Question 1

Which of the following best describes why enzymes are more effective than chemical catalysts under physiological conditions?

Accepted Answer

Enzymes function efficiently under physiological temperature and pH, and exhibit high specificity and regulation.

Question 2

Which statement about the effect of enzymes on reaction equilibrium is correct?

Accepted Answer

Enzymes do not affect the equilibrium position; they only speed up the attainment of equilibrium.

Question 3

A reaction has a negative $$\Delta G. $$What does this indicate about the reaction?

Accepted Answer

The reaction is spontaneous and can proceed without input of energy.

Question 4

Which of the following is a key feature of the active site of an enzyme?

Accepted Answer

It is a flexible 3D cleft that binds substrates via multiple weak interactions.

Question 5

Which of the following is NOT a way substrate binding promotes catalysis?

Accepted Answer

Increasing the activation energy required for the reaction.

Question 6

The Michaelis-Menten equation is given by $$Vo = \frac{V_{max}[S]}{K_m + [S]}. $$What is the initial velocity ($$Vo) $$when $$[S] = K_m$$?

Accepted Answer

$$Vo = \frac{V_{max}}{2}$$

Question 7

Which type of reversible enzyme inhibition can be overcome by increasing substrate concentration?

Accepted Answer

Competitive inhibition

Question 8

A Lineweaver-Burk plot is a double reciprocal plot of $$1/Vo$$ versus $$1/[S]. $$What does the y-intercept represent?

Accepted Answer

$$1/V_{max}$$

Question 9

Which of the following best describes the catalytic triad in serine proteases?

Accepted Answer

It is composed of Asp, His, and Ser, which work together to activate the serine for nucleophilic attack.

Question 10

Which statement about allosteric enzymes is TRUE?

Accepted Answer

They are often regulated by non-covalent binding of modulators at sites other than the active site.

Question 11

Which of the following is a real-life example of competitive inhibition?

Accepted Answer

Sulfa drugs inhibiting bacterial folate synthesis by mimicking PABA

Question 12

Which of the following is TRUE regarding the effect of noncompetitive inhibitors on enzyme kinetics?

Accepted Answer

They decrease $$V_{max}$$ without affecting $$K_m.$$

Question 13

Which of the following is a common mechanism for short-term regulation of enzyme activity?

Accepted Answer

Covalent modification such as phosphorylation

Question 14

Which of the following statements about the Circe effect is correct?

Accepted Answer

It describes enzymes that attract and bind substrates so efficiently that catalysis is limited only by diffusion.

Question 15

Which of the following is a direct consequence of substrate binding in the active site?

Accepted Answer

Distortion of the substrate to resemble the transition state

Question 16

Which of the following best describes the role of histidine in the catalytic triad of serine proteases?

Accepted Answer

It acts as a general acid and base, facilitating proton transfer during catalysis.

Question 17

Which of the following is the correct formula for enzyme turnover number ($$k_{cat}$$)?

Accepted Answer

$$k_{cat} = \frac{V_{max}}{[E_t]}$$

Question 18

Which of the following is a physiological example of enzyme regulation by covalent modification?

Accepted Answer

Activation of glycogen phosphorylase by phosphorylation during fasting or stress

Question 19

Which of the following statements about allosteric enzymes is FALSE?

Accepted Answer

They are always activated by their end products.

Module 6: Enzymes – Structure, Function, and Kinetics

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