Question 1

Which of the following statements best explains why ATP hydrolysis is highly exergonic under physiological conditions?

Accepted Answer

The products of ATP hydrolysis (ADP and Pi) are stabilized by resonance and greater solvation, and there is a decrease in electrostatic repulsion.

Question 2

A solution contains 0.3 mol of acetic acid ($$CH_3COOH) $$and 0.01 mol of sodium acetate ($$CH_3COONa) in 1 L. If $$the $$pK_a of $$acetic acid is 4.76, what is the pH of the solution? Use the Henderson-Hasselbalch equation.

Accepted Answer

$$pH = 4.76 + \log_{10} \left( \frac{0.01}{0.3} \right )$$

Question 3

Which of the following best describes the role of magnesium ions ($$Mg^{2+}) in $$ATP-dependent enzymatic reactions?

Accepted Answer

They stabilize the negative charges on the phosphate groups of ATP.

Question 4

Which of the following statements about enzyme active sites is correct?

Accepted Answer

Active sites bind substrates through multiple weak interactions such as hydrogen bonds and van der Waals forces.

Question 5

A competitive inhibitor of an enzyme will:

Accepted Answer

Increase $$K_m$$ but not affect $$V_{max}$$

Question 6

Which of the following best explains why the hydrolysis of phosphoenolpyruvate (PEP) is more exergonic than that of ATP?

Accepted Answer

PEP hydrolysis produces pyruvate, which undergoes tautomerization, stabilizing the product.

Question 7

If a reaction has a $$\Delta G^\circ' of$$ $$-30 kJ/$$mol and is coupled to a reaction with $$\Delta G^\circ' of$$ $$+20 kJ/$$mol, what is the overall $$\Delta G^\circ'$$ for the coupled reaction?

Accepted Answer

$$-10 kJ/$$mol

Question 8

Which of the following statements about the Michaelis-Menten equation is correct?

Accepted Answer

It describes the rate of enzyme-catalyzed reactions as a function of substrate concentration.

Question 9

Which of the following amino acids would be present in a titration curve with three distinct buffering regions?

Accepted Answer

Lysine

Question 10

Which of the following best describes the effect of adding salt to water on the solubility of nonpolar molecules?

Accepted Answer

It decreases the solubility of nonpolar molecules by enhancing the hydrophobic effect.

Question 11

Which of the following statements about the structure of DNA is correct?

Accepted Answer

The two strands are antiparallel and held together by hydrogen bonds between complementary bases.

Question 12

Which of the following is NOT a function of binding energy in enzyme-catalyzed reactions?

Accepted Answer

Increasing the entropy of the substrate.

Question 13

Which of the following molecules is NOT used as a substrate in a reaction that requires thiamine pyrophosphate as a coenzyme?

Accepted Answer

Glucose-6-phosphate

Question 14

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

Accepted Answer

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

Question 15

Which of the following statements about the hydrophobic effect is correct?

Accepted Answer

It results from the increase in entropy of water molecules when nonpolar molecules aggregate.

Question 16

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

Accepted Answer

Enzymes bind substrates through multiple weak interactions that are optimized for the transition state.

Question 17

Which of the following is a correct statement about the effect of pH on enzyme activity?

Accepted Answer

Each enzyme has an optimal pH at which its activity is maximal.

Question 18

Which of the following best describes the role of NAD+ in cellular metabolism?

Accepted Answer

It acts as an oxidizing agent, accepting electrons during the oxidation of substrates.

Question 19

Which of the following statements about the electron transport chain is correct?

Accepted Answer

Electrons are transferred from NADH and FADH2 to oxygen through a series of protein complexes.

Comprehensive Review of Biochemistry I: Key Concepts and Applications

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