Which of these biomolecules is an essential component of the plasma membrane?
ACellulose
BPhospholipids
CDNA
DGlycogen
Answer:
B. Phospholipids
Read Explanation:
- Phospholipids are the primary structural components of the plasma membrane, forming a phospholipid bilayer that acts as a semi-permeable barrier.
- Each phospholipid molecule consists of a hydrophilic (water-loving) head containing a phosphate group and two hydrophobic (water-fearing) fatty acid tails.
- In the aqueous environment of the cell, these molecules spontaneously arrange themselves into a bilayer where the hydrophobic tails face inward, away from water, while the hydrophilic heads face outward toward the intracellular and extracellular fluids.
- This organization is described by the Fluid Mosaic Model, proposed by S.J. Singer and G.L. Nicolson in 1972.
- Besides phospholipids, the plasma membrane includes:
- Cholesterol: Embedded between phospholipids to regulate membrane fluidity and stability.
- Integral Proteins: Span across the bilayer to facilitate transport and signaling.
- Peripheral Proteins: Loosely attached to the inner or outer surface, often serving as enzymes or structural supports.
- Carbohydrates: Attached to proteins (glycoproteins) or lipids (glycolipids) on the extracellular side, playing a key role in cell-to-cell recognition.
- The amphipathic nature of phospholipids—having both hydrophobic and hydrophilic regions—is essential for maintaining the integrity and selective permeability of the cell membrane.