Entrance Exams
Govt. Exams
The Ramachandran plot shows allowed and disallowed combinations of φ and ψ angles for the polypeptide backbone, used to verify the stereochemical quality of 3D protein structures.
Kwashiorkor results from severe protein malnutrition involving deficiency of all essential amino acids, leading to loss of muscle mass and edema despite adequate calorie intake.
In competitive inhibition, the inhibitor competes with substrate for the active site. This increases the apparent Km (requires more substrate to reach half-maximal velocity) while Vmax remains unchanged.
Peptide bonds form through a condensation reaction between the carboxyl group (-COOH) of one amino acid and the amino group (-NH2) of another, releasing H2O. They are covalent and stable.
ER chaperones like BiP (heat shock protein 70) assist in protein folding, prevent aggregation, and aid in proper disulfide bond formation during synthesis.
LDH catalyzes the interconversion of lactate and pyruvate using NAD+ as an electron acceptor and NADH as an electron donor in the coupled redox reaction.
Collagen triple helix is stabilized by hydrogen bonds between the three polypeptide chains and covalent cross-links (lysine and hydroxylysine residues) between molecules, providing mechanical strength.
Leucine is a nonpolar, hydrophobic amino acid with an isobutyl side chain. Serine and threonine are polar uncharged, while aspartate is acidic and polar.
Denaturation is disruption of non-covalent interactions (hydrogen bonds, hydrophobic interactions, ionic bonds) that maintain higher-order structures. Peptide bonds (primary structure) remain intact. Some proteins can refold (renature) if conditions permit, as demonstrated by Anfinsen's ribonuclease experiments.
The Cori cycle (glucose-lactate cycle) allows muscles undergoing anaerobic glycolysis to produce lactate, which is transported to liver and converted back to glucose via gluconeogenesis, maintaining blood glucose homeostasis during intense exercise.