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1. The compound which has the lowest density is (A) Chylomicron (B) β-Lipoprotein (C) α-Lipoprotein (D) pre β-Lipoprotein 2. Non steroidal anti inflammatory drugs, such as aspirin act by inhibiting the activity of the enzyme: (A) Lipoxygenase (B) Cyclooxygenase (C) Phospholipase A 2 (D) Lipoprotein lipase 3. From arachidonate, synthesis of prostag- landins is catalysed by (A) Cyclooxygenase (B) Lipoxygenase (C) Thromboxane synthase (D) Isomerase 4. A Holoenzyme is
(A) Functional unit (B) Apo enzyme (C) Coenzyme (D) All of these
5. Gaucher’s disease is due to the deficiency of the enzyme: (A) α-Fucosidase (B) β-Galactosidase (C) β-Glucosidase (D) Sphingomyelinase 6. Neimann-Pick disease is due to the defi- ciency of the enzyme: (A) Hexosaminidase A and B (B) Ceramidase (C) Ceramide lactosidase (D) Sphingomyelinase
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7. Krabbe’s disease is due to the deficiency of the enzyme: (A) Ceramide lactosidase (B) Ceramidase (C) β-Galactosidase (D) GM1 β-Galactosidase 8. Fabry’s disease is due to the deficiency of the enzyme: (A) Ceramide trihexosidase (B) Galactocerebrosidase (C) Phytanic acid oxidase (D) Sphingomyelinase 9. Farber’s disease is due to the deficiency of the enzyme: (A) α-Galactosidase (B) Ceramidase (C) β-Glucocerebrosidase (D) Arylsulphatase A. 10. A synthetic nucleotide analogue, used in organ transplantation as a suppressor of immunologic rejection of grafts is (A) Theophylline (B) Cytarabine (C) 4-Hydroxypyrazolopyrimidine (D) 6-Mercaptopurine
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11. Example of an extracellular enzyme is (A) Lactate dehydrogenase (B) Cytochrome oxidase (C) Pancreatic lipase (D) Hexokinase 12. Enzymes, which are produced in inactive form in the living cells, are called (A) Papain (B) Lysozymes (C) Apoenzymes (D) Proenzymes 13. An example of ligases is (A) Succinate thiokinase (B) Alanine racemase (C) Fumarase (D) Aldolase 14 An example of lyases is (A) Glutamine synthetase (B) Fumarase (C) Cholinesterase (D) Amylase 15. Activation or inactivation of certain key regulatory enzymes is accomplished by covalent modification of the amino acid: (A) Tyrosine (B) Phenylalanine (C) Lysine (D) Serine 16. The enzyme which can add water to a carbon-carbon double bond or remove water to create a double bond without breaking the bond is (A) Hydratase (B) Hydroxylase (C) Hydrolase (D) Esterase 17. Fischer’s ‘lock and key’ model of the enzyme action implies that (A) The active site is complementary in shape to that of substance only after interaction. (B) The active site is complementary in shape to that of substance (C) Substrates change conformation prior to active site interaction (D) The active site is flexible and adjusts to substrate 18. From the Lineweaver-Burk plot of Michaelis-Menten equation, Km and Vmax can be determined when V is the reaction velocity at substrate concentra- tion S, the X-axis experimental data are expressed as (A) 1/V (B) V (C) 1/S (D) S 19. A sigmoidal plot of substrate concentra- tion ([S]) verses reaction velocity (V) may indicate (A) Michaelis-Menten kinetics (B) Co-operative binding (C) Competitive inhibition (D) Non-competitive inhibition 20. The Km of the enzyme giving the kinetic data as below is (A) –0.50 (B) –0. (C) +0.25 (D) +0. 21. The kinetic effect of purely competitive inhibitor of an enzyme (A) Increases K (^) m without affecting Vmax (B) Decreases Km without affecting Vmax (C) Increases Vmax without affecting Km (D) Decreases Vmax without affecting Km 22. If curve X in the graph (below) represents no inhibition for the reaction of the enzyme with its substrates, the curve representing the competitive inhibition, of the same reaction is (A) A (B) B (C) C (D) D 23. An inducer is absent in the type of enzyme: (A) Allosteric enzyme (B) Constitutive enzyme (C) Co-operative enzyme (D) Isoenzymic enzyme 24. A demonstrable inducer is absent in (A) Allosteric enzyme (B) Constitutive enzyme (C) Inhibited enzyme (D) Co-operative enzyme
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40. Cocarboxylase is (A) Thiamine pyrophosphate (B) Pyridoxal phosphate (C) Biotin (D) CoA 41. A coenzyme containing non aromatic hetero ring is (A) ATP (B) NAD (C) FMN (D) Biotin 42. A coenzyme containing aromatic hetero ring is (A) TPP (B) Lipoic acid (C) Coenzyme Q (D) Biotin 43. Isoenzymes are (A) Chemically, immunologically and electro- phoretically different forms of an enzyme (B) Different forms of an enzyme similar in all properties (C) Catalysing different reactions (D) Having the same quaternary structures like the enzymes 44. Isoenzymes can be characterized by (A) Proteins lacking enzymatic activity that are necessary for the activation of enzymes (B) Proteolytic enzymes activated by hydrolysis (C) Enzymes with identical primary structure (D) Similar enzymes that catalyse different reaction 45. The isoenzymes of LDH (A) Differ only in a single amino acid (B) Differ in catalytic activity (C) Exist in 5 forms depending on M and H monomer contents (D) Occur as monomers 46. The normal value of CPK in serum varies between (A) 4–60 IU/L (B) 60–250 IU/L (C) 4–17 IU/L (D) > 350 IU/L 47. Factors affecting enzyme activity: (A) Concentration (B) pH (C) Temperature (D) All of these 48. The normal serum GOT activity ranges from (A) 3.0–15.0 IU/L (B) 4.0–17.0 IU/L (C) 4.0–60.0 IU/L (D) 0.9–4.0 IU/L 49. The normal GPT activity ranges from (A) 60.0–250.0 IU/L (B) 4.0–17.0 IU/L (C) 3.0–15.0 IU/L (D) 0.1–14.0 IU/L 50. The normal serum acid phosphatase activity ranges from (A) 5.0–13.0 KA units/100 ml (B) 1.0–5.0 KA units/100 ml (C) 13.0–18.0 KA units/100 ml (D) 0.2–0.8 KA units/100 ml 51. The normal serum alkaline phosphatase activity ranges from (A) 1.0–5.0 KA units/100 ml (B) 5.0–13.0 KA units/100 ml (C) 0.8–2.3 KA units/100 ml (D) 13.0–21.0 KA units/100 ml 52. In early stages of myocardial ischemia the most sensitive indicator is the measurement of the activity of (A) CPK (B) SGPT (C) SGOT (D) LDH 53. Serum acid phosphatase level increases in (A) Metastatic carcinoma of prostate (B) Myocardial infarction (C) Wilson’s disease (D) Liver diseases 54. Serum alkaline phosphatase level increases in (A) Hypothyroidism (B) Carcinoma of prostate (C) Hyperparathyroidism (D) Myocardial ischemia 55. Serum lipase level increases in (A) Paget’s disease (B) Gaucher’s disease (C) Acute pancreatitis (D) Diabetes mellitus 56. Serum ferroxidase level decreases in (A) Gaucher’s disease (B) Cirrhosis of liver (C) Acute pancreatitis (D) Wilson’s disease
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57. The isoenzymes LDH 5 is elevated in (A) Myocardial infarction (B) Peptic ulcer (C) Liver disease (D) Infectious diseases 58. On the third day of onset of acute myo- cardial infarction the enzyme elevated is (A) Serum AST (B) Serum CK (C) Serum LDH (D) Serum ALT 59. LDH 1 and LDH 2 are elevated in (A) Myocardial infarction (B) Liver disease (C) Kidney disease (D) Brain disease 60. The CK isoenzymes present in cardiac muscle is (A) BB and MB (B) MM and MB (C) BB only (D) MB only 61. In acute pancreatitis, the enzyme raised in first five days is (A) Serum amylase (B) Serum lactic dehydrogenase (C) Urinary lipase (D) Urinary amylase 62. Acute pancreatitis is characterised by (A) Lack of synthesis of zymogen enzymes (B) Continuous release of zymogen enzymes into the gut (C) Premature activation of zymogen enzymes (D) Inactivation of zymogen enzymes 63. An example of functional plasma enzyme is (A) Lipoprotein lipase (B) Amylase (C) Aminotransferase (D) Lactate dehydrogenase 64. A non-functional plasma enzyme is (A) Psudocholinesterase (B) Lipoprotein lipase (C) Proenzyme of blood coagulation (D) Lipase 65. The pH optima for salivary analyse is (A) 6.6–6.8 (B) 2.0–7. (C) 7.9 (D) 8. 66. The pH optima for pancreatic analyse is (A) 4.0 (B) 7. (C) 7.9 (D) 8. 67. The pH optima for sucrase is (A) 5.0–7.0 (B) 5.8–6. (C) 5.4–6.0 (D) 8. 68. The pH optima for maltase is (A) 1.0–2.0 (B) 5.2–6. (C) 5.8–6.2 (D) 5.4–6. 69. The pH optima for lactase is (A) 1.0-2.0 (B) 5.4–6. (C) 5.0–7.0 (D) 5.8–6. 70. The substrate for amylase is (A) Cane sugar (B) Starch (C) Lactose (D) Ribose 71. The ion which activates salivary amylase activity is (A) Chloride (B) Bicarbonate (C) Sodium (D) Potassium 72. The pancreatic amylase activity is in- creased in the presence of (A) Hydrochloric acid (B) Bile salts (C) Thiocyanate ions (D) Calcium ions 73. A carbohydrate which can not be digest- ed in human gut is (A) Cellulose (B) Starch (C) Glycogen (D) Maltose 74. The sugar absorbed by facilitated diffusion and requiring Na independent transporter is (A) Glucose (B) Fructose (C) Galactose (D) Ribose 75. In the intestine the rate of absorption is highest for (A) Glucose and galactose (B) Fructose and mannose (C) Fructose and pentose (D) Mannose and pentose
ENZYMES 145
90. Phosphofructokinase key enzyme in glycolysis is inhibited by (A) Citrate and ATP (B) AMP (C) ADP (D) TMP 91. One of the enzymes regulating glycolysis is (A) Phosphofructokinase (B) Glyceraldehyde-3-phosphate dehydrogenase (C) Phosphotriose isomerase (D) Phosphohexose isomerase 92. Hexokinase is inhibited in an allosteric manner by (A) Glucose-6-Phosphate (B) Glucose-1-Phosphate (C) Fructose-6-phosphate (D) Fructose-1, 6-biphosphate 93. A reaction which may be considered an isomerisation is (A) Glucose 6-Phosphate fructose 6 phosphate (B) 3-Phosphoglycerate 2-phosphoglycerate (C) 2-phosphoglycerate phosphoenol- pyruvate (D) Pyruvate Lactate 94. The net number of ATP formed per mole of glucose in anaerobic glycolysis is (A) 1 (B) 2 (C) 6 (D) 8 95. Pyruvate dehydrogenase a multienzyme complex is required for the production of (A) Acetyl-CoA (B) Lactate (C) Phosphoenolpyruvate (D) Enolpyruvate 96. Dietary deficiency of thiamin inhibits the activity of the enzyme: (A) Pyruvate kinase (B) Pyruvate dehydrogenase (C) Phosphofructokinase (D) Enolase 97. Pyruvate dehydrogenase activity is inhibited by (A) Mercury (B) Zinc (C) Calcium (D) Sodium 98. In the normal resting state of humans, most of the blood glucose burned as fuel is consumed by (A) Liver (B) Adipose tissue (C) Muscle (D) Brain 99. All the enzymes of glycolysis pathway are found in (A) Extramitochondrial soluble fraction of the cell (B) Mitochondria (C) Nucleus (D) Endoplasmic reticulum 100. Most major metabolic pathways are con- sidered mainly either anabolic or cata- bolic. Which of the following pathway is most correctly considered to be am- phibolic? (A) Citric acid cycle (B) Gluconeogenesis (C) Lipolysis (D) Glycolysis 101. The enzymes of the citric acid cycle are located in (A) Mitochondrial matrix (B) Extramitochondrial soluble fraction of the cell (C) Nucleus (D) Endoplasmic reticulum 102. The initial step of the citric acid cycle is (A) Conversion of pyruvate to acetyl-CoA (B) Condensation of acetyl-CoA with oxaloacetate (C) Conversion of citrate to isocitrate (D) Formation of α -ketoglutarate catalysed by isocitrate dehydrogenase 103. The substance which may be considered to play a catalytic role in citric acid cycle is (A) Oxaloacetate (B) Isocitrate (C) Malate (D) Fumarate 104. An enzyme of the citric acid cycle also found outside the mitochondria is (A) Isocitrate dehydrogenase (B) Citrate synthetase (C) α-Ketoglutarate dehydrogenase (D) Malate dehydrogenase
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105. The reaction catalysed by ααααα -ketoglutarate dehydrogenase in the citric acid cycle requires (A) NAD (B) NADP (C) ADP (D) ATP 106. If all the enzymes, intermediates and cofactors of the citric acid cycle as well as an excess of the starting substrate acetyl- CoA are present and functional in an organelle free solution at the appropriate pH, which of the following factors of the citric acid cycle would prove to be rate limiting? (A) Molecular oxygen (B) Half life of enzyme (C) Turnover of intermediates (D) Reduction of cofactors 107. In TCA cycle, oxalosuccinate is converted to ααααα -ketoglutarate by the enzyme: (A) Fumarase (B) Isocitrate dehydrogenase (C) Aconitase (D) Succinase 108. The enzyme -ketoglutarate dehydrogena- se in the citric acid cycle requires (A) Lipoate (B) Folate (C) Pyridoxine (D) Inositol 109. The example of generation of a high energy phosphate at the substrate level in the citric acid cycle is the reaction: (A) Isocitrate α-Ketoglutarate (B) Succinate α-fumarate (C) Malate α-oxaloacetate (D) Succinyl CoA α-Succinate 110. Fluoroacetate inhibits the reaction of citric acid cycle: (A) Isocitrate α-Ketoglutarate (B) Fumarate α-Malate (C) Citrate α-cis-aconitate (D) Succinate α-fumarate 111. Formation of succinyl-CoA from ααααα -Keto- glutarate is inhibited by (A) Fluoroacetate (B) Arsenite (C) Fluoride (D) Iodoacetate 112. The number of ATP molecules generated for each turn of the citric acid cycle is (A) 8 (B) 12 (C) 24 (D) 38 113. Oxidation of one molecule of glucose yields (A) 12 ATP (B) 24 ATP (C) 38 ATP (D) 38 ATP 114. Which of the following intermediates of metabolism can be both a precursor and a product of glucose? (A) Lactate (B) Pyruvate (C) Alanine (D) Acetyl-CoA 115. Mitochondrial membrane is freely preamble to (A) Pyruvate (B) Malate (C) Oxaloacetate (D) Fumarate 116. The reaction of Kreb’s cycle which does not require cofactor of vitamin B group is (A) Citrate isocitrate (B) α -Ketoglutarate succinate (C) Malate oxaloacetate (D) Succinate fumarate 117. The coenzyme not involved in the formation of acetyl-CoA from pyruvate is (A) TPP (B) Biotin (C) NAD (D) FAD 118. A carrier molecule in the citric acid cycle is (A) Acetyl-CoA (B) Citrate (C) Oxaloacetate (D) Malate 119. A specific inhibitor for succinate dehydro- genase is (A) Arsenine (B) Arsenite (C) Citrate (D) Fluoride
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135. Cori disease (Limit dextrinosis) is caused due to absence of (A) Branching enzyme (B) Debranching enzyme (C) Glycogen synthase (D) Phosphorylase 136. Mc Ardle’s syndrome is characterized by the absence of (A) Liver phosphorylase (B) Muscle phosphorylase (C) Branching enzyme (D) Debranching enzyme 137. Pompe’s disease is caused due to deficiency of (A) Lysosomal α-1→4 and 1→6-glucosidase (B) Glucose-6-phosphatase (C) Glycogen synthase (D) Phosphofructokinase 138. Amylopectinosis is caused due to absence of (A) Debranching enzyme (B) Branching enzyme (C) Acid maltase (D) Glucose-6-phosphatase 139. Her’s disease is characterized by deficien- cy of (A) Muscle phosphorylase (B) Liver phosphorylase (C) Debranching enzyme (D) Glycogen synthase 140. Tarui disease is characterized by the deficiency of the enzyme: (A) Liver phosphorylase (B) Muscle phosphorylase (C) Muscle and erythrocyte phosphofructokinase (D) Lysosomal acid maltase 141. The hexose monophosphate pathway includes the enzyme: (A) Maltase dehydrogenase (B) Hexokinase (C) α-Ketoglutarate dehydrogenase (D) Glucose-6-phosphate dehydrogenase 142. The hydrogen acceptor used in pentose phosphate pathway is (A) NAD (B) NADP (C) FAD (D) FMN 143. The enzymes of the pentose phosphate pathway are found in the (A) Cytosol (B) Mitochondria (C) Nucleus (D) Endoplasmic reticulum 144. In pentose phosphate pathway, D-ribulose- 5-phosphate is converted to D-ribose-5- phosphate by the enzyme: (A) Fumarase (B) Ketoisomerase (C) G-6-PD (D) Epimerase 145. The transketolase enzyme in the pentose phosphate pathway requires the B vitamin. (A) Pantothenic acid (B) Thiamin (C) Riboflavin (D) Nicotinic acid 146. Xylulose-5-phosphate serves as a donar of active glycolaldehyde, the acceptor is (A) Erythrose 4-phosphate (B) Ribose 5-phosphate (C) Glyceraldehyde 3-phosphate (D) Sedoheptulose 7-phosphate 147. Pentose phosphate pathway is of signif- icance because it generates (A) NADPH for reductive synthesis (B) Regenerates glucose 6-phosphate (C) Generates fructose 6-phosphate (D) Forms glyceraldehyde 3-phosphate 148. The pentose phosphate pathway protects erythrocytes against hemolysis by assis- ting the enzyme: (A) Superoxide dismutase (B) Catalase (C) Glutathionic peroxidase (D) Cytochrome oxidase
ENZYMES 149
149. Hemolytic anemia is caused by the deficiency of certain enzymes of the pentose phosphate pathway, the principal enzyme involved is (A) Glucose-6-phosphate dehydrogenase (B) Aldolase (C) Fructose 1, 6-bisphosphatase (D) Phosphohexose isomerase 150. The sites for gluconeogenesis are (A) Liver and kidney (B) Skin and pancreas (C) Lung and brain (D) Intestine and lens of eye 151. An enzyme involved in gluconeogenesis is (A) Pyruvate kinase (B) Pyruvate carboxylase (C) Hexokinase (D) Phosphohexose isomerase 152. The enzyme pyruvate carboxylase is present in (A) Cytosol (B) Mitochondria (C) Nucleus (D) Golgi bodies 153. The enzyme phosphoenolpyruvate carboxykinase catalyses the conversion of oxaloacetate to phosphoenolpyruvate requires (A) ATP (B) ADP (C) AMP (D) GTP 154. The enzyme glucose 6-phosphatase is present in (A) Liver (B) Muscle (C) Adipose tissue (D) Brain 155. In gluconeogensis, an allosteric activator required in the synthesis of oxaloacetate from bicarbonate and pyruvate, which is catalysed by the enzyme pyruvate carboxylase is (A) Acetyl CoA (B) Succinate (C) Isocitrate (D) Citrate 156. The number of ATP molecules required to convert 2 molecules of lactate into glucose in mammalian liver is (A) 2 (B) 4 (C) 5 (D) 6 157. For conjugation with many enogenous and exogenous substances before eli- mination in urine, the uronic acid path- way provides (A) Active glucuronate (B) Gulonate (C) Xylulose (D) Xylitol 158. UDP glucose is converted to UDP glucurronate, a reaction catalysed by UDP glucose dehydrogenase requires (A) NAD +^ (B) FAD (C) NADP (D) FMN 159. Pentosuria is a rare hereditary disease is characterized by increased urinary excretion of (A) L-xylulose (B) Xylitol (C) Xylulose 5-phosphate (D) Ribose 5-phosphate 160. The enzyme involved in essential pentosuria is (A) Reductase (B) Hydroxylase (C) Isomerase (D) Racemase 161. Galactose is synthesized from glucose in (A) Mammary gland (B) Intestine (C) Kidney (D) Adipose tissue 162. Galactose is readily converted to glucose in (A) Liver (B) Intestine (C) Kidney (D) Adipose tissue 163. Galactose 1-phosphate is converted to uridine diphosphate galactose, the reaction is catalysed by the enzyme: (A) Glactokinase (B) Galactose 1-phosphate uridyl transferase (C) Uridine diphospho galactose 4-epimerase (D) UDP glucose pyrophosphorylase 164. The best known cause of galactosemia is the deficiency of (A) Galactose 1-phosphate and uridyl transferase (B) Phosphoglucomutase (C) Galactokinase (D) Lactose synthase
ENZYMES 151
180. The formation of (^) ∆∆∆∆∆^2 -trans-enoyl-CoA from acyl-CoA requires the enzyme: (A) Acyl-CoA synthetase (B) Acyl-CoA dehydrogenase (C) 3-Hydroxy acyl-CoA dehydrogenase (D) Thiolase 181. In βββββ -oxidation 3-ketoacyl-CoA is splitted at the 2, 3 position by the enzyme: (A) Hydratase (B) Dehydrogenase (C) Reducatse (D) Thiolase 182. Fatty acids with odd number of carbon atoms yield acetyl-CoA and a molecule of (A) Succinyl-CoA (B) Propionyl-CoA (C) Malonyl-CoA (D) Acetoacetyl-CoA 183 For each of the first 7-acetyl-CoA molecules formed by ααααα -oxidation of palmitic acid, the yield of high energy phosphates is (A) 12 (B) 24 (C) 30 (D) 35 184. The net gain of ATP/mol of palmitic acid on complete oxidation is (A) 88 (B) 105 (C) 129 (D) 135 185. ωωωωω -oxidation is normally a very minor pathway and is brought by hydroxylase enzymes involving (A) Cytochrome a (B) Cytochrome b (C) Cytochrome c (D) Cytochrome p- 186. ααααα -Oxidation i.e., the removal of one carbon at a time from the carboxyl end of the molecule has been detected in (A) Brain tissue (B) Liver (C) Adipose tissue (D) Intestine 187. In βββββ -oxidation, the coenzyme for acyl-CoA dehydrogenase is (A) FMN (B) NAD (C) NADP (D) FAD 188. The coenzyme involved in dehydrogena- tion of 3-hydroxy acyl-CoA is (A) FAD (B) FMN (C) NAD (D) NADP 189. The concentration of ketone bodies in the blood does not normally exceed (A) 0.2 mmol/L (B) 0.4 mmol/L (C) 1 mmol/L (D) 2 mmol/L 190. In humans under normal conditions loss of ketone bodies via urine is usually less than (A) 1 mg/24 hr (B) 4 mg/24 hr (C) 8 mg/24 hr (D) 10 mg/24 hr 191. The structure which appears to be the only organ to add significant quantities of ketone bodies to the blood is (A) Brain (B) Erythrocytes (C) Liver (D) Skeletal muscle 192. The starting material for ketogenesis is (A) Acyl-CoA (B) Acetyl-CoA (C) Acetoacetyl-CoA (D) Malonyl-CoA 193. Enzymes responsible for ketone body formation are associated mainly with the (A) Mitochondria (B) Endoplasmic reticulum (C) Nucleus (D) Golgi apparatus 194. The synthesis of 3-hydroxy-3-methyl- glutaryl-CoA can occur (A) Only in mitochondria of all mammalian tissues (B) Only in the cytosol of all mammalian tissue (C) In both cytosol and mitochondria (D) In lysosomes 195. In the pathway leading to biosynthesis of acetoacetate from acetyl-CoA in liver, the immediate precursor of aceotacetate is (A) Acetoacetyl-CoA (B) 3-Hydroxybutyryl-CoA (C) 3-Hydroxy-3-methyl-glutaryl-CoA (D) 3-Hydroxybutyrate 196. Ketone bodies serve as a fuel for (A) Extrahepatic tissues (B) Hepatic tissues (C) Erythrocytes (D) Mitochondria
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197. In extra hepatic tissues, one mechanism for utilization of acetoacetate involves (A) Malonyl-CoA (B) Succinyl-CoA (C) Propionyl-CoA (D) Acetyl-CoA 198. Ketosis reflects
(A) Increased hepatic glucose liberation (B) Increased fatty acid oxidation (C) Increased carbohydrate utilisation (D) Incresed gluconeogenesis
199. Ketosis is associated with the disease:
(A) Nephritis (B) Diabetes mellitus (C) Edema (D) Coronary artery diseases
200. The main pathway for denovo synthesis of fatty acids occur in (A) Cytosol (B) Mitochondria (C) Microsomes (D) Nucleus 201. Chain elongation of fatty acids in mammalian liver occurs in (A) Nucleus (B) Ribosomes (C) Lysosomes (D) Microsomes 202. Acetyl-CoA is the principal building block of fatty acids. It is produced within the mitochondria and does not diffuse readily into cytosol. The availability of acetyl CoA involves (A) Carnitine acyl transferase (B) Pyruvate dehydrogenase (C) Citrate lyase (D) Thiolase 203. The synthesis of fatty acids is often termed reductive synthesis. (A) NADP +^ (B) NADH (C) FADH 2 (D) NADPH 204. The protein, which is in fact a multifunc- tional enzyme complex in higher organ- ism is (A) Acetyl transacylase (B) Malonyl transacylase (C) 3-Hydroxy acyl-ACP dehyratase (D) Fatty acid synthase 205. The fatty acid synthase complex catalyses (A) 4 sequential enzymatic steps (B) 6 sequential enzymatic steps (C) 7 sequential enzymatic steps (D) 8 sequential enzymatic steps 206. The main source of reducing equivalents (NADPH) for lipogenesis is (A) Pentose phosphate pathway (B) Citric acid cycle (C) Glycolysis (D) Glycogenolysis 207. In fatty acids synthase of both bacteria and mammals, ACP (acyl carrier protein) contain the vitamin: (A) Thiamin (B) Pyridoxine (C) Riboflavin (D) Pantothenic acid 208. Carboxylation of acetyl-CoA to malonyl- CoA requires the enzyme: (A) Acetyl-CoA carboxylase (B) Pyruvate carboxylase (C) Acetyl transacylase (D) Acyl CoA-synthetase 209. The rate limiting reaction in the lipogenic pathway is (A) Acetyl-CoA carboxylase step (B) Ketoacyl synthase step (C) Ketoacyl reductase step (D) Hydratase step 210. Conversion of fatty acyl-CoA to an acyl- CoA derivative having 2 more carbon atoms involves as acetyl donar: (A) Acetyl-CoA (B) Succinyl-CoA (C) Propionyl-CoA (D) Malonyl-CoA 211. A cofactor required for the conversion of acetyl-CoA to malonyl-CoA in extramito- chondrial fatty acid synthesis is (A) Biotin (B) FMN (C) NAD (D) NADP 212. The glycerol for fatty acid esterification in adipocytes is (A) For the most part, derived from glucose (B) Obtained primarily from phosphorylation of glycerol by glycerol kinase (C) Formed from gluconeogenesis (D) Formed from glycogenolysis
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229. Fatty liver is caused due to accumulation of (A) Fatty acids (B) Cholesterol (C) Phospholipids (D) Triacylglycerol 230. A lipotropic factor is
(A) Choline (B) Palmitic acid (C) Calcium (D) Vitamin C
231. Fatty liver is also caused by
(A) CH 3 Cl (B) CCl (^4) (C) Na 2 SO 4 (D) Riboflavin
232. All the enzymes involved in the synthesis of cholesterol are found in (A) Mitochondria (B) Golgi apparatus (C) Nucleus (D) Endoplasmic reticulum and cytosol 233. The source of all the carbon atoms in cholesterol is (A) Acetyl-CoA (B) Bicarbonate (C) Propionyl-CoA (D) Succinyl-CoA 234. Two molecules of acetyl-CoA condense to form acetoacetyl-CoA catalysed by (A) Thiolase (B) Kinase (C) Reductase (D) Isomerase 235. Acetoacetyl-CoA condenses with one more molecule of acetyl-CoA to form (A) Mevalonate (B) Acetoacetate (C) β-Hydroxybutyrate (D) 3-Hydroxy 3-methyl-glutaryl-CoA 236. HMG-CoA is converted to mevalonate by reduction catalysed by (A) HMG-CoA synthetase (B) HMG-CoA reductase (C) Mevalonate kinase (D) Thiolase 237. For reduction enzyme HMG-CoA reductase requires cofactor: (A) NADPH (B) NADP (C) NAD (D) FAD 238. In the biosynthesis of cholesterol, the step which controls the rate and locus of metabolic regulation is (A) Geranyl pyrophosphate farnesyl pyro- phosphate (B) Squalene → lanosterol (C) HMG CoA → mevalonate (D) Lanosterol → 1, 4-desmethyl lanosterol 239. The cyclisation of squalene in mammals results in the direct formation of the sterol. (A) Cholesterol (B) Lanosterol (C) Sistosterol (D) Zymosterol 240. In the biosynthesis of cholesterol, the rate limiting enzyme is (A) Mevalonate kinase (B) HMG-CoA synthetase (C) HMG-CoA reductase (D) Cis-prenyl transferase 241. Cholesterol by a feed back mechanism inhibits the activity of (A) HMG-CoA synthetase (B) HMG-CoA reductase (C) Thilase (D) Mevalonate kinase 242. The activity of HMG-CoA reductase is inhibited by (A) A fungal inhibitor mevastatin (B) Probucol (C) Nicotinic acid (D) Clofibrate 243. Hypolipidemic drugs reduce serum cholesterol and triacylglycerol. The effect of clofibrate is attributed to (A) Block in absorption from G.I.T. (B) Decrease in secretion of triacylglycerol and cholesterol containing VLDL by liver (C) Block in the reabsorption of bile acids (D) Decreased synthesis of cholesterol 244. In biosynthesis of cholesterol triparanol inhibits the activity of the enzyme: (A) ∆^24 Reductase (B) Oxidosqualene-lanosterol cyclase (C) Isomerase (D) Squalene epoxidase
ENZYMES 155
245. HMG-CoA reductase activity is increased by administration of the hormone: (A) Insulin (B) Glucagon (C) Epinephrine (D) Glucocorticoids 246. The principal sterol excreted in feces is (A) Coprostanol (B) Zymosterol (C) Lanosterol (D) Desmosterol 247. The principal rate limiting step in the biosynthesis of bile acids is at the (A) 7-Hydroxylase reaction (B) 12 α-Hydroxylase reaction (C) Conjugation reaction (D) Deconjugation reaction 248. Hypercholesterolemia is found in (A) Xanthomatosis (B) Thyrotoxicosis (C) Hemolytic jaundice (D) Malabsorption syndrom 249. Hypocholesterolemia is found in (A) Thyrotoxicosis (B) Diabetes mellitus (C) Obstructive jaundice (D) Nephrotic syndrome 250. The major source of extracellular cholesterol for human tissue is (A) Very low density lipoprotein (B) High density lipoprotein (C) Low density lipoprotein (D) Albumin 251. Correct ordering of lipoprotein molecules from lowest to the greater density is (A) LDL, IDL, VLDL, chylomicron (B) Chylomicron, VLDL, IDL, LDL (C) VLDL, IDL, LDL, chylomicron (D) LDL, VLDL, IDL, chylomicron 252. In Hurler’s syndrome, urine shows the presence of (A) Keratan sulphate I (B) Chondroitin sulphate (C) Dermatan sulphate and heparan sulphate (D) Keratan sulphate II 253. Defective enzyme in Hunter’s syndrome is (A) α-L-iduronidase (B) Iduronate sulphatase (C) Arylsulphatase B (D) C-acetyl transferase 254. In Hunter’s syndrome (A) There is progressive corneal opacity (B) Keratan sulphate is excreted in the urine (C) Enzyme defective is arylsulphatase B (D) Hearing loss is perceptive 255. An important feature of Von-Gierke’s disease is (A) Muscle cramps (B) Cardiac failure (C) Hypoglycemia (D) Respiratory alkalosis 256. The affected organ in Mc Ardle’s syndrome is (A) Liver (B) Kidney (C) Liver and Heart (D) Skeletal muscle 257. Refsum’s disease is due to deficiency of the enzyme: (A) Pytantate-α-oxidase (B) Glucocerebrosidase (C) Galactocerebrosidase (D) Ceramide trihexosidase 258. An important finding in Refsum’s disease is (A) Accumulation of ceramide trihexoside in the kidney (B) Accumulation of phytanic acid in the blood and tissues (C) Accumulation of gangliosides in brain and spleen (D) Skin eruptions 259. ααααα -Galactosidase enzyme is defective in (A) Tay-sach’s disease (B) Refsum’s disease (C) Sandhoff’s disease (D) Fabry’s disease 260. The hypothesis to explain enzyme– substrate complex formation: (A) Lock and key model (B) Induced fit theory (C) Proenzyme theory (D) Both (A) and (B)
ENZYMES 157
276. Albinism is due to deficiency of the enzyme: (A) Phenylalanine hydroxylase (B) Tyrosinase (C) p-Hydroxyphenylpyruvic acid oxidase (D) Tyrosine dehydrogenase 277. Neonatal tyrosinemia is due to deficiency of the enzyme: (A) p-Hydroxyphenylpyruvate hydroxylase (B) Fumarylacetoacetate hydrolase (C) Phenylalanine hydroxylase (D) Tyrosine dehydrogenase 278. Which of the following is a substrate- specific enzyme? (A) Hexokinase (B) Thiokinase (C) Lactase (D) Aminopeptidase 279. Coenzymes combine with (A) Proenzymes (B) Apoenzymes (C) Holoenzymes (D) Antienzymes 280. Coenzymes are required in which of the following reactions? (A) Oxidation-reduction (B) Transamination (C) Phosphorylation (D) All of these 281. Which of the following coenzyme takes part in hydrogen transfer reactions? (A) Tetrahydrofolate (B) Coenzyme A (C) Coenzyme Q (D) Biotin 282. Which of the following coenzyme takes part in oxidation-reduction reactions? (A) Pyridoxal phosphate (B) Lipoic acid (C) Thiamin diphosphate (D) None of these 283. In conversion of glucose to glucose-6- phsophate, the coenzyme is (A) Mg ++ (B) ATP (C) Both (A) and (B) (D) None of these 284. A coenzyme required in transamination reactions is (A) Coenzyme A (B) Coenzyme Q (C) Biotin (D) Pyridoxal phosphate 285. Coenzyme A contains a vitamin which is (A) Thiamin (B) Ascorbic acid (C) Pantothenic acid (D) Niacinamide 286. Cobamides contain a vitamin which is (A) Folic acid (B) Ascorbic acid (C) Pantothenic acid (D) Vitamin B (^12) 287. A coenzyme required in carboxylation reactions is (A) Lipoic acid (B) Coenzyme A (C) Biotin (D) All of these 288. Which of the following coenzyme takes part in tissue respiration? (A) Coenzyme Q (B) Coenzyme A (C) NADP (D) Cobamide 289. The enzyme hexokinase is a (A) Hydrolase (B) Oxidoreductase (C) Transferase (D) Ligase 290. Which of the following is a proteolytic enzyme? (A) Pepsin (B) Trypsin (C) Chymotrypsin (D) All of these 291. Enzymes which catalyse binding of two substrates by covalent bonds are known as (A) Lyases (B) Hydrolases (C) Ligases (D) Oxidoreductases 292. The induced fit model of enzyme action was proposed by (A) Fischer (B) Koshland (C) Mitchell (D) Markert 293. Allosteric inhibition is also known as (A) Competitive inhibition (B) Non-competitive inhibition (C) Feedback inhibition (D) None of these
158 MCQs IN BIOCHEMISTRY
294. An allosteric enzyme is generally inhibit- ed by (A) Initial substrate of the pathway (B) Substrate analogues (C) Product of the reaction catalysed by allosteric enzyme (D) Product of the pathway 295. When the velocity of an enzymatic reaction equals Vmax , substrate concentration is (A) Half of K (^) m (B) Equal to K (^) m (C) Twice the K (^) m (D) Far above the K (^) m 296. In Lineweaver-Burk plot, the y-intercept represents (A) Vmax (B) K (^) m (C) K (^) m (D) 1/Km 297. In competitive inhibition, the inhibitor
(A) Competes with the enzyme (B) Irreversibly binds with the enzyme (C) Binds with the substrate (D) Competes with the substrate 298 Competitive inhibitors (A) Decrease the K (^) m (B) Decrease the Vmax (C) Increase the K (^) m (D) Increase the V (^) max
299. Competitive inhibition can be relieved by raising the (A) Enzyme concentration (B) Substrate concentration (C) Inhibitor concentration (D) None of these 300. Physostigmine is a competitive inhibitor of (A) Xanthine oxidase (B) Cholinesterase (C) Carbonic anhydrase (D) Monoamine oxidase 301. Carbonic anhydrase is competitively inhibited by (A) Allopurinol (B) Acetazolamide (C) Aminopterin (D) Neostigmine 302. Serum lactate dehydrogenase rises in (A) Viral hepatitis (B) Myocardial infarction (C) Carcinomatosis (D) All of these 303. Which of the following serum enzyme rises in myocardial infarction: (A) Creatine kinase (B) GOT (C) LDH (D) All of these 304. From the following myocardial infarction, the earliest serum enzyme to rise is (A) Creatine Kinase (B) GOT (C) GPT (D) LDH 305. Proenzymes: (A) Chymotrysinogen (B) Pepsinogen (C) Both (A) and (B) (D) None of these 306. Alkaline phosphatase is present in (A) Liver (B) Bones (C) Placenta (D) All of these 307. Which of the following isoenzyme of lactate dehydrogenase is raised in serum in myocardial infarction: (A) LD 1 (B) LD (^2) (C) LD 1 and LD 2 (D) LD (^5) 308. Enzymes which are always present in an organism are known as (A) Inducible enzymes (B) Constitutive enzymes (C) Functional enzymes (D) Apoenzymes 309. Inactive precursors of enzymes are known as (A) Apoenzymes (B) Coenzymes (C) Proenzymes (D) Holoenzymes 310. Whcih of the following is a proenzyme? (A) Carboxypeptidase (B) Aminopeptidase (C) Chymotrypsin (D) Pepsinogen
