Enzymology MCQ | Biochemistry MCQ

1. Constitutive enzymes are 

A) repressed by repressors 

B) always produced in the cell

C) encoded by sequences that occurs as part of an operon

D) induced by effector molecules


2. Name the compound with greatest standard free energy

A) ATP 

B) Phosphocreatine

C) Phosphoenol pyruvate 

D) cAMP


 3. In a competitive inhibition the Km and Vmax values of an enzyme


A) Km and Vmax values decrease

B) Km value increases whereas Vmax remains unchanged

C) Km and Vmax values increase

D) Km value remains unchanged and Vmax value decreases


4. Inactive precursors of certain proteolytic enzymes

A) Abzymes 

B) Allozymes

C) Isozymes 

D) Zymogens

5. Line Weaver – Burk plot helps to find out

A) Rate of enzyme action 

B) Competitive inhibitor

C) Substrate composition 

D) Group specificity

6. In a normal metabolic pathway substance Z is produced from X through the intermediate Y and involvement of two enzymes, A and B respectively. If both enzymes are functional, what would be the most possible consequence?

A) Substance Z accumulates 

B) Substance X accumulates

C) Enzyme A accumulates 

D) Enzyme B accumulates


7. The metal component of Nitrogenase enzyme is

A) Manganese 

B) Molybdenum

C) Copper 

D) Zinc


8.The Michaelis -Menten Constant KM is measure is 

A) The rate of the reaction

B) The affinity of the enzyme for the substrate

C) The concentration of the enzyme substrate intermediate

D) None of the above

9. Identify the enzyme which catalyzes substrate level phosphorylation reaction in TCA cycle.

A) Isocitrate dehydrogenase

 B) Aconitase

C) Succinate thiokinase 

D) Fumarase

10. A researcher isolated amylase from the pancreas of an experimental rat and 20 μ
l of the enzyme preparation showed an activity of 0.5 Units when allowed to react for 1 minute. The concentration of the protein in the enzyme preparation was 0.25 mg/ml. Find out the specific activity of the enzyme preparation? 

(A) 0.1 Units/mg 

(B) 1 Unit/mg 

(C) 10 Units/mg

 (D) 100 Units/mg 

Answer:

1. B) always produced in the cell

2.  C) Phosphoenol pyruvate 

3. B) Km value increases whereas Vmax remains unchanged

4. D) Zymogens

5. B) Competitive inhibitor

6. A) Substance Z accumulates 

7. B) Molybdenum

8. B) The affinity of the enzyme for the substrate

9. C) Succinate thiokinase 

10.(D) 100 Units/mg

Solution:

Units enzyme: 0.5 units

Volume: 20 µl

Protein concentration: 0.25 mg/ml

Specific activity = enzyme units / (vol. in µl x (protein conc. in mg per ml / 1000))

=0.5/[20x(0.25/1000)] =100 Units/mg

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