MCAT Biological and Biochemical Foundations of Living Systems Quiz: 1a Enzyme Kinetics Regulation

What this quiz covers

This quiz focuses on 1a Enzyme Kinetics Regulation, giving you a quick way to practice the rules, question types, and explanations that matter most for MCAT Biological and Biochemical Foundations of Living Systems.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

Question 1

1. Increased membrane glucose transport causing higher extracellular glucose
2. High ATP and high citrate indicating abundant energy
3. High NADH/NAD$^+$ ratio indicating reduced electron transport
4. Low cellular energy charge with elevated AMP relative to ATP (correct answer)

Question 2

1. Increase pH to deprotonate EDTA and reduce its affinity
2. Add more substrate to overcome competitive inhibition by EDTA
3. Decrease enzyme concentration to reduce EDTA binding
4. Add Mg$^{2+}$ in excess to overcome chelation and restore catalysis (correct answer)

Question 3

1. Competitive inhibition (correct answer)
2. Uncompetitive inhibition
3. Noncompetitive inhibition
4. Product inhibition that increases $V_{max}$

Question 4

1. Allosteric activation that increases catalytic efficiency or substrate affinity (correct answer)
2. Increased transcription of the enzyme gene leading to higher $V_{max}$
3. Increased translation of the enzyme mRNA leading to more enzyme molecules
4. Decreased substrate transport into the reaction vessel

Question 5

1. Competitive inhibition versus A
2. Noncompetitive inhibition versus A (correct answer)
3. Competitive inhibition versus B (therefore $K_m$ for A must increase)
4. Uncompetitive inhibition versus A (therefore $K_m$ for A must decrease)

Question 6

1. Stays the same (correct answer)
2. Increases 2-fold
3. Decreases 2-fold
4. Increases 4-fold

Question 7

1. Allosteric activation
2. Feedback inhibition
3. Competitive inhibition
4. Covalent phosphorylation (correct answer)

Question 8

1. 0.9 mM
2. 3.6 mM
3. 7.2 mM (correct answer)
4. 8.0 mM

Question 9

1. Competitive inhibition
2. Allosteric inhibition (correct answer)
3. Noncompetitive inhibition
4. Irreversible inhibition

Question 10

1. 0.33
2. 0.50 (correct answer)
3. 0.67
4. 1.00

Question 11

1. Uncompetitive inhibition that decreases both apparent $K_m$ and $V_{max}$
2. Competitive inhibition that increases apparent $K_m$ without changing $V_{max}$ (correct answer)
3. Noncompetitive inhibition that decreases $V_{max}$ without changing apparent $K_m$
4. Allosteric activation that decreases apparent $K_m$ and increases $V_{max}$

Question 12

1. Reduced substrate diffusion that lowers apparent $K_m$ and increases $V_{max}$
2. Irreversible active-site modification that reduces $V_{max}$ at all substrate concentrations
3. Competitive inhibition that increases apparent $K_m$ while maintaining a hyperbolic curve
4. Induction of cooperative substrate binding through allosteric regulation (correct answer)

Question 13

1. Citrate acts as an allosteric inhibitor that decreases apparent substrate affinity without changing catalytic capacity (correct answer)
2. Citrate acts as a competitive inhibitor at the active site that decreases $V_{max}$ but not apparent $K_m$
3. Citrate acts as a noncompetitive inhibitor that decreases both apparent $K_m$ and $V_{max}$
4. Citrate increases PFK-1 activity by stabilizing the high-affinity (R) state, lowering apparent $K_{0.5}$

Question 14

1. It becomes 100% of the original $V_{max}$ because $K_m$ is unchanged
2. It remains 50% of the original $V_{max}$
3. It becomes 75% of the original $V_{max}$
4. It becomes 25% of the original $V_{max}$ (correct answer)

Question 15

1. Covalent modification increases catalytic turnover ($k_{cat}$) without altering substrate binding affinity (correct answer)
2. Competitive inhibition is relieved, decreasing $K_m$ and increasing $V_{max}$
3. Increased substrate transport into hepatocytes lowers apparent $K_m$ without affecting $V_{max}$
4. Gene transcription increases enzyme concentration, primarily decreasing $K_m$ within 10 minutes

Question 16

1. Addition of fructose-1,6-bisphosphate as an allosteric activator (correct answer)
2. Further increasing alanine concentration to shift equilibrium toward product formation
3. Decreasing pH to protonate alanine and enhance inhibitory binding
4. Lowering phosphoenolpyruvate to reduce substrate saturation and overcome inhibition

Question 17

1. Increased apparent $K_m$ and increased $V_{max}$
2. Increased apparent $K_m$ and unchanged $V_{max}$
3. Unchanged apparent $K_m$ and decreased $V_{max}$
4. Decreased apparent $K_m$ and decreased $V_{max}$ (correct answer)

Question 18

1. Add more inhibitor to shift binding toward the enzyme–inhibitor complex
2. Decrease enzyme concentration to reduce inhibitor binding sites
3. Increase PABA concentration substantially above $K_m$ (correct answer)
4. Lower temperature to increase collision frequency and overcome inhibition

Question 19

1. Lowering temperature to increase collision frequency and raise $V_{max}$
2. Decreasing substrate concentration to reduce binding of Z at the allosteric site
3. Adding a noncompetitive inhibitor to restore the original curve shape
4. Increasing substrate concentration to favor the high-activity state despite the allosteric inhibitor (correct answer)

Question 20

1. Competitive inhibition, because the x-intercept shifts toward zero
2. Noncompetitive inhibition, because the y-intercept increases while the x-intercept is unchanged (correct answer)
3. Uncompetitive inhibition, because both intercepts shift in parallel
4. Allosteric activation, because $1/V_{max}$ decreases