51. Bacteria living in hot springs may have enzymes with an optimum of:
Answer: C. 70 degrees or higher
Biology Class 11 Unit 3: Enzymes MCQs
146 multiple choice questions with the correct answer for each. Tap an option to check yourself, or switch on "Show all answers". This is page 2 of 3.
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52. At or below freezing point enzymes are:
Answer: C. inactivated but not denatured
53. Enzymes inactivated by cold regain activity when:
Answer: B. temperature is restored to a higher level
54. Most enzymes have optimum pH in the range of:
Answer: C. 6 to 8
55. Pepsin is most active at:
Answer: C. pH 2
56. Trypsin shows maximum activity at:
Answer: D. pH 8
57. Papain from green papaya latex is a:
Answer: B. cysteine protease active in both acidic and alkaline media
58. The optimum temperature of papain is about:
Answer: C. 65 degrees
59. The effect of pH on enzyme activity is due to a change in:
Answer: B. the charges on amino acid side chains
60. When substrate is in excess, the rate of reaction is directly proportional to:
Answer: B. enzyme concentration
61. If an enzyme solution is saturated with substrate, to obtain faster product formation the best method is to:
Answer: B. add more enzyme
62. Enzyme inhibition is the phenomenon in which:
Answer: B. an enzyme fails to catalyse a reaction due to binding of inhibitor
63. A competitive inhibitor:
Answer: B. competes with the substrate for the active site
64. A competitive inhibitor is usually structurally:
Answer: B. similar to the substrate
65. Malonate competitively inhibits:
Answer: B. succinate dehydrogenase
66. Succinate dehydrogenase converts succinate to:
Answer: B. fumarate
67. Competitive inhibition can be overcome by:
Answer: B. increasing substrate concentration
68. Competitive inhibition is usually:
Answer: B. reversible
69. Sulphonamides act as:
Answer: B. competitive inhibitors used against bacterial infection
70. In non-competitive inhibition the inhibitor binds to:
Answer: C. the allosteric site
71. Increasing substrate concentration has no effect on:
Answer: B. non-competitive inhibition
72. Feedback inhibition is an example of:
Answer: C. reversible non-competitive inhibition
73. In feedback inhibition the enzyme is inhibited by its own:
Answer: B. end product
74. In the aspartate to threonine pathway, excess threonine binds to the allosteric site of:
Answer: B. enzyme 1
75. Cyanides kill organisms by inhibiting:
Answer: C. cytochrome oxidase
76. Cyanides act by combining with:
Answer: B. iron in the prosthetic group
77. Ions of mercury, silver and copper combine with:
Answer: B. thiol (-SH) groups of the enzyme
78. Heavy metals denature enzymes by breaking:
Answer: B. disulphide bridges
79. Penicillin kills bacteria by blocking:
Answer: B. the active site of an enzyme unique to bacteria
80. Which is a non-competitive inhibitor?
Answer: C. Cyanide
81. DFP (nerve gas) is a:
Answer: B. non-competitive inhibitor
82. The international classification of enzymes by reaction type divides enzymes into how many groups?
Answer: C. Six
83. The IUB system of enzyme nomenclature was given in:
Answer: C. 1961
84. Enzymes catalysing oxidation and reduction are:
Answer: B. oxidoreductases
85. Cytochrome oxidase belongs to:
Answer: C. oxidoreductases
86. Hexokinase transferring a phosphate group from ATP to glucose is a:
Answer: B. transferase
87. Enzymes breaking down large molecules by adding water are:
Answer: C. hydrolases
88. Pepsin, renin and trypsin belong to:
Answer: B. hydrolases
89. Enzymes that remove groups without hydrolysis, e.g. histidine decarboxylase, are:
Answer: B. lyases
90. Histidine decarboxylase produces carbon dioxide and:
Answer: B. histamine
91. Enzymes which bring intramolecular rearrangement are:
Answer: C. isomerases
92. Phosphohexose isomerase changes glucose 6-phosphate to:
Answer: B. fructose 6-phosphate
93. Enzymes joining two molecules together using energy from ATP are:
Answer: D. ligases (synthetases)
94. DNA ligase belongs to the class:
Answer: C. ligases
95. Which is a protease?
Answer: B. Erypsin
96. Amylase digests:
Answer: C. starch or glycogen into maltose
97. Cellulase digests cellulose into:
Answer: C. cellobiose
98. Maltase digests maltose into:
Answer: C. glucose
99. Sucrase digests sucrose into:
Answer: C. glucose and fructose
100. Lactase digests lactose into:
Answer: C. galactose and glucose
About Biology Class 11 Unit 3 MCQs (Federal Board)
These 146 Biology MCQs cover Class 11 Unit 3: Enzymes of the Federal Board (FBISE) HSSC-I (1st Year / Class 11) syllabus. They are SLO-based MCQs as per the new pattern for FBISE exams. Each question has four options and the correct answer is shown, so you can practise for the annual examination and find the topics you still need to revise. The questions are split over 3 pages of 50. Use the Print button to save this chapter as a PDF.