Enzymes MCQs set 3 for AKU Entry Test Biology — 20 solved questions.
Q1. Certain microorganisms can survive in extremely hot environments due to the presence of thermostable enzymes. What characteristic allows these enzymes to function optimally at high temperatures?
Answer: High melting point
Explanation: Thermostable enzymes have high melting points, most tempting wrong is Allosteric regulation
Q2. A researcher is studying the effects of pH on enzyme activity. Which of the following enzymes is most likely to be active at a pH of 8?
Answer: Trypsin
Explanation: Trypsin is active at alkaline pH, most tempting wrong is Pepsin
Q3. Some enzymes can catalyze reactions in both the forward and reverse directions. What is this property known as?
Answer: Reversibility
Explanation: Reversibility allows enzymes to catalyze both forward and reverse reactions, most tempting wrong is Irreversibility
Q4. A particular enzyme has a Km of 0.1 mM and a Vmax of 100 μmol/min. What is the substrate concentration at which the enzyme reaches half of its maximum velocity?
Answer: 0.1 mM
Explanation: Km is the substrate concentration at which enzyme reaches half of Vmax, most tempting wrong is 0.01 mM
Q5. Some enzymes require the presence of a non-protein molecule to be active. What is this molecule known as?
Answer: Coenzyme
Explanation: Coenzymes are non-protein molecules required for enzyme activity, most tempting wrong is Cofactor
Q6. A certain enzyme is inhibited by a molecule that binds to a site other than the active site. What type of inhibition is this?
Answer: Non-competitive inhibition
Explanation: Non-competitive inhibition occurs when inhibitor binds to a site other than the active site, most tempting wrong is Competitive inhibition
Q7. Some enzymes can be activated by the binding of a molecule to a specific site. What is this type of regulation known as?
Answer: Allosteric regulation
Explanation: Allosteric regulation involves the binding of a molecule to a specific site, most tempting wrong is Covalent modification
Q8. A researcher is studying the effects of temperature on enzyme activity. Which of the following enzymes is most likely to be active at a temperature of 50°C?
Answer: Thermolysin
Explanation: Thermolysin is a thermostable enzyme, most tempting wrong is Protease
Q9. Some enzymes can catalyze reactions in the presence of a specific ion. What is this type of enzyme known as?
Answer: Metalloenzyme
Explanation: Metalloenzymes require a specific ion to be active, most tempting wrong is Oxidoreductase
Q10. A certain enzyme has a high turnover number, indicating that it can catalyze a large number of reactions per unit time. What is the advantage of this property?
Answer: Increased reaction rate
Explanation: High turnover number indicates a high reaction rate, most tempting wrong is Increased substrate affinity
Q11. Some enzymes can be inhibited by the binding of a molecule to the active site. What type of inhibition is this?
Answer: Competitive inhibition
Explanation: Competitive inhibition occurs when inhibitor binds to the active site, most tempting wrong is Non-competitive inhibition
Q12. Some enzymes can catalyze reactions that involve the transfer of a functional group. What is this type of enzyme known as?
Answer: Transferase
Explanation: Transferases catalyze reactions involving the transfer of a functional group, most tempting wrong is Oxidoreductase
Q13. A certain enzyme is inhibited by a molecule that binds to the enzyme and reduces its activity. What type of inhibition is this?
Answer: Non-competitive inhibition
Explanation: Non-competitive inhibition occurs when inhibitor binds to the enzyme and reduces its activity, most tempting wrong is Competitive inhibition
Q14. A researcher is studying the effects of substrate concentration on enzyme activity. Which of the following enzymes is most likely to be saturated at a substrate concentration of 10 mM?
Answer: Trypsin
Explanation: Trypsin is likely to be saturated at high substrate concentrations, most tempting wrong is Amylase
Q15. Some enzymes can catalyze reactions that involve the breakdown of a molecule into two or more products. What is this type of enzyme known as?
Answer: Lyase
Explanation: Lyases catalyze reactions involving the breakdown of a molecule, most tempting wrong is Hydrolase
Q16. A certain enzyme has a low Km, indicating that it has a high affinity for its substrate. What is the advantage of this property?
Answer: Increased substrate affinity
Explanation: Low Km indicates high substrate affinity, most tempting wrong is Increased reaction rate
Q17. Some enzymes can be inhibited by the binding of a molecule to the enzyme and altering its conformation. What is this type of inhibition known as?
Answer: Allosteric inhibition
Explanation: Allosteric inhibition occurs when inhibitor binds to the enzyme and alters its conformation, most tempting wrong is Competitive inhibition
Q18. A researcher is studying the effects of enzyme concentration on reaction rate. Which of the following enzymes is most likely to exhibit a linear relationship between enzyme concentration and reaction rate?
Answer: Amylase
Explanation: Amylase is likely to exhibit a linear relationship between enzyme concentration and reaction rate, most tempting wrong is Trypsin
Q19. During a high-intensity workout, a person's muscle cells rely on anaerobic glycolysis for energy. What enzyme is responsible for the first committed step of this process?
Answer: Phosphofructokinase-1
Explanation: Phosphofructokinase-1 is the key regulatory enzyme, Hexokinase is similar but not specific to glycolysis
Q20. An enzyme has a Km of 0.1 mM and Vmax of 100 μmol/min. What is the most likely explanation if the enzyme's activity increases with higher substrate concentrations up to 1 mM?
Answer: The enzyme is not saturated at 1 mM substrate
Explanation: Km is the substrate concentration at half Vmax, so the enzyme is not saturated at 1 mM