Question 1

Which of the following elements is NOT commonly found in all proteins?

Accepted Answer

Phosphorus

Question 2

Amino acids are classified based on the properties of their R group. Which of the following amino acids is considered non-polar?

Accepted Answer

Leucine

Question 3

At physiological pH, which statement best describes the side chain of a polar acidic amino acid?

Accepted Answer

It bears a negative charge because the side chain carboxyl group has lost its acidic hydrogen atom.

Question 4

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

Accepted Answer

Methionine

Question 5

Which of the following is TRUE about essential amino acids?

Accepted Answer

They must be obtained from the diet because the body cannot synthesize them.

Question 6

Which amino acid is classified as basic and contains an imidazole ring in its side chain?

Accepted Answer

Histidine

Question 7

Which of the following best describes the structure of a peptide bond?

Accepted Answer

A bond formed between the carboxyl group of one amino acid and the amino group of another, releasing water.

Question 8

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

Accepted Answer

Serine

Question 9

Given the following peptide sequence: Ala-Gly-Ser, which of the following is the correct one-letter code representation?

Accepted Answer

AGS

Question 10

Which level of protein structure is primarily determined by the sequence of amino acids?

Accepted Answer

Primary structure

Question 11

Which of the following statements about non-polar amino acids is CORRECT?

Accepted Answer

They are hydrophobic and not attracted to water molecules.

Question 12

Which amino acid is considered a borderline member of the non-polar group due to its indole ring?

Accepted Answer

Tryptophan

Question 13

At physiological pH, which of the following amino acids would have a positively charged side chain?

Accepted Answer

Lysine

Question 14

Which of the following is a polar neutral amino acid that contains a thiol group?

Accepted Answer

Cysteine

Question 15

A mutation changes a glutamic acid residue to a valine residue in a protein. Which property of the protein is most likely to be affected?

Accepted Answer

Its overall charge at physiological pH

Question 16

Which of the following equations correctly represents the formation of a peptide bond between two amino acids?

Accepted Answer

$$\mathrm{Amino\ acid}_1 + \mathrm{Amino\ acid}_2 \rightarrow \mathrm{Dipeptide} + H_2O$$

Question 17

Which of the following amino acids is NOT essential in the human diet?

Accepted Answer

Glutamine

Question 18

Which property distinguishes polar neutral amino acids from polar acidic and basic amino acids?

Accepted Answer

Their side chains are uncharged but can form hydrogen bonds with water.

Question 19

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

Accepted Answer

The arrangement and interaction of multiple polypeptide chains in a protein complex.

Question 20

Which amino acid is most likely to form a disulfide bond, contributing to protein tertiary structure?

Accepted Answer

Cysteine

Proteins: Structure and Functions – Study Notes

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