GENERAL KNOWLEDGE

Detailed explanation-1: -Chemically, cell membrane or plasma membrane is composed of proteins (20-70 %), lipids (20-79 %), carbohydrates (1-5 %) and water (20 %). Nucleic acids, i.e., DNA and RNA are absent.

Detailed explanation-2: -Carbohydrates are the third major component of plasma membranes. They are always found on the exterior surface of cells and are bound either to proteins (forming glycoproteins) or to lipids (forming glycolipids). These carbohydrate chains may consist of 2–60 monosaccharide units and may be either straight or branched.

Detailed explanation-3: -Carbohydrates in Cell Membranes Glycolipids are membrane carbohydrates linked to lipids. They account for 5% of the lipids in the cell membrane. There are three types of glycolipids: glycosphingolipids, glycoglycerolipids, and glycophosphatidylinositols. These carbohydrate chains help in cell-to-cell recognition.

Detailed explanation-4: -Which of the following is true of the carbohydrateportion of the cell membrane-a)It contributes to the polycationic chargeon the extracellular surfaceb)It is 1% of plasma membranec)It is found primarily in the form of freesaccharide groupsd)It has a symmetric distributionsCorrect answer is option ‘B’.