Question 1

Which of the following best describes how an enzyme increases the rate of a chemical reaction?

Accepted Answer

By stabilizing the transition state and lowering the activation energy ($$E_a)$$

Question 2

According to the induced fit model of enzyme catalysis, what happens when a substrate binds to an enzyme?

Accepted Answer

The enzyme changes conformation to better fit and stabilize the transition state

Question 3

Which amino acid is most likely to act as a general base in enzyme catalysis at physiological pH, based on its pKa?

Accepted Answer

Histidine (pKa ~6-7)

Question 4

A competitive inhibitor affects enzyme kinetics by:

Accepted Answer

Increasing $$K_M$$ but leaving $$V_{max}$$ unchanged

Question 5

Which of the following is true about the catalytic triad in serine proteases?

Accepted Answer

It consists of Serine, Histidine, and Aspartate, which work together to activate the serine for nucleophilic attack

Question 6

Which of the following statements about $$K_M in $$the Michaelis-Menten equation is correct?

Accepted Answer

$$K_M is $$the substrate concentration at which the reaction rate is half-maximal

Question 7

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

Accepted Answer

Enzymes bind substrates through multiple weak interactions that are optimized for the transition state

Question 8

Which of the following is a property of a noncompetitive (mixed) inhibitor?

Accepted Answer

It decreases $$V_{max}$$ but may or may not change $$K_M$$

Question 9

Which of the following best describes the effect of pH on enzyme activity?

Accepted Answer

Changes in pH can alter the ionization state of amino acid side chains in the active site, affecting catalysis

Question 10

Which of the following is a correct statement about the role of metal ions in enzyme catalysis?

Accepted Answer

Metal ions can stabilize negative charges and assist in substrate binding

Question 11

Which of the following best describes the difference between the lock-and-key and induced-fit models of enzyme-substrate interaction?

Accepted Answer

The lock-and-key model proposes a rigid active site, while the induced-fit model involves conformational changes in the enzyme upon substrate binding

Question 12

Which of the following is true about uncompetitive inhibition?

Accepted Answer

Both $$K_M$$ and $$V_{max}$$ decrease by the same factor

Question 13

Which of the following is a real-world example of feedback inhibition in metabolic pathways?

Accepted Answer

The final product of a pathway inhibits the first enzyme in the pathway

Question 14

Which of the following best describes the role of the oxyanion hole in serine proteases?

Accepted Answer

It stabilizes the negative charge on the tetrahedral intermediate during peptide bond cleavage

Question 15

Which of the following is the correct Michaelis-Menten equation for initial velocity ($$v) as a $$function of substrate concentration ($$[S]$$)?

Accepted Answer

$$v = \frac{V_{max} [S]}{K_M + [S]}$$

Question 16

Which of the following statements about the specificity constant ($$\frac{k_{cat}}{K_M}) is $$correct?

Accepted Answer

It measures the catalytic efficiency of an enzyme at low substrate concentrations

Question 17

Which of the following is a property of mechanism-based (suicide) inhibitors?

Accepted Answer

They are activated by the enzyme and form a covalent bond, irreversibly inactivating the enzyme

Question 18

Which of the following amino acids is most likely to participate in covalent catalysis in enzyme active sites?

Accepted Answer

Cysteine

Question 19

Which of the following best explains why the pKa of an amino acid side chain can be significantly shifted in an enzyme active site?

Accepted Answer

The presence of nearby charged or polar groups can stabilize or destabilize the ionized form

Enzyme Catalysis, Mechanisms, and Carbohydrate Structure: Mini-Textbook Study Notes

Study Guide - Practice Questions