Question 1

Which of the following best describes the role of a coenzyme in an enzymatic reaction?

Accepted Answer

A coenzyme acts as a non-protein organic molecule that assists enzymes by carrying chemical groups between molecules.

Question 2

Which of the following statements about enzyme specificity is correct?

Accepted Answer

Enzyme specificity is determined by the precise three-dimensional structure of the enzyme's active site.

Question 3

A biochemist determines the type of enzyme by studying the kinetics of the enzyme in the presence of a substrate. If the graph of initial velocity versus substrate concentration is hyperbolic, what does this indicate about the enzyme?

Accepted Answer

The enzyme follows Michaelis-Menten kinetics and likely has a single substrate binding site.

Question 4

Which of the following is NOT one of the six main classes of enzymes as classified by the Enzyme Commission?

Accepted Answer

Polymerases

Question 5

Which equation best describes the Michaelis-Menten relationship between initial velocity ($v_0$), maximum velocity ($V_{max}$), substrate concentration ($[S]$), and the Michaelis constant ($K_m$)?

Accepted Answer

$v_0 = \frac{V_{max} [S]}{K_m + [S]}$

Question 6

Which of the following best explains why allosteric enzymes often display sigmoidal (S-shaped) kinetic curves?

Accepted Answer

Allosteric enzymes have multiple subunits and exhibit cooperative binding of substrate.

Question 7

A patient is given a drug that acts as a competitive inhibitor of an enzyme. Which of the following changes would you expect to see in the enzyme kinetics?

Accepted Answer

$K_m$ increases, $V_{max}$ remains unchanged.

Question 8

Which of the following is a key difference between general acid-base catalysis and covalent catalysis in enzyme mechanisms?

Accepted Answer

General acid-base catalysis involves proton transfer, while covalent catalysis involves the formation of a transient covalent bond between enzyme and substrate.

Question 9

Which of the following statements about enzyme inhibitors is correct?

Accepted Answer

An allosteric inhibitor binds to a site other than the active site and decreases enzyme activity.

Question 10

A researcher observes that an enzyme-catalyzed reaction proceeds much faster in the presence of a cofactor. Which of the following best describes the role of the cofactor?

Accepted Answer

The cofactor is a non-protein molecule or ion that is required for the enzyme's activity.

Question 11

Which of the following best describes the induced fit model of enzyme action?

Accepted Answer

The enzyme changes its conformation upon substrate binding to better fit the substrate.

Question 12

Which of the following is an example of an oxidoreductase enzyme reaction?

Accepted Answer

Lactate dehydrogenase catalyzing the conversion of pyruvate to lactate.

Question 13

Which of the following statements about enzyme active sites is correct?

Accepted Answer

The active site is a specific region of the enzyme where substrate binding and catalysis occur.

Question 14

A mutation in an enzyme changes an amino acid residue in the active site from serine to alanine. Which of the following is the most likely effect on enzyme function?

Accepted Answer

The enzyme's catalytic activity may decrease due to loss of a functional group involved in catalysis.

Question 15

Which of the following best explains why enzymes are highly selective for their substrates?

Accepted Answer

The three-dimensional structure of the active site is complementary to the substrate.

Question 16

Which of the following is a characteristic of a multimeric enzyme?

Accepted Answer

It consists of more than one polypeptide chain.

Question 17

Which of the following best describes the effect of a non-competitive inhibitor on enzyme kinetics?

Accepted Answer

$V_{max}$ decreases, $K_m$ remains unchanged.

Question 18

Which of the following is a real-world example of enzyme inhibition used in medicine?

Accepted Answer

Penicillin inhibits bacterial transpeptidase, preventing cell wall synthesis.

Question 19

Which of the following statements about the classification of enzymes is correct?

Accepted Answer

Transferases catalyze the transfer of functional groups from one molecule to another.

Enzyme Structure, Classification, and Kinetics in Biochemistry

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