Question 1

Which of the following best describes a hydrogen bond in a biological system?

Accepted Answer

An electrostatic attraction between a hydrogen atom covalently bonded to an electronegative atom and another electronegative atom.

Question 2

Which equation correctly represents the Henderson-Hasselbalch equation for a weak acid?

Accepted Answer

$$\mathrm{pH} = \mathrm{p}K_a + \log \left( \frac{[A^-]}{[HA]} \right)$$

Question 3

A solution contains 0.1 M acetic acid ($$\mathrm{p}K_a = 4.75) $$and 0.1 M sodium acetate. What is the pH of the solution?

Accepted Answer

4.75

Question 4

Which of the following amino acids has a side chain that is positively charged at physiological pH?

Accepted Answer

Lysine

Question 5

Which type of noncovalent interaction is primarily responsible for the stabilization of the DNA double helix through base stacking?

Accepted Answer

$$\pi-$$stacking interactions

Question 6

Given the following reaction: $$\mathrm{HBr} + \mathrm{H_2O} \rightleftharpoons \mathrm{Br^-} + \mathrm{H_3O^+}$$, which species acts as the Brønsted-Lowry acid?

Accepted Answer

$$\mathrm{HBr}$$

Question 7

Which of the following statements about the relationship between $$K_a$$ and $$pK_a is $$correct?

Accepted Answer

$$pK_a = -\log K_a$$

Question 8

Which amino acid contains a sulfur atom in its side chain and is nonpolar?

Accepted Answer

Methionine

Question 9

A protein is placed in a solution at pH 2.0. Which amino acid side chain is most likely to be positively charged under these conditions?

Accepted Answer

Arginine

Question 10

Which of the following best describes a Lewis acid?

Accepted Answer

A substance that accepts an electron pair.

Question 11

Which of the following interactions is NOT classified as a hydrophobic interaction?

Accepted Answer

Electrostatic attraction between oppositely charged ions.

Question 12

If the equilibrium constant $$K$$ for a reaction is less than 1, which of the following statements is true?

Accepted Answer

The reaction favors the formation of reactants.

Question 13

Which of the following amino acids has a side chain with a $$pK_a$$ closest to physiological pH (7.4), making it important in enzyme active sites for proton transfer?

Accepted Answer

Histidine

Question 14

Which of the following is true regarding the spontaneity of a reaction and the sign of $$\Delta G$$?

Accepted Answer

A reaction with $$\Delta G \u003c 0 is $$spontaneous.

Question 15

Which of the following best explains why nonpolar amino acids tend to be found in the interior of globular proteins?

Accepted Answer

They are repelled by the aqueous environment, leading to hydrophobic interactions.

Question 16

Which of the following is a correct statement about the rate and thermodynamics of a chemical reaction?

Accepted Answer

The rate of a reaction is independent of its $$\Delta G$$ value.

Question 17

Which of the following amino acids contains an aromatic ring in its side chain?

Accepted Answer

Phenylalanine

Question 18

A patient is experiencing metabolic acidosis. Which amino acid side chain could act as a buffer in blood due to its $$pK_a$$ value being close to physiological pH?

Accepted Answer

Histidine

Question 19

Which of the following best describes the effect of increasing the concentration of a weak acid and its conjugate base in a buffer solution?

Accepted Answer

The buffer capacity increases.

Question 20

Which of the following is a correct application of the Brønsted-Lowry definition of acids and bases?

Accepted Answer

An acid is a proton donor and a base is a proton acceptor.

Biochemical Principles: Molecular Forces, Acids & Bases, and Amino Acids

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