Question 1

Which of the following best describes the primary function of enzymes in biological systems?

Accepted Answer

Enzymes lower the activation energy ($$\Delta G$$^{\ddagger}$$) required for a reaction.

Question 2

The oxidation of glucose is highly exergonic, as shown by the equation:

$$\mathrm{C_6H_{12}O_6$ + 6\ O_2$ \rightarrow 6\ CO_2$ + 6\ H_2O + 2870\ kJ}$$

Why does glucose not spontaneously combust in your coffee cup?

Accepted Answer

The activation energy ($$\Delta G$$^{\ddagger}$$) is too high without a catalyst.

Question 3

Which of the following statements about enzyme specificity is correct?

Accepted Answer

Enzymes achieve specificity through complementarity with their substrates.

Question 4

A scientist is studying an enzyme that catalyzes the reaction:

$$\mathrm{ATP + D	ext{-}glucose ightarrow ADP + D	ext{-}glucose	ext{-}6	ext{-}phosphate}$$

According to the Enzyme Commission (E.C.) classification, what is the correct class for this enzyme?

Accepted Answer

Transferase (Class 2)

Question 5

Which of the following is NOT a way cells can regulate enzyme activity?

Accepted Answer

Changing the atomic number of the protein

Question 6

Which of the following best explains why enzymes are not considered to be consumed in a reaction?

Accepted Answer

Enzymes are regenerated at the end of each catalytic cycle.

Question 7

A researcher finds that an enzyme-catalyzed reaction has a $$V_{max} of$$ $$3 	imes 10^4$ s$$^{-1}$$ and an uncatalyzed rate of 3$$ 	imes $$10^{-10} s$^{-1}. $$What is the catalytic power of this enzyme?

Accepted Answer

$$10^{14}$$

Question 8

Which of the following is a common role of cofactors in enzyme catalysis?

Accepted Answer

They assist in catalysis, often by stabilizing charges or transferring groups.

Question 9

Which of the following statements about enzyme-catalyzed reactions is FALSE?

Accepted Answer

Enzymes can make a thermodynamically unfavorable reaction proceed spontaneously.

Question 10

Which of the following best describes the role of the active site of an enzyme?

Accepted Answer

It creates an environment that facilitates the conversion of substrate to product.

Question 11

A patient is found to have a deficiency in a coenzyme required for a metabolic pathway. Which of the following is the most likely consequence?

Accepted Answer

The pathway will be slowed or blocked due to impaired enzyme function.

Question 12

Which of the following is the correct equation for the free energy of activation?

Accepted Answer

$$\Delta G$$^{\ddagger}$$ = G_{transition\ state} - G_{reactants}$$

Question 13

Which of the following is a real-world example of an enzyme-catalyzed reaction that is essential for life?

Accepted Answer

The conversion of citrate to isocitrate by aconitase in the citric acid cycle.

Question 14

Which of the following best explains why controlling enzyme activity is more efficient for cells than controlling strictly chemical reactions?

Accepted Answer

Enzyme activity can be regulated by multiple mechanisms, allowing rapid and reversible control.

Question 15

Which of the following is the best definition of 'flux' in a metabolic pathway?

Accepted Answer

The total amount of initial substrate converted to final product over time.

Question 16

A mutation in the active site of an enzyme reduces its ability to stabilize the transition state. What is the most likely effect on the reaction?

Accepted Answer

The activation energy ($$\Delta G$$^{\ddagger}$$) will increase, and the reaction rate will decrease.

Question 17

Which of the following is an example of a regulatory or rate-determining enzyme in a metabolic pathway?

Accepted Answer

Hexokinase in glycolysis

Question 18

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

Accepted Answer

Enzymes do not affect the equilibrium position; they only affect the rate at which equilibrium is reached.

Enzymes: Catalysis and Kinetics – Structure, Function, and Regulation

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