Question 1

Which amino acid side chain is most likely to act as a general acid in an enzyme active site, given its ability to donate a proton at physiological pH?

Accepted Answer

Histidine ($$\mathrm{His})$$

Question 2

In covalent catalysis, which of the following best describes the movement of electrons during the attack of a nucleophile on an electrophile?

Accepted Answer

Electrons move from the nucleophile to the electrophile.

Question 3

Which of the following reactions is most likely to generate a carbocation intermediate in enzyme-catalyzed processes?

Accepted Answer

Heterolytic cleavage of a carbon-carbon bond

Question 4

Which of the following is a common strategy for stabilizing carbanion intermediates in enzyme active sites?

Accepted Answer

Formation of resonance structures with adjacent carbonyl groups

Question 5

Which amino acids are most likely to function as nucleophiles in covalent catalysis?

Accepted Answer

Cysteine ($$\mathrm{Cys}) $$and Serine ($$\mathrm{Ser})$$

Question 6

Which of the following best describes the difference between a racemase and an epimerase?

Accepted Answer

A racemase inverts the configuration at a single chiral center, while an epimerase inverts the configuration at one of several chiral centers.

Question 7

Which of the following is the most common type of intermediate in carbohydrate isomerase reactions?

Accepted Answer

Carbanion

Question 8

In a dehydration reaction catalyzed by enolase in glycolysis, which two chemical moieties are removed from the substrate?

Accepted Answer

A proton and a hydroxyl group

Question 9

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

Accepted Answer

The local environment can stabilize or destabilize the charged form.

Question 10

Which of the following is a common feature of charge delocalization mechanisms that stabilize carbanions?

Accepted Answer

Proximity to a more electronegative atom, such as oxygen or nitrogen

Question 11

Which of the following is the correct product of a dehydration reaction that eliminates a proton and a hydroxyl group from adjacent carbons?

Accepted Answer

A carbon-carbon double bond

Question 12

Which of the following is the most common electron acceptor in carbohydrate catabolism involving hydride transfer?

Accepted Answer

$$\mathrm{NAD^+}$$

Question 13

Which of the following is true about the two-electron redox chemistry of hydride transfer?

Accepted Answer

A hydride contains two electrons and one proton.

Question 14

Which of the following is an example of an electrophilic center in enzyme-catalyzed reactions?

Accepted Answer

Carbony carbon

Question 15

Which of the following amino acids is most likely to act as a general base in an enzyme active site?

Accepted Answer

Glutamate ($$\mathrm{Glu})$$

Question 16

Which of the following best describes the role of a mutase in carbohydrate metabolism?

Accepted Answer

It catalyzes the intramolecular shift of a chemical group within a substrate.

Question 17

Which of the following is a common nucleophile in enzyme reactions?

Accepted Answer

Primary amine

Question 18

Which of the following is a plausible mechanism for stabilizing a carbanion intermediate in an enzyme active site?

Accepted Answer

Resonance stabilization with an adjacent carbonyl group

Question 19

Which of the following statements about S$$_N2 $$reactions in biochemistry is correct?

Accepted Answer

S$$_N2 $$reactions with tetrahedral intermediates are common in biochemistry.

Biochemical Catalysis, Enzyme Mechanisms, and Carbon Intermediates: Study Notes

Study Guide - Practice Questions

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