Question 1

Which of the following best explains why hydrophobic amino acids are typically found in the interior of globular proteins?

Accepted Answer

Hydrophobic amino acids are repelled by the aqueous environment, causing them to cluster inside the protein away from water.

Question 2

Which type of bond is primarily responsible for stabilizing the secondary structure of proteins, such as alpha helices and beta sheets?

Accepted Answer

Hydrogen bonds

Question 3

A mutation replaces a cysteine residue with a serine in a protein. Which level of protein structure is most likely to be directly affected by this change?

Accepted Answer

Tertiary structure

Question 4

Which of the following statements about enzyme catalysis is correct?

Accepted Answer

Enzymes lower the activation energy ($E_a$) and increase the rate of reaction without being consumed.

Question 5

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

Accepted Answer

The enzyme changes shape slightly to better fit the substrate upon binding.

Question 6

A researcher is studying an enzyme-catalyzed reaction and observes that increasing substrate concentration does not increase the reaction rate beyond a certain point. What is the most likely explanation?

Accepted Answer

The enzyme has reached saturation; all active sites are occupied.

Question 7

Which of the following equations represents the Michaelis-Menten equation for enzyme kinetics?

Accepted Answer

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

Question 8

In a Lineweaver-Burk plot, what does the y-intercept represent?

Accepted Answer

$1/V_{max}$

Question 9

A competitive inhibitor affects enzyme kinetics in which of the following ways?

Accepted Answer

It increases $K_m$ but does not change $V_{max}$.

Question 10

Which of the following amino acids is most likely to form a disulfide bridge in a protein's tertiary structure?

Accepted Answer

Cysteine

Question 11

A patient has a genetic mutation that causes the replacement of a glutamic acid residue with valine in hemoglobin. This change is most likely to affect which property of the protein?

Accepted Answer

The protein's solubility and folding due to altered side chain properties

Question 12

Which of the following best describes the effect of a noncompetitive inhibitor on enzyme kinetics?

Accepted Answer

It decreases $V_{max}$ but does not change $K_m$.

Question 13

Which of the following experimental techniques is most appropriate for separating proteins based on both their isoelectric point and molecular weight?

Accepted Answer

2-Dimensional Gel Electrophoresis (2-D Gel)

Question 14

Which of the following interactions is NOT typically involved in stabilizing the tertiary structure of proteins?

Accepted Answer

Peptide bonds

Question 15

A scientist treats a protein with trypsin, which cleaves at the carboxyl side of lysine and arginine residues. What is the most likely result of this treatment?

Accepted Answer

The protein will be cleaved into smaller peptide fragments at lysine and arginine residues.

Question 16

Which of the following amino acids is classified as having a polar but uncharged side chain?

Accepted Answer

Serine

Question 17

Which of the following best explains the effect of pH on enzyme activity?

Accepted Answer

Each enzyme has an optimal pH at which its activity is maximal; deviations can denature the enzyme or alter active site charge.

Question 18

Which of the following is a correct statement about allosteric regulation of enzymes?

Accepted Answer

Allosteric regulators bind to a site other than the active site, causing a conformational change that affects enzyme activity.

Question 19

A researcher is analyzing enzyme kinetics and finds that the presence of an inhibitor does not change the $K_m$ but decreases the $V_{max}$. What type of inhibition is most likely occurring?

Accepted Answer

Noncompetitive inhibition

Question 20

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

Accepted Answer

The arrangement of multiple polypeptide subunits in a multi-subunit protein complex.

Protein Structure and Function: Cell Biology Study Notes

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