Which molecules primarily make up the cell membrane (lipid bilayer) in most cells?

• A. Cellulose fibers cross-linked with peptidoglycan and chitin
• B. Phospholipids arranged in a bilayer, with embedded proteins and cholesterol (in many animal cells)
• C. A single layer of triglycerides with dissolved DNA and RNA
• D. Glycogen polymers coated with histones and enzymes

Answer: (B)

Verified step by step guidance

1. Understand that the cell membrane, also known as the plasma membrane, is primarily composed of a lipid bilayer that provides a flexible yet sturdy barrier around the cell.
2. Recall that the main lipid molecules forming this bilayer are phospholipids, which have hydrophilic (water-attracting) heads and hydrophobic (water-repelling) tails, causing them to arrange in two layers with tails facing inward and heads facing outward.
3. Recognize that embedded within this phospholipid bilayer are various proteins that serve functions such as transport, signaling, and structural support.
4. Note that in many animal cells, cholesterol molecules are interspersed within the bilayer to modulate membrane fluidity and stability.
5. Eliminate other options by understanding that cellulose fibers, peptidoglycan, chitin, triglycerides, DNA, RNA, glycogen, and histones are not the primary structural components of the cell membrane but serve other roles in the cell.