Question

In fluid mosaic model of plasma membrane

• A. Upper layer is non-polar and hydrophilic
• B. Polar layer is hydrophobic
• C. Phospholipids form a bimolecular layer in middle part
• D. Proteins form a middle layer

Answer 1

The Correct Option is C

Chemically a biomembrane consists of lipids (20-70%), proteins (20-70%), carbohydrates (1-5%) and water (20%). The important lipids of the membrane are phospholipids (some hundred types), sterols, (e.g. cholesterol), glycolipids, sphingolipid (e.g., sphingomyelin, cerebrosides). Protein can be fibrous or globular structural carrier, receptor or enzymatic. The lipid molecules are amphiatic or amphipathic, that is, they possess both polar hydrophilic (water loving) and non-polar hydrophobic (water repelling) ends. The hydrophilic region is in the form of head while hydrophobic part contains two tails of fatty acids. It results in formation of a lipid bilayer. Most common lipid of the bilayer is phospholipids. Protein molecules also possess both polar and non-polar side chains. Usually their poly hydrophilic linkages are towards the outer side. The non-polar or hydrophobic linkage are either kept folded inside or used to establish connections with hydrophobic parts of the lipids.