Question 1

Which of the following best describes a zwitterion at physiological pH?

Accepted Answer

An amino acid with a protonated amino group ($$\mathrm{NH_3$^+}) $$and a deprotonated carboxyl group ($$\mathrm{COO^-}).$$

Question 2

Which property is primarily responsible for the clustering of hydrophobic amino acids within the interior of proteins?

Accepted Answer

Hydrophobic effect

Question 3

Which of the following amino acids contains a thiol ($$\mathrm{-SH}) $$group in its side chain?

Accepted Answer

Cysteine

Question 4

Amino acids are classified as L or D based on the configuration around which carbon atom?

Accepted Answer

The alpha ($$\alpha) $$carbon

Question 5

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

Accepted Answer

Serine

Question 6

At a pH below the pKa of the carboxyl group, what is the predominant form of the carboxyl group in an amino acid?

Accepted Answer

$$\mathrm{COOH}$$

Question 7

Which of the following amino acids has a side chain that can form disulfide bonds?

Accepted Answer

Cysteine

Question 8

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

Accepted Answer

It is the pH at which the amino acid has no net electric charge.

Question 9

Which amino acid contains an imidazole group in its side chain, allowing it to act as a buffer near physiological pH?

Accepted Answer

Histidine

Question 10

A child suffering from kwashiorkor is most likely deficient in which of the following?

Accepted Answer

Essential amino acids

Question 11

Which of the following best describes the titration curve of glycine?

Accepted Answer

It has three inflection points, with the middle point representing the isoelectric point ($$pI).$$

Question 12

Which of the following amino acids is most likely to participate in acid-base catalysis due to its side chain pKa near physiological pH?

Accepted Answer

Histidine

Question 13

Which of the following statements about proline is correct?

Accepted Answer

Its side chain forms a ring with the amino group, restricting backbone flexibility.

Question 14

Which of the following amino acids is classified as a basic (positively charged) amino acid at physiological pH?

Accepted Answer

Lysine

Question 15

Which of the following best explains why proteins can be separated by isoelectric focusing?

Accepted Answer

Proteins migrate to the pH where they have no net charge.

Question 16

Which of the following amino acids contains a guanidinium group in its side chain?

Accepted Answer

Arginine

Question 17

Which of the following is a correct statement about the structure of all standard amino acids (except glycine)?

Accepted Answer

They have a chiral alpha carbon.

Question 18

Which of the following amino acids is most likely to be found in the active site of an enzyme that catalyzes proton transfer?

Accepted Answer

Histidine

Question 19

Which of the following amino acids has a side chain that can participate in hydrogen bonding but is uncharged at physiological pH?

Accepted Answer

Serine

Question 20

Which of the following best describes the difference between Fischer projections and stereochemical renderings?

Accepted Answer

Fischer projections are used to visualize constituent atoms, while stereochemical renderings are used to visualize molecular shape.

Amino Acids: Structure, Properties, and Biochemical Significance

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