Which membrane encloses the cell?

• A. Cell membrane (plasma membrane)
• B. Nuclear envelope
• C. Cell wall
• D. Cytoplasm

Answer: (A)

The boundary that encloses the cell is the plasma membrane, also known as the cell membrane. It forms a phospholipid bilayer that surrounds the cytoplasm, creating the dividing line between the inside of the cell and the outside environment. Beyond just a barrier, it regulates what enters and leaves, supports cell signaling, and hosts membrane proteins involved in transport and communication.

The nuclear envelope, on the other hand, surrounds the nucleus, not the whole cell, keeping genetic material separate from the cytoplasm. The cell wall is a rigid outer layer found in plants, fungi, and many bacteria that provides support and protection but is not the membrane that encloses the cell’s interior. The cytoplasm is the internal substance of the cell—gel-like but not a membrane itself.

So, the membrane that encloses the cell is the plasma membrane.