Biochemistry - MCQ Practice Questions

What is the primary difference between competitive and non-competitive enzyme inhibition in terms of Vmax and Km?

Collagen, the most abundant protein in mammals, contains which unusual amino acid at every third position?

In protein synthesis, which aminoacyl-tRNA synthetase error rate is approximately 1 in 10,000, ensuring high fidelity?

Which of the following statements about allosteric enzymes is correct?

A patient with phenylketonuria (PKU) lacks functional phenylalanine hydroxylase. Which cofactor is essential for this enzyme's activity?

What is the primary function of protein phosphatase 2A (PP2A) in cellular signaling?

During protein folding, which molecular chaperone is primarily responsible for preventing aggregation and facilitating ATP-dependent unfolding in prokaryotes?

Which of the following proteases is secreted as an inactive zymogen and requires trypsin for its activation?

In the context of enzyme kinetics, what does the turnover number (kcat) represent?

Which post-translational modification is essential for the activation of blood clotting cascade and involves γ-carboxylation of glutamate residues?

What is the Hill coefficient (n) when it equals 1.0 in enzyme kinetics, and what does this indicate?

Which enzyme catalyzes the formation of peptide bonds during protein synthesis on the ribosome?

In the unfolded protein response (UPR), which transmembrane kinase/endonuclease senses ER stress and activates the IRE1 pathway?

Which of the following correctly describes the relationship between enzyme concentration and reaction velocity in zero-order kinetics?

What is the primary role of protein disulfide isomerases (PDI) in the endoplasmic reticulum?

Which amino acid residue, when present in the active site, typically acts as a general acid-base catalyst in serine proteases?

In the proteasome pathway, which E3 ubiquitin ligase specifically recognizes phosphorylated IκB and targets it for degradation, leading to NF-κB activation?

Which of the following statements about enzyme-substrate complex formation is correct according to transition state theory?

In hyperammonemia type 1, mutations in which enzyme lead to accumulation of ammonia and subsequent neurotoxicity?

Which type of enzymatic reaction does DNA ligase catalyze, and what cofactor is required?