Question 1

Which of the following best describes a zwitterion form of an amino acid at physiological pH?

Accepted Answer

A molecule with both a positively charged amino group and a negatively charged carboxyl group.

Question 2

Which of the following statements about protein structure is CORRECT?

Accepted Answer

The secondary structure includes $$\alpha-$$helices and $$\beta-$$sheets stabilized by hydrogen bonds along the backbone.

Question 3

Which of the following amino acids is achiral?

Accepted Answer

Glycine

Question 4

A peptide bond is formed between which two functional groups of adjacent amino acids?

Accepted Answer

The carboxyl group of one amino acid and the amino group of the next

Question 5

Which of the following best explains why proteins denature when exposed to high temperatures?

Accepted Answer

Heat disrupts non-covalent interactions such as hydrogen bonds, causing loss of secondary, tertiary, and quaternary structure.

Question 6

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

Accepted Answer

All of the above

Question 7

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 electric charge

Question 8

Which of the following statements about peptide hydrolysis is TRUE?

Accepted Answer

Peptide hydrolysis breaks peptide bonds to yield amino acids.

Question 9

A patient is diagnosed with a genetic disorder that causes a single amino acid substitution in hemoglobin. Which level of protein structure is directly affected by this mutation?

Accepted Answer

Primary structure

Question 10

Which of the following amino acids would be classified as basic?

Accepted Answer

Lysine

Question 11

Which of the following best describes the difference between fibrous and globular proteins?

Accepted Answer

Fibrous proteins are insoluble in water and form structural components, while globular proteins are soluble and have metabolic functions.

Question 12

Which of the following intermolecular forces is responsible for the formation of disulfide bonds in proteins?

Accepted Answer

Covalent bonds between sulfur atoms of cysteine residues

Question 13

Trypsin is an enzyme that hydrolyzes peptide bonds at the carboxyl side of which type of amino acids?

Accepted Answer

Basic amino acids such as lysine and arginine

Question 14

Which of the following best explains why the sequence of amino acids in a protein is crucial to its function?

Accepted Answer

The sequence determines the protein's three-dimensional structure, which is essential for its function.

Question 15

Which of the following best describes what happens to an amino acid in a solution with a pH much lower than its isoelectric point ($$pI$$)?

Accepted Answer

The amino acid will have a net positive charge due to protonation of the amino and carboxyl groups.

Question 16

Which of the following is a conjugated protein?

Accepted Answer

Myoglobin, because it contains a heme group

Question 17

Which of the following best describes the process of denaturation?

Accepted Answer

Loss of secondary, tertiary, and quaternary structure without breaking peptide bonds

Question 18

A dipeptide is formed from the condensation of two amino acids. Which of the following is a byproduct of this reaction?

Accepted Answer

Water ($$H_2O)$$

Question 19

Which of the following best describes the role of hydrogen bonding in the secondary structure of proteins?

Accepted Answer

Hydrogen bonds stabilize $$\alpha-$$helices and $$\beta-$$sheets by forming between backbone atoms.

Question 20

Which of the following is TRUE about the amino terminal (N-terminal) of a protein?

Accepted Answer

It is the end of the protein with a free $$NH_2$$ group.

Amino Acids and Proteins: Structure, Properties, and Functions

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