Veterinary Physiology- ICAR JRF/SRF 2024

• Coenzymes in Cellular Metabolism:
• NAD (Nicotinamide Adenine Dinucleotide): Pyridine nucleotide coenzyme derived from vitamin $B_3$ (niacin), functioning as an electron carrier.
• FAD (Flavin Adenine Dinucleotide): Flavin nucleotide coenzyme derived from vitamin $B_2$ (riboflavin), functioning in oxidation-reduction reactions.
• LDH (Lactate Dehydrogenase) is a full catalytic protein (enzyme).
• Proline is an imino/amino acid.
• nalysis:
• ((A) and (B) only): Correct coenzymes.

Correct option: (2) (A) and (B) only.

• Evaluation of Statements:
• Assertion (A): Hormones bind to receptors present on the cell surface or inside the cells.
• True. Hydrophilic hormones (peptides, catecholamines) bind to transmembrane cell-surface receptors (GPCRs, RTKs), while lipophilic hormones (steroids, thyroid hormones) cross the plasma membrane to bind intracellular cytoplasmic or nuclear receptors.
• Reason (R): All hormones are protein in nature.
• False. Hormones exhibit diverse chemical structures:

• Steroid hormones (estrogens, progesterone, testosterone, cortisol, aldosterone) are lipids derived from cholesterol.
• Amine hormones (epinephrine, norepinephrine, thyroxine, melatonin) are derived from single amino acids (tyrosine, tryptophan).
• Eicosanoids (prostaglandins) are derived from fatty acids.
  • Therefore, claiming all hormones are protein in nature is false.

• nalysis:
• ((A) is correct but (R) is not correct): Correct.

• Enzyme Classes in the EC Classification System:
• The International Union of Biochemistry and Molecular Biology (IUBMB) classifies all enzymes into six primary hierarchical classes (EC 1 to EC 6):

• EC 1: Oxidoreductases
• EC 2: Transferases (B)
• EC 3: Hydrolases (A)
• EC 4: Lyases
• EC 5: Isomerases (C)
  6. EC 6: Ligases (D)
  (EC 7 Translocases was added subsequently).
  • nalysis:

• All four listed groups (A, B, C, D) are official major enzyme classes. Hence, Option 3 is correct.