Question

In active transport, carrier proteins are used which use energy in the form of ATP to

• A. Transport molecules against the concentration gradient across the cell wall
• B. Transport molecules along the concentration gradient across the cell membrane
• C. Transport molecules against the concentration gradient across the cell membrane.
• D. Transport molecules along the concentration gradient across the cell wall.

Answer 1

The correct option is C

Transport molecules against the concentration gradient across the cell membrane.

Diffusion usually involves the transport of substances from a region of higher concentration to a region of lower concentration, which is along the concentration gradient and requires no energy. The question mentions active transport and also the expenditure of ATP. Since there is no expenditure of ATP when molecules are transported along the concentration gradient, you can easily say that ATP is required only when molecules are transported against the concentration gradient. This eliminates options B and D.
The cell wall has no carrier proteins and only cell membrane has carrier proteins, hence you can choose the answer as option C.