Question

The plasma membrane is _________.
1. Selectively permeable
2. Fully permeable
3. Partially permeable
4. Impermeable
5. Both 1 and 3

Answer 1

Correct Answer - Option 1 : Selectively permeable

The correct answer is Selectively permeable.

• Selectively permeable means a membrane allows the passage of some molecules or ions and inhibits the passage of others. The capacity to filter molecular transport in this manner is called selective permeability. This is also called differential permeability.
• The plasma membrane is selectively permeable because hydrophobic molecules and small polar molecules can diffuse through the lipid layer, but ions and large polar molecules cannot. Integral membrane proteins enable ions and large polar molecules to pass through the membrane by passive or active transport.

• Other types of membranes on the basis of permeability:
  • Impermeable membrane: Substances of any type can not pass through them.
  • Permeable membranes: Substances of any type can pass through them.
  • Semi-permeable membrane: These are the membrane which permits the movement of only solvent molecules through them.