Question

The most important function of a cell membrane is that it

• A. Controls the entry and exit of materials from the cells.
• B. Controls only the entry of materials into the cells.
• C. Controls only the exit of materials from the cells.
• D. Allows entry and exit of materials without any control.

Answer 1

The correct option is A Controls the entry and exit of materials from the cells.

The cell membrane acts as a selective barrier for the entry and exit of the material. The proteins present in the cell membrane are specific to the material and they allow the entry or exit either according to the concentration gradient, for example, channel and carrier proteins or against the concentration gradient through the use of energy, for example, pump proteins. The lipid bilayer prevents the entry and exit of polar and large-sized material.

Hence, the correct answer is 'Controls the entry and exit of material from the cells'.