Question 1

Which of the following best describes the primary structure of a protein?

Accepted Answer

The sequence of amino acids connected by peptide bonds in the polypeptide chain.

Question 2

Which of the following amino acids is achiral?

Accepted Answer

Glycine

Question 3

At physiological pH (7.4), which form does an amino acid most commonly exist in?

Accepted Answer

As a zwitterion with a positively charged –NH3+ group and a negatively charged –COO– group.

Question 4

Which type of interaction is primarily responsible for stabilizing the secondary structure of proteins?

Accepted Answer

Hydrogen bonds between backbone carbonyl and amide groups.

Question 5

Which of the following statements about peptide bonds is correct?

Accepted Answer

A peptide bond is an amide bond formed between the –COOH group of one amino acid and the –NH2 group of another.

Question 6

Which of the following amino acids would you expect to be most hydrophobic?

Accepted Answer

Phenylalanine

Question 7

A protein is denatured by heating. Which level(s) of protein structure are disrupted?

Accepted Answer

Secondary, tertiary, and quaternary structures.

Question 8

Which of the following best describes a conjugated protein?

Accepted Answer

A protein that contains a non–amino acid component essential for its function.

Question 9

Which of the following is a correct description of the quaternary structure of hemoglobin?

Accepted Answer

Four polypeptide chains, each with a heme group, held together by hydrophobic interactions.

Question 10

Which of the following agents can cause protein denaturation by disrupting salt bridges?

Accepted Answer

High concentrations of inorganic salts

Question 11

Which of the following best explains why proteins with nonpolar side chains tend to fold with these groups on the inside of the molecule?

Accepted Answer

Nonpolar side chains are hydrophobic and avoid contact with water.

Question 12

Which of the following is a real-life example of a fibrous protein and its function?

Accepted Answer

Collagen providing structure to tendons and cartilage.

Question 13

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

Accepted Answer

At the pI, the amino acid has equal numbers of positive and negative charges.

Question 14

Which of the following best describes the effect of a single amino acid substitution in the primary structure of a protein?

Accepted Answer

It can drastically alter the protein’s biological properties.

Question 15

Which of the following enzymes hydrolyzes peptide bonds on the carboxyl side of aromatic amino acids?

Accepted Answer

Chymotrypsin

Question 16

Which of the following interactions is responsible for forming a disulfide bond in a protein?

Accepted Answer

Covalent bonding between two cysteine side chains.

Question 17

A solution contains the dipeptide Ala-Gly. Which end of the peptide is the N-terminus?

Accepted Answer

The alanine end

Question 18

Which of the following best describes the difference between secondary and tertiary protein structure?

Accepted Answer

Secondary structure is stabilized by hydrogen bonds between backbone atoms, while tertiary structure is stabilized by interactions between side chains.

Question 19

Which of the following is a likely consequence of protein misfolding in the body?

Accepted Answer

The protein may lose its biological function.

Question 20

Which of the following best describes the effect of adding a strong acid to a solution of an amino acid at its isoelectric point?

Accepted Answer

The amino acid will gain a proton on the –COO– group, forming –COOH.

Amino Acids and Proteins: Structure, Properties, and Functions

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