The carrier proteins needed by facilitated and active transport are specific.

IV. There is no need of energy to pump molecule against a concentration gradient in active transport.

V. Transport rate reaches the saturation point when all the active proteins are used.

• A. I, II, III, IV and V
• B. I, II and III
• C. V, IV and I
• D. I, II, III and V.

Answer 1

The correct option is D

I, II, III and V.

Carrier proteins are present in the membrane for carrying substances which cannot cross the membrane by themselves. The carrier proteins are required for both facilitated diffusion and active transport. There are different carrier proteins in the membrane, each is specific to a particular substance that they carry. Each type of carrier protein reaches a saturation point when all the carrier molecules are being used. Facilitated diffusion takes place along the concentration gradient, while active transport happens against the concentration gradient. Hence, an input of energy is required for active transport while none is required for facilitated diffusion.