Life Sciences Interview Questions and Answers focuses on “Enzymes – 2”.
1. Which of the following function is catalyzed by Racemases?
A. Removal of water
B. Intramolecular transfer of a functional group
C. Interconversion of L and D stereoisomers
D. Inversion of asymmetric carbon atom
Answer: C
Clarification: Racemases are the class of Isomerases which catalyzes the intramolecular rearrangement and interconvert L and D stereoisomers. Like racemases another isomerase which catalyzes the intramolecular transfer of functional group is mutases.
2. The zymogen is an inactive precursor of an active enzyme.
A. True
B. False
Answer: A
Clarification: Inactive precursor is first cleaved to form active enzyme and this inactive precursor is known as a zymogen. Many proteolytic enzymes are first synthesized as an inactive precursor which further cleaved to form the active enzyme.
3. Which of the following is an example of ligases enzyme?
A. Mutases
B. Epimerases
C. Racemases
D. Carboxylases
Answer: D
Clarification: Carboxylases are the example of ligases enzyme. Ligases are the class of enzyme which deals with the formation of C-C, C-S, C-O and C-N bonds.
4. What is the binding energy?
A. Free energy released in the formation of enzyme-substrate interaction
B. The energy required to form a bond
C. The energy required to bind substrate
D. It is the activation energy
Answer: A
Clarification: Binding energy is the free energy released when the enzyme-substrate complex is formed. This energy is used to lessen the activation energy. Binding energy can be maximum when the only correct substrate binds to the enzyme.
5. Which of the following is INCORRECT for the lock-and-key model?
A. It is used to describe the binding process
B. The active site of the enzyme is complementary to the substrate
C. It demonstrates enzyme-substrate complex
D. The binding of the substrate produces a conformational change in enzyme
Answer: D
Clarification: Lock-and-key model is used to describe the enzyme-substrate complex. It is the binding process where the active site of an enzyme is complementary to the shape of the substrate. The binding of the substrate produces a conformational change in the enzyme is incorrect as the confirmation of enzyme changes only in the induced fit model.
6. Which of the following is not a catalytic strategy for an enzyme to perform specific reaction?
A. Covalent catalysis
B. Metal ion catalysis
C. Michaelis constant
D. Acid-base catalysis
Answer: C
Clarification: Enzymes involves more than one strategies to catalyze specific reactions. Acid-base catalysis, metal ion catalysis, and covalent catalysis are best-characterized mechanisms employed by an enzyme.
7. What is the SI unit of enzyme activity?
A. Km
B. Kat
C. Kcat
D. Vmax
Answer: B
Clarification: Kat stands for katal, SI unit of enzyme activity. One katal is equals to the amount of enzyme that catalyzes the transformation of 1 mole of substrate per second. 1 katal = 1 mol sec-1.
8. Which of the following is not an example of irreversible enzyme inhibitor?
A. Cyanide
B. Sarin
C. Diisopropyl phosphoflouridate (DIPF)
D. Statin drugs
Answer: D
Clarification: Irreversible inhibitor binds to the active site of the enzyme and destroys the functional group. These inhibitors are mostly toxic in nature. Statin drugs are the example of competitive inhibitors which is used to control cholesterol.
9. Lineweaver-Burk plot is also known as______
A. Double reciprocal plot
B. Hanes-Woolf plot
C. Eadie-Hofstee plot
D. Steady-state equation
Answer: A
Clarification: Lineweaver-Burk plot is a double reciprocal plot as it is the reciprocal of Michaelis-Menten equation represented in the graphical form.
1/V = Km/Vmax [S] + 1/Vmax.
10. Name the enzyme which is found in tears, sweat, and an egg white?
A. Ribozyme
B. Lysozyme
C. Zymogen
D. Isozymes
Answer: B
Clarification: Lysozyme is an enzyme which is present in secretions such as tears, sweat and found in egg white. Lysozyme cleaves the glycosidic bond that connects NAG and NAM of peptidoglycan cell wall.
11. What is an Isozyme?
A. Same structure, different function
B. Different structure, the same function
C. Same structure, the same function
D. Different structure, different function
Answer: B
Clarification: Isozymes are multiple forms of enzymes that have the same functions but differ in structure. For example, lactate dehydrogenase which catalyzes the conversion of pyruvate to lactate, it has five isoenzymes.
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