100 Mcqs

1. Enzymes are primarily made of:
a) Carbohydrates
b) Proteins
c) Lipids
d) Nucleic acids

2. What do enzymes do?
a) Provide energy
b) Change the reaction equilibrium
c) Lower activation energy
d) Increase product formation

3. The active site of an enzyme is where:
a) Substrate binds
b) Product forms
c) Denaturation starts
d) Catalysis occurs

4. Enzymes are specific to:
a) Substrate
b) Temperature
c) pH
d) Pressure

5. Meat tenderizer contains which proteolytic enzyme?
a) Lipase
b) Amylase
c) Papain
d) Cellulase

6. Which enzyme hydrolyzes starch?
a) Lipase
b) Amylase
c) Protease
d) Nuclease

7. Catalase breaks down:
a) Sucrose
b) Peptide bonds
c) Hydrogen peroxide
d) DNA

8. Pepsin works in:
a) Mouth
b) Small intestine
c) Stomach (acidic)
d) Blood

9. Optimum pH for pepsin is around:
a) 7
b) 8
c) 2
d) 5

10. Optimum temperature for human enzymes is:
a) 20 °C
b) 30 °C
c) 37 °C
d) 40 °C

11. Enzymes are denatured by:
a) Low substrate
b) Competitive inhibitor
c) High temperature
d) Low enzyme

12. Competitive inhibitors bind to:
a) Allosteric site
b) Active site
c) Substrate
d) Transition state

13. Non‑competitive inhibitors bind to:
a) Allosteric site
b) Active site
c) Substrate
d) Enzyme backbone

14. Enzyme activity increases with:
a) Product formation
b) Substrate concentration (until saturation)
c) Competitive inhibitor
d) Low temperature

15. Vmax is the:
a) Maximum substrate
b) Maximum reaction rate
c) Minimum enzyme activity
d) None

16. Km is a measure of:
a) Reaction rate
b) Substrate concentration at half Vmax
c) pH stability
d) Enzyme size

17. A low Km indicates:
a) High enzyme affinity
b) Low affinity
c) Poor catalysis
d) Low Vmax

18. Which plot is used for enzyme kinetics?
a) Michaelis–Menten
b) Bar graph
c) Lineweaver–Burk
d) Both Michaelis–Menten and Lineweaver–Burk

19. Cofactors are:
a) Proteins
b) Non‑protein helpers
c) Substrates
d) Inhibitors

20. Coenzymes are:
a) Lipids
b) Organic cofactors
c) Metals
d) Polysaccharides

21. Example of a coenzyme is:
a) Heme
b) NAD⁺
c) Zn²⁺
d) Mg²⁺

22. Vitamins often act as:
a) Hormones
b) Coenzymes
c) Enzymes
d) Substrate

23. Allosteric enzymes:
a) Are non‑regulated
b) Can switch between active and inactive forms
c) Always inactive
d) Bind competitively

24. Zymogens are:
a) Active enzymes
b) Inactive precursors
c) Denatured enzymes
d) Synthetic enzymes

25. Trypsinogen activated by:
a) Pepsin
b) Enterokinase
c) Amylase
d) Nuclease

26. Which enzyme synthesizes RNA?
a) DNA polymerase
b) RNA polymerase
c) Ligase
d) Helicase

27. Polymerase enzymes are used in:
a) Digestion
b) DNA replication and transcription
c) Lipid breakdown
d) RNA processing

28. Helicase function is:
a) Joining DNA strands
b) Unwinding DNA helix
c) Replicating DNA
d) Proofreading

29. Restriction enzymes cut:
a) Peptides
b) DNA at specific sequences
c) Lipids
d) Carbohydrates

30. β-galactosidase hydrolyzes:
a) Lipids
b) Proteins
c) Lactose
d) Starch

31. Lipase digests:
a) Starch
b) Lipids
c) Proteins
d) Nucleic acids

32. Urease converts:
a) Urea to glucose
b) Urea to ammonia and CO₂
c) Ammonia to urea
d) Protein to urea

33. Enzyme that links fragments in DNA replication:
a) Polymerase
b) Ligase
c) Helicase
d) Topoisomerase

34. Which enzyme removes RNA primers?
a) DNA ligase
b) Exonuclease
c) Endonuclease
d) Helicase

35. Telomerase is a:
a) Digestive enzyme
b) Reverse transcriptase enzyme
c) DNA ligase subtype
d) Endonuclease

36. Enzyme with RNA and protein is:
a) DNA polymerase
b) Ribozymes (like ribosome)
c) Trypsin
d) Protease

37. Enzyme denaturation is reversible if:
a) Multiple bonds break
b) Primary structure intact
c) Secondary bonds break only
d) Protein oxidized

38. High enzyme concentration causes:
a) Lower Vmax
b) Higher Vmax
c) Lower Km
d) Inhibition

39. Isoenzymes are:
a) Different enzymes catalyzing same reaction
b) Same enzyme in different pH
c) Identical enzymes
d) Inhibitors

40. Feedback inhibition is:
a) Competitive
b) Stimulatory
c) End-product inhibition
d) Non-competitive

41. Enzyme turnover number refers to:
a) Substrate affinity
b) Products formed per time per enzyme molecule
c) Km value
d) Cofactor amount

42. Catalytic efficiency =
a) Vmax × Km
b) kcat / Km
c) kcat × Km
d) Km / kcat

43. Immobilized enzymes are used in:
a) Industrial processes
b) Body only
c) Free in cytoplasm
d) Random reactions

44. Lactase deficiency causes:
a) Protein deficiency
b) Lactose intolerance
c) DNA damage
d) Lipid metabolism issue

45. ACE is an enzyme involved in:
a) DNA replication
b) Blood pressure regulation (Angiotensin‑converting enzyme)
c) Lipid digestion
d) Protein synthesis

46. Carbonic anhydrase speeds up conversion of:
a) CO₂ to glucose
b) CO₂ and H₂O to bicarbonate
c) O₂ transport
d) Protein folding

47. Lysozyme digests:
a) RNA
b) Protein
c) Bacterial cell wall (peptidoglycan)
d) Lipid membrane

48. Enzyme activity measurement unit:
a) Grams
b) Joules
c) International Unit (IU)
d) Moles

49. Temperature coefficient Q₁₀ is:
a) pH effect
b) Rate change for 10° C rise
c) Substrate concentration
d) Enzyme denaturation

50. Michaelis–Menten equation describes relation between:
a) pH and enzyme
b) Reaction rate and substrate concentration
c) Temperature and activity
d) Cofactor and enzyme

51. Transpeptidase is inhibited by:
a) Amoxicillin
b) Streptokinase
c) Penicillin
d) Cholesterol

52. Chymotrypsin acts in:
a) Mouth
b) Small intestine
c) Stomach
d) Esophagus

53. Reverse transcriptase synthesizes:
a) DNA from DNA
b) RNA from RNA
c) DNA from RNA (retroviral)
d) Protein

54. Enzyme poisoning by cyanide blocks:
a) ATP synthase
b) Cytochrome oxidase
c) DNA polymerase
d) RNA polymerase

55. Glutathione reductase uses:
a) ATP
b) NADPH
c) FAD
d) NAD⁺

56. Enzyme localization in cells influences:
a) Protein synthesis only
b) Metabolic pathways separation
c) DNA replication only
d) None

57. Enzyme-substrate complex abbreviation:
a) E‑P
b) E + S
c) ES
d) EP

58. Reaction specificity is:
a) Broad spectrum
b) High substrate specificity
c) Competitive only
d) Non-specific

59. An enzyme inhibitor used clinically is:
a) NADH
b) DNA ligase
c) Viagra (PDE5 inhibitor)
d) Hemoglobin

60. Enzyme-linked immunosorbent assay uses:
a) RNA polymerase
b) Hexokinase
c) Peroxidase or phosphatase labels
d) DNA ligase

61. Which amino acid might play catalytic role in enzyme?
a) Glycine
b) Histidine
c) Leucine
d) Alanine

62. Which metal ion is cofactor for carbonic anhydrase?
a) Na⁺
b) Zn²⁺
c) Fe²⁺
d) Mg²⁺

63. Which enzyme breaks down DNA?
a) Protease
b) Lipase
c) DNase
d) RNase

64. RNase digests:
a) DNA
b) Protein
c) RNA
d) Lipid

65. Enzymes lower activation energy by:
a) Raising free energy
b) Stabilizing transition state
c) Breaking covalent bonds
d) Reducing substrate

66. Isoenzyme levels help diagnose:
a) Diabetes
b) Hypertension
c) Myocardial infarction (e.g., CK-MB)
d) Obesity

67. Enzyme assay measures:
a) Substrate only
b) Product formation or substrate disappearance
c) Temperature
d) Pressure

68. Enzyme inhibition kinetics graph slope increase indicates:
a) Competitive inhibition
b) Non‑competitive
c) No inhibition
d) Irreversible

69. Irreversible inhibitors form:
a) Reversible interactions
b) Covalent bonds that deactivate enzyme
c) Ionic bonds
d) Hydrogen bonds only

70. Zymogen suffix is often:
a) -ase
b) -ogen
c) -ose
d) -ine

71. Enzyme that converts glucose‑6‑phosphate to fructose‑6‑phosphate:
a) Hexokinase
b) Phosphoglucose isomerase
c) Pyruvate kinase
d) Phosphofructokinase

72. Enzyme that provides energy currency in glycolysis:
a) Aldolase
b) Hexokinase
c) Phosphofructokinase
d) Pyruvate kinase

73. Inhibition reversed by increasing substrate concentration indicates:
a) Competitive inhibition
b) Non‑competitive
c) Mixed
d) Allosteric

74. Which vitamin deficiency impairs prolyl hydroxylase in collagen synthesis?
a) Vitamin B6
b) Vitamin C
c) Vitamin K
d) Vitamin D

75. Which enzyme removes supercoils in DNA?
a) Helicase
b) Topoisomerase
c) Ligase
d) Polymerase

76. Phosphatase removes:
a) Amino group
b) Phosphate group
c) Methyl group
d) Acetyl group

77. Kinase adds:
a) Oxygen
b) Phosphate
c) Amino acid
d) Lipid

78. Dehydrogenases transfer:
a) Phosphate
b) Electrons/H‑atoms
c) Acetyl group
d) CO₂

79. Name of enzyme that breaks peptide bonds:
a) Lipase
b) Protease
c) Isoenzyme
d) Kinase

80. Exopeptidase cleaves:
a) Middle peptide bonds
b) Terminal amino acids
c) Disulfide bonds
d) Covalent backbone

81. Endopeptidase cleaves:
a) Internal peptide bonds within chain
b) Terminal amino acids
c) Polysaccharides
d) Lipids

82. Enzyme specificity can be:
a) Group or General
b) Absolute, group, or linkage type
c) Substrate only
d) Temperature only

83. Which enzyme catalyzes bond rotation in DNA?
a) Ligase
b) Topoisomerase
c) Helicase
d) Polymerase

84. Proteases operate in:
a) Cytoplasm only
b) Lysosomes and extracellular digestion
c) Nucleus only
d) Mitochondria only

85. Enzyme turnover depends on:
a) Enzyme size
b) Catalytic rate and enzyme amount
c) Substrate type alone
d) Temperature only

86. In enzyme nomenclature, names often end with:
a) -ogen
b) -ose
c) -ase
d) -ine

87. Allosteric effectors bind:
a) Active site
b) Regulatory site
c) Substrate
d) Product

88. Ribozyme activity is due to:
a) Protein subunit
b) RNA catalytic core
c) Lipid molecule
d) Metal ion only

89. Enzyme activity unit µmol/min measures:
a) Mass substrate
b) µmoles substrate converted per minute
c) ATP generation
d) Binding affinity

90. Which enzyme removes methyl marks from DNA?
a) DNA polymerase
b) DNA demethylase
c) Histone acetyltransferase
d) Ligase

91. Enzyme-linked receptors include:
a) Ion channels
b) Tyrosine kinases (e.g., insulin receptor)
c) G-protein only
d) Lipase receptors

92. What is the function of peroxidases in plants?
a) DNA repair
b) Detoxify H₂O₂
c) Synthesize cellulose
d) Photosynthesis

93. ATPase is an enzyme that hydrolyzes:
a) Glucose
b) ATP
c) DNA
d) Protein

94. Enzymes also function as:
a) Structural proteins
b) Lipids
c) Biological catalysts
d) Genetic material

95. Enzyme solubility is affected by:
a) Substrate conc. only
b) pH and temperature
c) Product type
d) Cofactor only

96. Fumarase catalyzes conversion in:
a) Glycolysis
b) Calvin cycle
c) TCA cycle (fumarate to malate)
d) Electron transport chain

97. Which enzyme allows bacteria to spore formation?
a) Protease
b) Dipicolinate synthase
c) Lipase
d) Amylase

98. Enzymes found in peroxisomes include:
a) Lipase
b) Catalase
c) Amylase
d) DNA polymerase

99. Enzyme kinetics can be influenced by:
a) Substrate only
b) pH, temperature, substrate, inhibitors
c) Cofactor only
d) Solvent only

100. Common model enzyme in labs is:
a) Pepsin
b) Amylase
c) Catalase
d) Trypsin