Question 1

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

Accepted Answer

The specific linear sequence of amino acids in a polypeptide chain, written from the N-terminus to the C-terminus.

Question 2

Which amino acid is NOT classified as essential for humans?

Accepted Answer

Glutamine

Question 3

At physiological pH, which form do most amino acids exist in?

Accepted Answer

As a zwitterion with a positively charged amino group and a negatively charged carboxyl group

Question 4

Which of the following best explains why only L-amino acids are found in proteins synthesized by living organisms?

Accepted Answer

Enzymes responsible for protein synthesis are stereospecific and only recognize L-amino acids.

Question 5

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

Accepted Answer

Methionine

Question 6

A patient with sickle cell anemia has a mutation in the β-chain of hemoglobin. Which amino acid substitution is responsible for this disease?

Accepted Answer

Glutamic acid is replaced by valine at position 6

Question 7

Which of the following forces is primarily responsible for the stabilization of the tertiary structure of globular proteins in aqueous environments?

Accepted Answer

Hydrophobic interactions

Question 8

Which of the following best describes the chemical reaction that forms a peptide bond?

Accepted Answer

A condensation (dehydration) reaction between the α-carboxyl group of one amino acid and the α-amino group of another, releasing water

Question 9

Which of the following is a consequence of protein denaturation?

Accepted Answer

The protein loses its biological activity due to loss of secondary, tertiary, and quaternary structure

Question 10

Which of the following equations correctly represents the calculation of the isoelectric point ($$pI) $$for a simple amino acid with two ionizable groups?

Accepted Answer

$$pI = \frac{pK_{a1} + pK_{a2}}{2}$$

Question 11

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

Accepted Answer

Glutamate

Question 12

Which of the following statements about collagen is TRUE?

Accepted Answer

Collagen's quaternary structure consists of three left-handed α-chains twisted into a right-handed triple helix.

Question 13

Which of the following best describes the role of chaperone proteins in cells?

Accepted Answer

They provide a protective environment to assist in the correct folding of newly synthesized or partially denatured proteins.

Question 14

Which of the following amino acids is a precursor for the neurotransmitter serotonin?

Accepted Answer

Tryptophan

Question 15

Which of the following statements about the peptide bond is FALSE?

Accepted Answer

It is a nonpolar covalent bond with free rotation around the C–N axis.

Question 16

Which of the following is a function of proteins in the human body?

Accepted Answer

Acting as biocatalysts to speed up biochemical reactions

Question 17

Which of the following amino acids is most likely to disrupt an α-helix when present in the middle of the helix?

Accepted Answer

Proline

Question 18

Which of the following best describes the difference between parallel and antiparallel β-sheets?

Accepted Answer

Parallel β-sheets have adjacent strands running in the same direction, while antiparallel β-sheets have strands running in opposite directions.

Question 19

Which of the following is a method used in vivo to prevent protein denaturation?

Accepted Answer

Maintaining optimum temperature and pH through buffer systems

Comprehensive Study Notes on Proteins and Amino Acids

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