Question

which of the following correctly describes the structural organization of the cell membrane?
a bilayer of phospholipid molecules in which protein molecules are embedded and can move
three layers: lipid on the inside, protein in the middle, and carbohydrates (and polysaccharides) on the outside
a solid, rigid layer of phospholipid with loosely bound protein molecules
rigid layers of protein molecules in which carbohydrate molecules are suspended

Explanation:

The cell membrane is described by the fluid - mosaic model. According to this model, the cell membrane is a bilayer of phospholipid molecules (with hydrophilic heads and hydrophobic tails). Protein molecules are embedded in this bilayer and can move (lateral movement is possible).

• Option B is incorrect as the cell membrane is not a three - layer structure with lipid - protein - carbohydrate (in that order). Carbohydrates are mainly on the outer surface but not in a separate distinct layer as described.
• Option C is wrong because the cell membrane is not a solid, rigid layer. The phospholipids have some fluidity.
• Option D is incorrect as the cell membrane is not made of rigid protein layers with suspended carbohydrate molecules.

Answer:

A. A bilayer of phospholipid molecules in which protein molecules are embedded and can move