Question 1

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

Accepted Answer

The sequence of amino acids joined by peptide bonds in a polypeptide chain.

Question 2

Which of the following amino acids is classified as nonpolar?

Accepted Answer

Valine

Question 3

A patient is diagnosed with sickle-cell anemia. Which change in the hemoglobin protein is responsible for this disease?

Accepted Answer

A polar acidic glutamic acid is replaced by a nonpolar valine in the beta chain.

Question 4

Which of the following is true about essential amino acids?

Accepted Answer

They must be obtained from dietary proteins.

Question 5

Which type of protein structure is stabilized primarily by hydrogen bonds between backbone atoms, forming either a spiral or a sheet-like arrangement?

Accepted Answer

Secondary structure

Question 6

Which of the following interactions is responsible for the formation of disulfide bonds in the tertiary structure of proteins?

Accepted Answer

Covalent bonds between cysteine residues

Question 7

A competitive inhibitor affects enzyme activity by:

Accepted Answer

Competing with the substrate for the active site due to structural similarity.

Question 8

Which of the following best describes the effect of increasing substrate concentration on enzyme activity when the enzyme is saturated?

Accepted Answer

The reaction rate reaches a maximum and does not increase further.

Question 9

Which of the following is a function of globular proteins?

Accepted Answer

Transporting oxygen in the blood

Question 10

Which of the following statements about enzyme cofactors is correct?

Accepted Answer

Cofactors can be metal ions or organic molecules called coenzymes.

Question 11

Which of the following best describes the effect of temperature on enzyme activity in the human body?

Accepted Answer

Enzyme activity is highest at the optimum temperature, usually around 37 °C.

Question 12

Which of the following is an example of a protein denaturation process?

Accepted Answer

Cooking an egg, causing the egg white to solidify

Question 13

Which class of enzyme catalyzes the hydrolysis of peptide bonds in proteins?

Accepted Answer

Hydrolases

Question 14

A patient is exposed to mercury ions (Hg$$^{2+}$$), which bind to the sulfur atoms in cysteine residues of enzymes. What type of inhibition is this?

Accepted Answer

Irreversible inhibition

Question 15

Which of the following vitamins is water-soluble and required for collagen synthesis?

Accepted Answer

Vitamin C

Question 16

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

Accepted Answer

The arrangement and interaction of multiple polypeptide subunits.

Question 17

Which of the following is a correct statement about fat-soluble vitamins?

Accepted Answer

They are stored in body fat and can accumulate to toxic levels.

Question 18

Which of the following interactions is responsible for salt bridges in the tertiary structure of proteins?

Accepted Answer

Ionic bonds between acidic and basic side chains

Question 19

Which of the following best describes the induced-fit model of enzyme action?

Accepted Answer

The enzyme's active site is flexible and adjusts to fit the substrate, improving catalysis.

Question 20

A solution has $$[H_3O^+] = 1 	imes 10$$^{-5}$$ M. What is the pH of the solution?

Accepted Answer

$$pH = 5$$

Amino Acids, Proteins, and Enzymes: Structure, Function, and Biological Importance

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