Question 1

Which of the following statements best explains why proteins such as collagen and keratin are classified as structural proteins?

Accepted Answer

They impart strength to biological structures such as bones, tendons, and hair.

Question 2

Which of the following amino acids contains a sulfur atom in its side chain?

Accepted Answer

Methionine

Question 3

Amino acids are linked together in proteins by which type of bond?

Accepted Answer

Amide bond

Question 4

Which of the following best describes the isoelectric point (pI) of an amino acid?

Accepted Answer

The pH at which the amino acid has no net charge.

Question 5

Which amino acid is most likely to migrate toward the cathode during electrophoresis at pH 6.0?

Accepted Answer

Arginine (pI = 10.76)

Question 6

Which of the following is an essential amino acid for humans?

Accepted Answer

Leucine

Question 7

Which method separates amino acids based on their polarity?

Accepted Answer

Chromatography

Question 8

What is the overall yield of a peptide containing 5 amino acids if each peptide bond formation has an 80% yield?

Accepted Answer

$$0.8^4 = 41$$\%$$

Question 9

Which reagent is used to selectively remove the N-terminal amino acid from a peptide during sequencing?

Accepted Answer

Edman’s reagent

Question 10

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

Accepted Answer

Cysteine

Question 11

Which enzyme cleaves peptide bonds on the C-terminal side of aromatic amino acids such as phenylalanine, tyrosine, and tryptophan?

Accepted Answer

Chymotrypsin

Question 12

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

Accepted Answer

The local folding of the polypeptide chain into alpha-helices and beta-sheets

Question 13

Which of the following conditions will most likely denature a protein?

Accepted Answer

Changing the pH of the solution

Question 14

Which of the following statements about peptide bonds is correct?

Accepted Answer

Peptide bonds have partial double bond character, restricting rotation.

Question 15

Which of the following best explains why the amino acid histidine is important in enzyme active sites?

Accepted Answer

Its side chain can act as both a proton donor and acceptor near physiological pH.

Question 16

Which of the following is a correct statement about the Strecker synthesis of amino acids?

Accepted Answer

It involves the reaction of an aldehyde with ammonia and cyanide, followed by hydrolysis.

Question 17

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

Accepted Answer

The arrangement of multiple polypeptide chains (subunits) in a single protein

Question 18

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

Accepted Answer

Histidine

Question 19

Which of the following statements about the separation of amino acids by ion-exchange chromatography is correct?

Accepted Answer

Amino acids are separated based on their net charge at a given pH.

Amino Acids, Peptides, and Proteins: Structure, Properties, and Synthesis

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