Question 1

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 2

A patient is exposed to high fever, which leads to the denaturation of enzymes in their body. What is the most likely consequence of enzyme denaturation?

Accepted Answer

The enzyme loses its three-dimensional shape, resulting in loss of catalytic activity.

Question 3

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

Accepted Answer

Methionine

Question 4

The lock and key model of enzyme action suggests that:

Accepted Answer

The enzyme's active site is complementary in shape to the substrate, allowing precise binding.

Question 5

Which equation represents the Michaelis-Menten model for enzyme kinetics?

Accepted Answer

$v = \frac{V_{max}[S]}{K_m + [S]}$

Question 6

Competitive inhibitors affect enzyme activity by:

Accepted Answer

Competing with the substrate for binding at the active site.

Question 7

Which of the following statements about feedback inhibition is correct?

Accepted Answer

The end product of a metabolic pathway inhibits the first enzyme in the pathway.

Question 8

Which of the following is a property of allosteric enzymes?

Accepted Answer

Their activity can be regulated by molecules binding at sites other than the active site.

Question 9

A protein is exposed to a strong acid. Which level(s) of protein structure are most likely to be disrupted?

Accepted Answer

Secondary, tertiary, and quaternary structures.

Question 10

Which of the following best explains why enzymes are highly specific for their substrates?

Accepted Answer

Enzymes have active sites with unique shapes and chemical properties that match specific substrates.

Question 11

Which of the following modifications can convert a proenzyme into its active form?

Accepted Answer

Cleavage of a specific peptide bond.

Question 12

Which of the following is NOT a function of proteins in living organisms?

Accepted Answer

Storing genetic information.

Question 13

A scientist is studying an enzyme that is regulated by phosphorylation. This is an example of:

Accepted Answer

Protein modification.

Question 14

Which of the following statements about noncompetitive inhibitors is true?

Accepted Answer

They bind to a site other than the active site and decrease the enzyme's activity.

Question 15

Which of the following amino acids is most likely to be found in the interior of a globular protein?

Accepted Answer

Leucine

Question 16

An enzyme-catalyzed reaction is measured at different substrate concentrations. The initial velocity ($v$) increases rapidly at low $[S]$, but levels off at high $[S]$. This behavior is best explained by:

Accepted Answer

The enzyme is saturated with substrate and operates at $V_{max}$.

Question 17

Which of the following best describes the induced fit model of enzyme activity?

Accepted Answer

The substrate induces a conformational change in the enzyme, improving binding and catalysis.

Question 18

Which of the following is a consequence of protein denaturation in food preparation, such as cooking an egg?

Accepted Answer

The protein unfolds and loses its native three-dimensional structure.

Question 19

Which of the following factors does NOT directly affect enzyme activity?

Accepted Answer

Genetic code sequence

Question 20

A mutation causes a change in the amino acid sequence of an enzyme. Which level of protein structure is directly affected?

Accepted Answer

Primary structure

Proteins and Enzymes: Structure, Function, and Regulation

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