Question

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

Explanation:

The cell membrane is described by the fluid - mosaic model. It consists of a phospholipid bilayer. Phospholipids have hydrophilic heads and hydrophobic tails, forming a bilayer. Proteins are embedded in this bilayer and can move (lateral movement in most cases).

• Option A: The cell membrane is not rigid. Proteins are not the main structural layer in this incorrect description. Carbohydrates are not suspended in a protein - based rigid layer.
• Option B: The cell membrane is not structured as three such distinct layers (lipid - protein - carbohydrate).
• Option C: This matches the fluid - mosaic model of the cell membrane (phospholipid bilayer with embedded, mobile proteins).
• Option D: The cell membrane is not a solid, rigid layer. Phospholipids are in a fluid state (at physiological temperatures for most cells), and the description of protein binding is incorrect.

Answer:

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