1. : Aldolase belongs to ________ class of enzymes.
(A) Transferases
(B) Lyases
(C) Hydrolases
(D) Isomerases
2. : All of the following enzymes show group specificity, excluding
(A) Hexokinase
(B) Glucokinase
(C) Phospholipase
(D) Amino acid oxidase
3. : Pyruvate carboxylase belongs to ________ class of enzymes.
(A) Ligase
(B) Oxidoreductase
(C) Transferase
(D) Hydrolase
4. : The co-enzymes have which properties?
(A) Having the same quaternary structures like the enzymes
(B) Structural analogues of enzymes
(C) Soluble, colloidal, protein molecules
(D) Heat stable, dialyzable, non-protein organic molecules
5. : When substrate concentration is equal to Km of an enzyme:
(A) Half of the enzyme molecules are bound to the substrate
(B) The velocity of the reaction is = V
(C) The enzyme is saturated with the substrate
(D) The reaction velocity becomes independent of substrate concentration
6. : A sigmoidal plot of substrate concentration ([S]) versus reaction velocity (V) may indicate:
(A) Michaelis-Menten kinetics
(B) Non-competitive inhibition
(C) Competitive inhibition
(D) Co-operative binding
7. : An inducer is not needed in which type of enzyme?
(A) Allosteric enzyme
(B) Inducible enzyme
(C) Constitutive enzyme
(D) An isoenzyme
8. : The V of an enzyme represents which of the following?
(A) Substrate concentration
(B) The amount of active enzyme
(C) Half the substrate
(D) The total concentration of the enzymes
9. : Which is characteristic of a competitive inhibitor?
(A) It may be a feedback inhibitor
(B) It decreases the Vmax of the enzyme
(C) It interferes with the binding of the substrate to the active site
(D) It causes irreversible inhibition
10. : Enzymes which are produced inactive form in the living cells are called:
(A) Proenzymes
(B) Apoenzymes
(C) Lysozymes
(D) Ribozymes
11. : Which is a proenzyme?
(A) Angiotensin converting enzyme
(B) Pepsinogen
(C) None of these
Answer: (B) Pepsinogen
12. : The enzyme _______ that adds water across a double bond or removes water to create a double bond without breaking the bonds?
(A) Hydrolase
(B) Hydroxylase
(C) Hydratase
(D) Esterase
13. : Effect of raising the temperature from 20-80°C on enzyme activity would be:
(A) Increasing velocity
(B) Decreasing velocity
(C) Increasing followed by decreasing velocity
(D) Both A, B and C
14. : Cytochrome P-450 carries which type of enzyme?
(A) Monoamine oxidase
(B) Catalase
(C) Dehydrogenase
(D) Monooxygenase
15. : What is the most ideal statement regarding the ‘Active Site’ of an enzyme?
(A) Nearly all polypeptide chains must participate in catalysis
(B) Most of the amino acids involved in Active Site are located near each other on the polypeptide
(C) Conformation of the Active Site does not exist until the substrate binds
(D) Amino acids forming Active Site are in close proximity due to specific orientation in space
16. : Which of the following is an example of multifunctional enzyme?
(A) Acetyl-CoA carboxylase
(B) Pyruvate dehydrogenase complex
(C) Animal fatty acid synthase
(D) None of these
17. : An enzyme that converts an aldose sugar to a keto-sugar is classified as ______.
(A) Transferase
(B) Oxidoreductase
(C) Isomerase
(D) Hydrolase
18. : If the initial velocity of an enzymatic reaction is equal to Vmax, the substrate concentration is:
(A) Far above KM
(B) Equal to KM
(C) Half of K
(D) Both A, B and C
19. : During competitive inhibition, the inhibitor:
(A) Competes with the substrate
(B) Irreversibly binds with the enzyme
(C) Competes with the enzyme
(D) Both A, B and C
20. : Competitive inhibitors ______.
(A) Decrease the VMAX
(B) Decrease the KM of the enzyme for the substrate
(C) Increase the VMAX
(D) Increase the KM of the enzyme for the substrate
21. : Which is a therapeutic enzyme?
(A) Glucose-6-P dehydrogenase
(B) Streptokinase
(C) Monoamine oxidase
(D) Allopurinol
22. : The role of co-enzyme in enzymatic reactions is:
(A) Enhancing the specificity
(B) Increasing the number of binding sites on the Apo-enzyme
(C) Acting as an acceptor for intermediate products of the substrate
(D) None of these
23. : Which is not true regarding enzymes?
(A) They remain active even after separation from the source
(B) They are destroyed after completion of the reaction
(C) They are destroyed at high temperatures
(D) Their activity depends upon the pH of the solution
24. : Michaelis constant (Km) of an enzyme is ______.
(A) Dependent upon the enzyme concentration
(B) Numerically equal to substrate concentration at Vmax
(C) Numerically equal Vmax
(D) Independent of pH
25. : During the estimation of enzyme activity, all of the following are kept constant, excluding:
(A) Enzyme concentration
(B) pH
(C) Substrate concentration
(D) Temperature
26. : As per Michaelis-Menten equation, at a very low substrate concentration, the initial velocity of the enzymatic reaction is ________.
(A) Not affected by enzyme concentration
(B) Nearly equal to Vmax
(C) Inversely proportional to substrate concentration
(D) Directly proportional to substrate concentration
27. : The isoenzymes differ from each other in all of the following, excluding:
(A) Michaelis-Menten constant
(B) Specific inhibitors
(C) Amino acid sequence
(D) Catalytic activity
28. : What is Lock and Key Theory?
(A) The active site is flexible and adjusts to the substrate
(B) The structure of the substrate is identical to the active site
(C) The Enzyme-Substrate complex has higher energy than free substrate and enzyme
(D) The active site is complementary to the shape of the substrate
29. : Which was the first enzyme to be isolated, purified, and crystallized?
(A) Chymotrypsin
(B) Urease
(C) Lysozyme
(D) Ribonuclease
30. : The concept of “Induced Fit” as a theory implies which of the following?
(A) The template theory adequately explains the enzyme mechanism
(B) The catalytic groups are brought into proper alignment by the substrate
(C) The conformation of the substrate changes upon binding with the enzyme
(D) Formation of ES complex is always the fastest step
31. : The alloenzymes are
(A) Chemically and immunologically different forms of the enzymes
(B) The same enzyme isolated from different tissues or subcellular compartments
(C) Structurally related enzyme that carry out different reactions
(D) Chemically identical enzymes isolated from different species
32. : Amil Fischer’s ‘Lock-and-key’ theory for enzymes was supported by the fact—
(A) Size of the active site is very small compared to the total protein
(B) Co-enzymes act as the ‘key’ at the active site
(C) Substances similar in structure to that of substrate inhibit enzyme reactions
(D) The enzyme adapts after binding with the substrate and locks it at the active site
33. : All _________ enzymes carry Flavin nucleotides as prosthetic group.
(A) L-Amino acid oxidase
(B) Xanthine oxidase
(C) Cytochrome oxidase
(D) None of these
34. : Which type of enzyme can supply the citric acid cycle with oxaloacetate from pyruvate?
(A) A ligase
(B) A mutase
(C) An isomerase
(D) Both A, B and C
35. : Cooperativity of an allosteric enzyme can be studied by—
(A) Michaelis-Menten equation
(B) Hill Equation
(C) Lineweaver-Burk plot
(D) Both A, B and C
36. : In-vivo control of an enzymatic reaction can be achieved by:
(A) Interconversion between forms with different Km values
(B) Phosphorylation
(C) Proteolytic cleavage of the polypeptides
(D) Both A, B and C
37. : Which is a co-enzyme?
(A) Vitamin
(B) ATP
(C) Ubiquinone
(D) Both A, B and C
38. : Hydrolysis of proteins by protease enzymes would yield amino acids in the form of which of the following?
(A) Racemic mixture of amino acids
(B) D-Amino acids
(C) D, L-Amino acids
(D) L-Amino acids
39. : A number of biochemical assays are linked with enzymatic conversion of NAD/NADH. The reaction velocity in these assays is determined by measuring the change in optical density at:
(A) 550 nm
(B) 340 nm
(C) 290 nm
(D) 210 nm
40. : The Vmax of an enzymatic reaction may be dependent on which of the following?
(A) K of the enzyme
(B) Concentration of the enzyme
(C) Concentration of the competitive inhibitor
(D) Both A, B and C
41. : Which is a hydrogen transferring co-enzyme?
(A) Pyridoxal phosphate
(B) Thiamine pyrophosphate
(C) NADP+
(D) ATP
42. : According to steady state kinetics, which statement is false?
(A) When [S] = Km, half the substrate binding sites are saturated
(B) Km is larger than the dissociation constants for [ES]
(C) Excluding at very low [S], increase in V₁ is less than increase in [S]
(D) V equals [ES] times k3
43. : Mostly the regulatory reactions in a pathway are enzyme limited. Which is true about such reactions?
(A) They are rate limiting
(B) They are exergonic
(C) They are far from equilibrium and irreversible
(D) Both A, B and C
44. : The enzymes ______ are always present in a cell/organism at relatively constant concentrations.
(A) Proenzymes
(B) Constitutive enzymes
(C) Functional enzymes
(D) Facultative enzymes
45. : Which among the following is extracellular?
(A) Glucose-6-Phosphatase
(B) Hexokinase
(C) Pancreatic amylase
(D) Citrate Synthase
46. : Choose the most ideal statement regarding allosteric enzymes:
(A) Often found at the first committed step
(B) Subject to regulation by covalent modification
(C) They are usually multi-subunit systems
(D) Both A, B and C
47. : The isoenzymes are:
(A) Chemically and immunologically different forms of the enzymes
(B) Chemically and immunologically identical forms of the different enzymes
(C) Different enzymes that carry out same reactions
(D) Structurally related enzymes that carry out different reactions
48. : Which enzymes catalyze the binding of two substrates by covalent bonds?
(A) Lyases
(B) Ligases
(C) Synthases
(D) Reductases
49. : Who proposed the induced fit model of enzyme action?
(A) Amil Fischer
(B) Peter Mitchell
(C) Daniel Koshland
(D) Robert Gilbert
50. : In Lineweaver-Burk plot, the Y-intercept represents:
(A) Vmax
(B) 1/Vmax
(C) 1/Km
(D) Km/Vmax
51. : Which statement regarding enzyme kinetics is NOT TRUE?
(A) Value of Km is independent of concentration
(B) Low Km signifies high affinity for the substrate
(C) The V is reached when [ES] concentration is maximal
(D) Enzymes increase the rate of the reaction by enhancing the forward reaction
52. : Which is NOT TRUE regarding enzymes?
(A) They lower the activation energy of the reaction
(B) They change the rate of approach to equilibrium
(C) They can be very selective with respect to substrate
(D) They lower the standard free energy of the reaction
53. : Which is NOT a characteristic of allosteric enzymes?
(A) Feedback inhibition
(B) Greater specificity than non-allosteric enzymes
(C) They can be very selective with respect to substrate
(D) They lower the standard free energy of the reaction