Question 1

Which level of protein structure is primarily stabilized by hydrogen bonds between the peptide backbone, and what is a common example of this structure?

Accepted Answer

Secondary structure; alpha helices and beta sheets

Question 2

A patient is diagnosed with sickle cell anemia, which is caused by a single amino acid substitution in the hemoglobin protein. This mutation most directly affects which level of protein structure?

Accepted Answer

Primary structure

Question 3

Which of the following best describes the function of enzymes in biological systems?

Accepted Answer

They speed up chemical reactions without being consumed.

Question 4

The Michaelis-Menten constant ($K_m$) is defined as:

Accepted Answer

The substrate concentration at which the reaction rate is half of $V_{max}$.

Question 5

Which of the following statements about competitive and noncompetitive enzyme inhibitors is correct?

Accepted Answer

Competitive inhibitors increase $K_m$ but do not affect $V_{max}$.

Question 6

A scientist is studying an enzyme-catalyzed reaction. She finds that increasing the substrate concentration does not increase the reaction rate beyond a certain point. This plateau is best explained by:

Accepted Answer

All enzyme active sites are saturated with substrate ($V_{max}$ is reached).

Question 7

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

Accepted Answer

Storing genetic information

Question 8

A mutation causes a prion protein to misfold, leading to the formation of beta sheets instead of alpha helices. This change is most likely to affect which property of the protein?

Accepted Answer

Its secondary structure

Question 9

Which of the following best explains why enzymes are considered reaction specific?

Accepted Answer

Enzymes only bind to substrates with a complementary shape to their active site.

Question 10

A researcher adds a noncompetitive inhibitor to an enzyme-catalyzed reaction. Which of the following changes would she expect to observe in the enzyme kinetics?

Accepted Answer

$V_{max}$ decreases, $K_m$ remains unchanged

Question 11

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

Accepted Answer

Enzyme activity is highest at an optimum temperature and decreases if the temperature is too high or too low.

Question 12

Salivary amylase functions best at a pH close to 7, while alkaline phosphatase functions best at a pH above 8. What does this suggest about enzyme adaptation?

Accepted Answer

Enzymes evolve to have pH optima that match their environment.

Question 13

Which of the following is an example of a protein with a quaternary structure?

Accepted Answer

Multiple polypeptide chains assembling to form hemoglobin

Question 14

A patient with a fever has an elevated body temperature. How might this affect the enzymes in their body?

Accepted Answer

Enzyme activity may decrease if the temperature exceeds the enzyme's optimum, potentially leading to denaturation.

Question 15

Which of the following best describes the role of ferritin in the body?

Accepted Answer

It stores iron for later use.

Question 16

A scientist is studying an enzyme with a $K_m$ of 2 mM and a $V_{max}$ of 100 $$mol/min. If a competitive inhibitor is added, which of the following changes would be expected?

Accepted Answer

$K_m$ increases, $V_{max}$ remains the same

Question 17

Which of the following is a real-world example of a disease caused by protein misfolding?

Accepted Answer

Creutzfeldt-Jakob disease

Question 18

Which of the following best explains why prion diseases are considered infectious?

Accepted Answer

Misfolded prion proteins induce normal proteins to misfold, spreading the disease.

Question 19

Which of the following best describes the relationship between enzyme concentration and reaction rate at saturating substrate levels?

Accepted Answer

Increasing enzyme concentration increases the reaction rate.

Question 20

A mutation in the gene encoding collagen results in a protein that cannot form its normal triple helix. Which level of protein structure is most directly affected?

Accepted Answer

Quaternary structure

Protein Structure and Enzyme Function: A Study Guide

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