What is the cell membrane primarily composed of?

• A. Cholesterol layer
• B. Carbohydrate mesh
• C. Phospholipid bilayer
• D. Protein lattice

Answer: (C)

The main idea here is that the cell membrane’s basic framework is a phospholipid bilayer. In water, phospholipids arrange into two layers with hydrophilic heads facing outward toward the watery environment and hydrophobic tails tucked inside, creating a flexible, semi-permeable barrier that keeps the cell’s contents in and the outside world out. Cholesterol sits within this bilayer to help regulate fluidity and stability, but it doesn’t form the entire structure. Proteins are embedded in or associated with the membrane to perform transport, signaling, and enzymatic tasks, and carbohydrates are mostly on the outer surface attached to lipids or proteins for cell recognition. So the phospholipid bilayer is the primary component that makes up the membrane.