Question 1

Which of the following best explains why enzymes are preferred over inorganic catalysts in biological systems?

Accepted Answer

Enzymes provide greater reaction specificity, milder reaction conditions, higher reaction rates, and regulatory capacity.

Question 2

Which statement about the 'induced fit' model of enzyme-substrate interaction is CORRECT?

Accepted Answer

Both the enzyme and substrate can undergo conformational changes to achieve optimal binding.

Question 3

Which of the following is a key feature of the transition state theory as it applies to enzyme catalysis?

Accepted Answer

Enzymes stabilize the transition state, lowering the activation energy ($$\Delta G$$^{\ddagger}$$).

Question 4

Which amino acid is most likely to act as a general acid or base in enzyme catalysis due to its side chain pKa near physiological pH?

Accepted Answer

Histidine

Question 5

A mutation in the active site of lysozyme replaces Glu35 with Gln. What is the most likely effect on catalysis?

Accepted Answer

Catalysis is impaired because Gln cannot donate a proton like Glu.

Question 6

Which of the following equations represents the Michaelis-Menten equation for enzyme kinetics?

Accepted Answer

$$V = V_{max} \dfrac{[S]}{K_m + [S]}$$

Question 7

If an enzyme has a $$K_m of 0.5 mM$$, what substrate concentration $$[S] is $$required to achieve 90% of $$V_{max}$$?

Accepted Answer

$$[S] = 4.5 mM$$

Question 8

Which of the following statements about competitive inhibition is TRUE?

Accepted Answer

Competitive inhibitors bind to the active site and increase the apparent $$K_m$$ without affecting $$V_{max}.$$

Question 9

Which type of enzyme inhibition is characterized by a decrease in $$V_{max}$$ with no change in $$K_m$$?

Accepted Answer

Non-competitive inhibition

Question 10

Which of the following best describes the role of metal ions in enzyme catalysis?

Accepted Answer

They stabilize negative charges and can participate in redox reactions.

Question 11

A patient is given a drug that acts as an irreversible inhibitor of an essential enzyme. What is the most likely outcome?

Accepted Answer

The enzyme will be permanently inactivated and new enzyme must be synthesized.

Question 12

Which of the following is NOT a reason why enzymes are highly specific for their substrates?

Accepted Answer

Enzymes bind all substrates equally well.

Question 13

Which of the following best describes the effect of an allosteric activator on an enzyme?

Accepted Answer

It binds to a regulatory site and increases enzyme activity.

Question 14

Which of the following is a correct statement about the Lineweaver-Burk plot?

Accepted Answer

The y-intercept equals $$1/V_{max}.$$

Question 15

Which of the following mechanisms is used by lysozyme to cleave peptidoglycan?

Accepted Answer

Both acid/base and covalent catalysis

Question 16

During a purification procedure, an enzyme solution has an activity of 2 Units in 4 mg of protein. What is the specific activity?

Accepted Answer

0.5 Units/mg

Question 17

Which of the following is a real-life example of metal ion catalysis in biology?

Accepted Answer

Electron transport chain in mitochondria

Question 18

Which of the following statements about enzyme kinetics is FALSE?

Accepted Answer

Increasing substrate concentration always increases reaction velocity linearly.

Question 19

Which of the following is a characteristic of covalent catalysis?

Accepted Answer

The enzyme forms a transient covalent bond with the substrate.

Enzymes: Structure, Function, Mechanisms, and Kinetics

Study Guide - Practice Questions