Question 1

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

Accepted Answer

The linear sequence of amino acids linked by peptide bonds, determined by the genetic code.

Question 2

A patient with a genetic mutation that alters a single amino acid in a protein experiences severe symptoms. Which protein structure level is directly affected by this mutation?

Accepted Answer

Primary structure

Question 3

Which of the following amino acids is considered essential and must be obtained from the diet?

Accepted Answer

Lysine

Question 4

During protein digestion, which enzyme is responsible for hydrolyzing peptide bonds in the stomach?

Accepted Answer

Pepsin

Question 5

Which of the following best explains why methionine is classified as an essential amino acid?

Accepted Answer

It cannot be synthesized by the body and must be obtained from dietary sources.

Question 6

Which of the following statements about branched-chain amino acids (BCAAs) is correct?

Accepted Answer

BCAAs include leucine, isoleucine, and valine, and are important for muscle protein synthesis.

Question 7

A person with a diet deficient in tryptophan may experience problems with which of the following?

Accepted Answer

Serotonin and melatonin synthesis

Question 8

Which of the following best describes the role of hydrochloric acid (HCl) in protein digestion in the stomach?

Accepted Answer

It denatures protein structures and activates pepsinogen to pepsin.

Question 9

Which of the following is a conditionally essential amino acid that becomes essential during severe illness or trauma?

Accepted Answer

Arginine

Question 10

Which of the following enzymes is activated in the small intestine and is responsible for cleaving peptide bonds adjacent to positively charged amino acids?

Accepted Answer

Trypsin

Question 11

A patient with phenylketonuria (PKU) cannot metabolize phenylalanine. Which of the following dietary recommendations is most appropriate?

Accepted Answer

Restrict foods high in phenylalanine and supplement with tyrosine.

Question 12

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

Accepted Answer

The overall three-dimensional arrangement of a single polypeptide chain due to side chain interactions.

Question 13

Which of the following is NOT a function of proteins in the human body?

Accepted Answer

Serving as a primary energy storage molecule.

Question 14

Which of the following statements about non-essential amino acids is correct?

Accepted Answer

They can be synthesized by the body in sufficient quantities under normal conditions.

Question 15

Which of the following best explains why a deficiency in lysine can impair collagen formation and tissue repair?

Accepted Answer

Lysine is involved in collagen cross-linking and protein synthesis.

Question 16

Which of the following processes is responsible for the endogenous synthesis of non-essential amino acids?

Accepted Answer

Transamination

Question 17

A patient recovering from severe burns is prescribed a diet high in which conditionally essential amino acid to support wound healing?

Accepted Answer

Proline

Question 18

Which of the following best describes the role of brush border peptidases in protein digestion?

Accepted Answer

They break down oligopeptides into dipeptides, tripeptides, and free amino acids for absorption.

Question 19

Which of the following amino acids is a precursor for neurotransmitters such as dopamine, norepinephrine, and epinephrine?

Accepted Answer

Phenylalanine

Question 20

Which of the following is the correct order of events in protein digestion from ingestion to absorption?

Accepted Answer

Mechanical digestion in the mouth → Denaturation by HCl in the stomach → Pepsin hydrolyzes peptide bonds → Pancreatic proteases act in the small intestine → Brush border enzymes complete digestion → Absorption of amino acids

Proteins and Amino Acids: Structure, Function, and Digestion

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