Question 1

Which of the following amino acids is classified as aromatic and nonpolar?

Accepted Answer

Phenylalanine

Question 2

A patient presents with metabolic acidosis. Which amino acid would most likely buffer the excess protons due to its side chain pKa near physiological pH?

Accepted Answer

Histidine

Question 3

Which equation would you use to calculate the pH of a solution containing a weak acid and its conjugate base?

Accepted Answer

$$\mathrm{pH} = \mathrm{p}K_a + \log_{10}\left(\frac{[\mathrm{A}^-]}{[\mathrm{HA}]}\right)$$

Question 4

Which of the following amino acids would most likely be found on the exterior of a soluble protein in aqueous solution?

Accepted Answer

Glutamine

Question 5

A peptide contains the sequence: Ala-Glu-Lys-Tyr. Which residue contributes a positive charge at pH 7?

Accepted Answer

Lysine

Question 6

If the concentration of a weak acid ($$[\mathrm{HA}]) is 0.1 M $$and its conjugate base ($$[\mathrm{A}^-]) is 0.01 M$$, and $$\mathrm{p}K_a = 5.0$$, what is the pH of the solution?

Accepted Answer

$$4.0$$

Question 7

Which amino acid contains a thiol group and can form disulfide bonds in proteins?

Accepted Answer

Cysteine

Question 8

Which of the following is a correct statement about the isoelectric point ($$pI) of an $$amino acid?

Accepted Answer

It is the pH at which the amino acid is least soluble in water.

Question 9

Which amino acid would you expect to be most abundant in the transmembrane region of an integral membrane protein?

Accepted Answer

Leucine

Question 10

A solution contains 0.05 M acetic acid ($$\mathrm{p}K_a = 4.76) $$and 0.05 M sodium acetate. What is the pH of the solution?

Accepted Answer

$$4.76$$

Question 11

Which amino acid is most likely to participate in hydrogen bonding due to its side chain?

Accepted Answer

Serine

Question 12

Which of the following amino acids is polar and uncharged at physiological pH?

Accepted Answer

Glutamine

Question 13

A protein is denatured by heating. Which type of bond is most likely to be disrupted first?

Accepted Answer

Hydrogen bonds

Question 14

Which amino acid has a side chain that can act as a nucleophile in enzyme catalysis?

Accepted Answer

Serine

Question 15

Which of the following best describes the structure of glycine?

Accepted Answer

It is the only amino acid without a chiral center.

Question 16

Which amino acid is most likely to be phosphorylated during signal transduction?

Accepted Answer

Serine

Question 17

A solution contains 0.1 M of a weak acid and 0.1 M of its conjugate base. If $$\mathrm{p}K_a = 6.0$$, what is the pH?

Accepted Answer

$$6.0$$

Question 18

Which amino acid is most likely to form salt bridges in proteins due to its charged side chain?

Accepted Answer

Glutamate

Question 19

Which of the following amino acids is most likely to be found in the active site of an enzyme that catalyzes acid-base reactions?

Accepted Answer

Histidine

Question 20

Which amino acid is most likely to disrupt an alpha helix due to its rigid cyclic structure?

Accepted Answer

Proline

Biochemistry Study Guide: Amino Acids and Problem Set Overview

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