The plasma membrane is best described as:
- a) a phospholipid bilayer surrounding the cell
This description is accurate because the plasma membrane is primarily made up of a double layer of phospholipids with embedded proteins, creating a flexible barrier that surrounds the cell. The hydrophilic (water-attracting) heads of the phospholipids face outward, towards the aqueous environments both inside and outside the cell, while the hydrophobic (water-repelling) tails face inward, away from the water. This unique structure is essential for the membrane’s functions, including transport, signaling, and maintaining the integrity of the cell.
The other options do not accurately describe the plasma membrane:
- b) a membrane composed of tiny shelves or cristae – This refers to the inner mitochondrial membrane, not the plasma membrane.
- c) a double layer of protein enclosing the plasma – This is incorrect; the plasma membrane is primarily composed of phospholipids, not just proteins.
- d) a single layered membrane that surrounds the nucleus – This describes the nuclear membrane, which is different from the plasma membrane.