Question 1

Which of the following best describes the amphipathic nature of biomolecules, and why is this property crucial for biological membranes?

Accepted Answer

Amphipathic molecules have both hydrophilic and hydrophobic regions, enabling the formation of bilayers in membranes.

Question 2

A solution contains a weak acid and its conjugate base. Using the Henderson-Hasselbalch equation, calculate the pH if $[A^-] = 0.1$ M, $[HA] = 0.01$ M, and $pK_a = 5.0$.

$	ext{pH} = pK_a + \log_{10}\left(\frac{[A^-]}{[HA]}ight)$

Accepted Answer

$	ext{pH} = 6.0$

Question 3

Which statement about the peptide bond in proteins is correct?

Accepted Answer

The peptide bond has partial double-bond character, restricting rotation.

Question 4

A patient’s blood pH is measured at 7.1. Which of the following best describes the condition and its biochemical implications?

Accepted Answer

The patient is experiencing acidosis, which can disrupt enzyme activity and protein structure.

Question 5

Which of the following is a correct statement about the secondary structure of proteins?

Accepted Answer

Secondary structure is stabilized by hydrogen bonds between backbone atoms.

Question 6

Which equation describes the initial velocity ($v_0$) of an enzyme-catalyzed reaction according to the Michaelis-Menten model?

Accepted Answer

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

Question 7

Which of the following best explains the role of chaperones in protein folding?

Accepted Answer

Chaperones prevent misfolding and aggregation by assisting correct folding pathways.

Question 8

A mutation causes a substitution of a hydrophobic amino acid for a hydrophilic one in the core of a globular protein. What is the most likely consequence?

Accepted Answer

The protein may misfold or lose stability due to disruption of the hydrophobic core.

Question 9

Which of the following statements about prions is correct?

Accepted Answer

Prions are infectious proteins that cause disease by inducing misfolding of normal proteins.

Question 10

Which of the following is an example of a fibrous protein, and what is its primary function?

Accepted Answer

Collagen; structural support in connective tissues

Question 11

Which of the following best describes the effect of a competitive inhibitor on enzyme kinetics?

Accepted Answer

It increases $K_m$ but does not affect $V_{max}$.

Question 12

Which of the following amino acids is most likely to participate in general acid-base catalysis in enzyme active sites?

Accepted Answer

Histidine

Question 13

A protein’s quaternary structure is disrupted by treatment with a reducing agent. Which type of interaction is most likely affected?

Accepted Answer

Disulfide bonds between cysteine residues

Question 14

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

Accepted Answer

Enzymes bring substrates into close proximity and correct orientation to facilitate reaction.

Question 15

Which of the following is true regarding the role of water as the medium of life?

Accepted Answer

Water’s polarity allows it to dissolve ionic and polar substances, facilitating biochemical reactions.

Question 16

Which of the following best explains the specificity of chymotrypsin for aromatic amino acids?

Accepted Answer

Chymotrypsin’s active site contains a hydrophobic pocket that accommodates aromatic side chains.

Question 17

Which of the following statements about zymogens is correct?

Accepted Answer

Zymogens are inactive enzyme precursors that are activated by proteolytic cleavage.

Question 18

A titration curve of a weak acid shows a buffer region. What is the significance of the buffer region in physiological systems?

Accepted Answer

It represents the pH range where the solution resists changes in pH upon addition of acid or base.

Question 19

Which of the following best describes the effect of phosphorylation on enzyme activity?

Accepted Answer

Phosphorylation can either activate or inactivate enzymes, depending on the context.

Biochemistry Study Guide: Biomolecules, Protein Structure, and Enzyme Mechanisms

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