Biochemistry
Metabolic pathways, enzymes, proteins
Showing 71–73 of 73 questions
In a double displacement enzyme reaction mechanism, the enzyme forms a covalent intermediate. Which protease follows this mechanism?
Correct Answer:
B. Serine proteases
EXPLANATION
Serine proteases (like trypsin, chymotrypsin) form an acyl-enzyme intermediate through a nucleophilic attack by the active site serine residue.
During protein synthesis, a missense mutation changes codon GAA to GUA. Which amino acid substitution occurs?
Correct Answer:
A. Glutamic acid to Valine
EXPLANATION
GAA codes for Glutamic acid (Glu), GUA codes for Valine (Val). This is a non-conservative substitution of a charged to hydrophobic residue.
A protein with multiple subunits shows cooperative binding of substrate. This phenomenon is best explained by:
Correct Answer:
B. Allosteric regulation
EXPLANATION
Cooperative binding (positive cooperativity) occurs when binding of one substrate molecule increases affinity for subsequent molecules, a classic example of allosteric regulation as seen in hemoglobin.