Question 1

Which of the following best describes the role of enzymes in biological reactions?

Accepted Answer

Enzymes stabilize the transition state, thereby lowering the activation energy.

Question 2

Given the Michaelis-Menten equation $$v = \frac{V_{max}[S]}{K_m + [S]}$$, which statement is TRUE regarding the kinetic parameters?

Accepted Answer

$$V_{max} is $$the rate when the enzyme is saturated with substrate.

Question 3

A Lineweaver-Burk plot of an enzyme reaction shows lines intersecting at the y-axis. What type of inhibition is most likely present?

Accepted Answer

Competitive inhibition

Question 4

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

Accepted Answer

Lock-and-key model suggests the enzyme active site is rigid and complementary to the substrate, while induced-fit model suggests the enzyme changes shape to accommodate the substrate.

Question 5

Which kinetic parameter is defined as the turnover number, representing the number of substrate molecules converted to product per enzyme molecule per second?

Accepted Answer

$$k_{cat}$$

Question 6

A patient is given a mechanism-based inhibitor for an enzyme. Which feature distinguishes this inhibitor from competitive and noncompetitive inhibitors?

Accepted Answer

It forms a covalent bond with the enzyme during catalysis, permanently inactivating it.

Question 7

Which of the following statements about cofactors is CORRECT?

Accepted Answer

Coenzymes are organic molecules that assist enzymes, and can be either cosubstrates or prosthetic groups.

Question 8

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

Accepted Answer

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

Question 9

Which term describes monosaccharides that differ only at a single chiral center?

Accepted Answer

Epimers

Question 10

During the cyclization of glucose, which carbon becomes the new chiral center (anomeric carbon)?

Accepted Answer

Carbon 1

Question 11

Which of the following best describes a reducing sugar?

Accepted Answer

A sugar with a free anomeric carbon capable of acting as a reducing agent.

Question 12

Which statement about glycoproteins is TRUE?

Accepted Answer

O-linked glycoproteins are attached to the oxygen atom of serine or threonine residues.

Question 13

Which of the following is a correct description of the structure of a nucleotide?

Accepted Answer

A nucleotide consists of a nucleobase, a ribose or deoxyribose sugar, and a phosphate group.

Question 14

Which linkage connects nucleotides in DNA and RNA chains?

Accepted Answer

Phosphodiester bond

Question 15

Which of the following statements about Watson-Crick base pairing is CORRECT?

Accepted Answer

G pairs with C via three hydrogen bonds.

Question 16

Which of the following is a function of ATP as a cofactor?

Accepted Answer

ATP provides energy and acts as a group transfer cofactor.

Question 17

A patient with blood type O can donate blood to which of the following recipients?

Accepted Answer

To all blood types (A, B, AB, O).

Question 18

Which of the following best describes the role of NAD(P)+ in biochemical reactions?

Accepted Answer

NAD(P)+ acts as an electron acceptor in redox reactions.

Question 19

Which of the following statements about RNA is CORRECT?

Accepted Answer

RNA contains uracil instead of thymine.

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

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