Veterinary Biochemistry- ICAR JRF/SRF 2024

• Dextran Linkages: Dextran is a complex, branched glucan polymer synthesized from sucrose by lactic acid bacteria (e.g., Leuconostoc mesenteroides):
• Major Linkages: The linear polysaccharide backbone consists predominantly of $\alpha(1\to 6)$ glycosidic linkages ($\gt 95\%$ of bonds).
• Branch Points: Minor branches are attached via $\alpha(1\to 3)$, $\alpha(1\to 2)$, or $\alpha(1\to 4)$ linkages.
• Clinical Application: Used as a plasma volume expander and in Sephadex gel filtration chromatography matrices.

Correct option: (2) a1-6 linkages

• Glycosaminoglycans (GAGs): Long, unbranched heteropolysaccharides consisting of repeating disaccharide units composed of an amino sugar and an uronic acid:
• Hyaluronic Acid: A classic non-sulfated GAG consisting of alternating units of D-glucuronic acid and $N$-acetylglucosamine linked by $\beta(1\to 3)$ and $\beta(1\to 4)$ bonds. It is found in synovial fluid, vitreous humor, and connective tissues.
• Other Choices: Cellulose is a structural plant glucan, peptidoglycan is a bacterial cell wall polymer, and inulin is a plant storage fructosan.

Correct option: (1) Hyaluronic acid

• Plasmalogens: A specialized subclass of ether glycerophospholipids characterized by a vinyl ether (alkenyl) bond at the $sn-1$ position of glycerol:
• Tissue Localization: Plasmalogens are especially abundant in brain and nervous tissue (comprising $\sim 50\text{--}60\%$ of ethanolamine phospholipids in myelin sheath) and in cardiac and skeletal muscle tissues.
• Function: They serve as structural components of cellular membranes, protect against oxidative stress by scavenging reactive oxygen species, and modulate membrane vesicle fusion.

Correct option: (1) Brain and Muscle tissues