Question 1

Which of the following statements best describes the role of the transition state in enzyme-catalyzed reactions?

Accepted Answer

Enzymes stabilize the transition state, lowering the activation energy required for the reaction.

Question 2

A Michaelis-Menten plot of initial velocity ($$v_0) $$versus substrate concentration ($$[S]) $$for an enzyme-catalyzed reaction is hyperbolic. What does the substrate concentration at which $$v_0$$ = \frac{1}{2}V_{max}$$ represent?

Accepted Answer

The Michaelis constant, $$K_m$$

Question 3

Which of the following best describes the difference between competitive and noncompetitive inhibition as observed in a Lineweaver-Burk plot?

Accepted Answer

Competitive inhibition increases the apparent $$K_m$$ but does not affect $$V_{max}$$, while noncompetitive inhibition decreases $$V_{max}$$ but does not change $$K_m.$$

Question 4

A patient is given a drug that acts as a mechanism-based inhibitor of an enzyme. Which property distinguishes this inhibitor from other types?

Accepted Answer

It forms a covalent bond with the enzyme during the normal catalytic process, irreversibly inactivating it.

Question 5

Which of the following equations correctly represents the Michaelis-Menten equation for a single substrate enzyme-catalyzed reaction?

Accepted Answer

$$v_0$$ = \frac{V_{max}[S]}{K_m + [S]}$$

Question 6

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

Accepted Answer

It consists of serine, histidine, and aspartate residues that work together to facilitate peptide bond hydrolysis.

Question 7

Which of the following best describes the difference between aldoses and ketoses?

Accepted Answer

Aldoses contain an aldehyde group at carbon 1, while ketoses contain a ketone group typically at carbon 2.

Question 8

Which of the following statements about the formation of a glycosidic bond in disaccharides is correct?

Accepted Answer

A glycosidic bond forms when the anomeric carbon of one monosaccharide reacts with a hydroxyl group of another.

Question 9

Which of the following best describes the difference between O-linked and N-linked glycoproteins?

Accepted Answer

O-linked glycoproteins have carbohydrates attached to the hydroxyl group of serine or threonine, while N-linked glycoproteins have carbohydrates attached to the amide nitrogen of asparagine.

Question 10

A patient with type O blood can safely receive blood from which of the following donors?

Accepted Answer

Type O only

Question 11

Which of the following best describes the difference between nucleosides and nucleotides?

Accepted Answer

Nucleotides contain a phosphate group, while nucleosides do not.

Question 12

Which of the following correctly represents the direction in which nucleotides are added to a growing polynucleotide chain during DNA synthesis?

Accepted Answer

5' to 3' direction

Question 13

Which of the following is a correct statement about the Watson-Crick base pairs in DNA?

Accepted Answer

Adenine pairs with thymine via two hydrogen bonds, and guanine pairs with cytosine via three hydrogen bonds.

Question 14

Which of the following best describes the role of ATP as a cofactor in group transfer reactions?

Accepted Answer

ATP donates a phosphoryl group to substrates, facilitating group transfer reactions.

Question 15

Which of the following is a distinguishing feature of FAD/FADH$$_2$$ compared to NAD$$^+/$$NADH as a cofactor in redox reactions?

Accepted Answer

FAD can accept two electrons and two protons, often forming a covalent bond with the enzyme, while NAD$$^+$$ typically accepts two electrons and one proton and is freely diffusible.

Question 16

A researcher is studying an enzyme that shows sigmoidal kinetics in a Michaelis-Menten plot. Which of the following is the most likely explanation for this observation?

Accepted Answer

The enzyme is allosteric and exhibits cooperative substrate binding.

Question 17

Which of the following best describes the proximity effect in enzyme catalysis?

Accepted Answer

Enzymes bring substrates into close proximity and correct orientation to increase the rate of reaction.

Question 18

Which of the following statements about the cyclization of monosaccharides is correct?

Accepted Answer

Cyclization creates a new chiral center at the anomeric carbon, resulting in alpha and beta anomers.

Question 19

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

Accepted Answer

The lock-and-key model suggests the active site is rigid and complementary to the substrate, while the induced-fit model proposes the active site changes shape upon substrate binding.

BCH 351 Exam 2 Study Guide: Enzymes, Carbohydrates, and Nucleic Acids

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