Description : Methotrexate blocks the synthesis of thymidine monophosphate by inhibiting the activity of the enzyme: (A) Dihydrofolate reductase (B) Orotate phosphoribosyl transferase (C) Ribonucleotide reductase (D) Dihydroorotase
Last Answer : Answer : A
Description : Conversion of uridine diphosphate into deoxyuridine diphosphate requires all the following except (A) Ribonucleotide reductase (B) Thioredoxin (C) Tetrahydrobiopterin (D) NADPH
Last Answer : Answer : C
Description : An enzyme of pyrimidine nucleotide biosynthesis sensitive to allosteric regulation is (A) Aspartate transcarbamoylase (B) Dihydroorotase (C) Dihydroorotate dehydrogenase (D) Orotidylic acid decarboxylase
Description : Conversion of uroporphyrinogen III to coprophyrinogen III is catalysed by the enzyme.: (A) Uroporphyrinogen decarboxylase (B) Coproporphyrinogen oxidase (C) Protoporphyrinogen oxidase (D) Ferrochelatase
Description : Conversion of fructose to sorbitol is catalysed by the enzyme: (A) Sorbitol dehydrogenase (B) Aldose reductase (C) Fructokinase (D) Hexokinase
Description : Cancer cells may become resistant to amethopterin by (A) Developing mechanisms to destroy amethopterin (B) Amplification of dihydrofolate reducatse gene (C) Mutation in the dihydrofolate reductase ... is no longer inhibited by amethopterin (D) Developing alternate pathway of thymidylate synthesis
Last Answer : Answer : B
Description : HMG-CoA is converted to mevalonate by reduction catalysed by (A) HMG-CoA synthetase (B) HMG-CoA reductase (C) Mevalonate kinase (D) Thiolase
Description : Conversion of inosine monophosphate to xanthine monophosphate is catalysed by (A) IMP dehydrogenase (B) Formyl transferase (C) Xanthine-guanine phosphoribosyl transferase (D) Adenine phosphoribosyl transferase
Description : An enzyme of pyrimidine nucleotides biosynthesis regulated at the genetic level by apparently coordinate repression and derepression is (A) Carbamoyl phosphate synthetase (B) Dihydroorotate dehydrogenase (C) Thymidine kinase (D) Deoxycytidine kinase
Description : Amplification of dihydrofolate reductase gene may be brought about by (A) High concentrations of folic acid (B) Deficiency of folic acid (C) Low concentration of thymidylate (D) Amethopterin
Last Answer : Answer : D
Description : The first true pyrimidine ribonucleotide synthesized is (A) UMP (B) UDP (C) TMP (D) CTP
Description : Synthesis of phosphatidylinositol by transfer of inositol to CDP diacylglycerol is catalysed by the enzyme: (A) CTP phosphatidate cytidyl transferase (B) Phosphatidate phosphohydrolase (C) CDP-diacylglycerol inositol transferase (D) Choline kinase
Description : All the following statements about charging of tRNA are correct except (A) It is catalysed by amino acyl tRNA synthetase (B) ATP is converted into ADP and Pi in this reaction (C) The enzyme recognizes the tRNA and the amino acid (D) There is a separate enzyme for each tRNA
Description : Both Acyl carrier protein (ACP) of fatty acid synthetase and coenzyme (CoA) are (A) Contain reactive phosphorylated (B) Contain thymidine (C) Contain phosphopantetheine reactive groups (D) Contain cystine reactive groups
Description : 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
Description : An enzyme required for the synthesis of ketone bodies as well as cholesterol is (A) Acetyl CoA carboxylase (B) HMG CoA synthetase (C) HMG CoA reductase (D) HMG CoA lyase
Description : Riboflavin is a coenzyme in the reaction catalysed by the enzyme (A) Acyl CoA synthetase (B) Acyl CoA dehydrogenase (C) β-Hydroxy acyl CoA (D) Enoyl CoA dehydrogenase
Description : Transfer of the carbamoyl moiety of carbamoyl phosphate to ornithine is catalysed by a liver mitochondrial enzyme: (A) Carbamoyl phosphate synthetase (B) Ornithine transcarbamoylase (C) N-acetyl glutamate synthetase (D) N-acetyl glutamate hydrolase
Description : A cofactor in the conversion of dihydroorotate to orotic acid, catalysed by the enzyme dihydroorotate dehydrogenase is (A) FAD (B) FMN (C) NAD (D) NADP
Description : Trimethoprim inhibits bacteria without affecting mammalian cells because: A. It does not penetrate mammalian cells B. It has high affinity for bacterial but low affinity for mammalian dihydrofolate ... bacterial folate synthetase as well as dihydrofolate reductase enzymes D. All of the above
Last Answer : B. It has high affinity for bacterial but low affinity for mammalian dihydrofolate reductase enzyme
Description : The enzyme catalyzing conversion of androstenedione to testosterone is a (A) Oxygenase (B) Dehydrogenase (C) Isomerase (D) Decarboxylase
Description : Cytosolic carbamoyl phosphate synthetase is inhibited by (A) UTP (B) CTP (C) PRPP (D) TMP
Description : CTP synthetase forms CTP from (A) CDP and inorganic phosphate (B) CDP and ATP (C) UTP and glutamine (D) UTP and glutamate
Description : The rate limiting step in catecholamine synthesis is catalysed by (A) Phenylalanine hydroxylase (B) Tyrosine hydroxylase (C) Dopa decarboxylase (D) Phenylethanolamine N-methyl transferase
Description : The decarboxylation reaction in HMP shunt is catalysed by (A) Gluconolactone hydrolase (B) 6-Phosphogluconate dehydrogenase (C) 6-Phosphogluconate decarboxylase (D) Transaldolase
Description : Orotic aciduria type I reflects the deficiency of enzymes: (A) Orotate phosphoribosyl transferase and orotidylate decarboxylase (B) Dihydroorotate dehydrogenase (C) Dihydroorotase (D) Carbamoyl phosphate synthetase
Description : Two molecules of acetyl-CoA condense to form acetoacetyl-CoA catalysed by (A) Thiolase (B) Kinase (C) Reductase (D) Isomerase
Description : The metabolic reaction requiring vitamin B12 but not folate is: A. Conversion of malonic acid to succinic acid B. Conversion of homocysteine to methionine C. Conversion of serine to glycine D. Thymidylate synthesis
Last Answer : A. Conversion of malonic acid to succinic acid
Description : Cholesterol by a feed back mechanism inhibits the activity of (A) HMG-CoA synthetase (B) HMG-CoA reductase (C) Thilase (D) Mevalonate kinase
Description : The rage limiting step cholesterol biosynthesis is (A) Squalene synthetase (B) Mevalonate kinase (C) HMG CoA synthetase (D) HMG CoA reductase
Description : Lovastatin is a (A) Competitive inhibitor of acetyl CoA carboxylase (B) Competitive inhibitor of HMG CoA synthetase (C) Non-competitive inhibitor of HMG CoA reductase (D) Competitive inhibitor of HMG CoA reductase
Description : The first reaction unique to purine nucleotide synthesis is catalysed by (A) PRPP synthetase (B) PRPP glutamyl amido transferase (C) Phosphoribosyl glycinamide synthetase (D) Formyl transferase
Description : Phosphorylation of adenosine to AMP is catalysed by (A) Adenosine kinase (B) Deoxycytidine kinase (C) Adenylosuccinase (D) Adenylosuccinate synthetase
Description : Conversion of testosterone to dihydrotestosterone by the enzyme 5α-reductase is required for the following actions except: A. Formation of male external genitalia in the foetus B. Prostatic hypertrophy in elderly males C. Pubertal changes in the male adolescent D. Spermatogenesis
Last Answer : D. Spermatogenesis
Description : An enzyme involved in catabolism of catecholamines is (A) Dopa decarboxylase (B) Aromatic amino acid decarboxylase (C) Monoamine oxidase (D) Catechol oxidas
Description : The α-ketoacid is decarboxylated by H2O2 forming a carboxylic acid with one carbon atom less in the absence of the enzyme: (A) Catalase (B) Decarboxylase (C) Deaminase (D) Phosphatase
Description : 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
Description : The hexose monophosphate pathway includes the enzyme: (A) Maltase dehydrogenase (B) Hexokinase (C) α-Ketoglutarate dehydrogenase (D) Glucose-6-phosphate dehydrogenase
Description : The following enzyme is required for the hexose monophosphate shunt pathway: (A) Glucose-6-phosphatase (B) Phosphorylase (C) Aldolase (D) Glucose-6-phosphate dehydrogenase
Last Answer : D
Description : Which is the key enzyme of hexose monophosphate shunt pathway?
Last Answer : Glucose-6-phosphate dehydrogenase.
Description : In the biosynthesis of c-DNA, the joining enzyme ligase requires (A) GTP (B) ATP (C) CTP (D) UTP
Description : The enzyme aspartate transcarbamoylase of pyrimidine biosynthesis is inhibited by (A) ATP (B) ADP (C) AMP (D) CTP
Description : 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
Description : The following enzyme of urea cycle is present in cytosol: (A) Argininosuccinic acid synthetase (B) Argininosuccinase (C) Arginase (D) All of these
Description : Orotic aciduria type II reflects the deficiency of the enzyme: (A) Orotate phosphoribosyl transferase (B) Orotidylate decarboxylase (C) Dihydroorotase (D) Dihydroorotate dehydrogenase
Description : Histamine is formed from histidine by the enzyme histidine decarboxylase in the presence of (A) NAD (B) FMN (C) HS-CoA (D) B6-PO4
Description : In the synthetic pathway of epinephrine, disulfiram (antabuse) inhibits the enzyme: (A) Tyrosine hydroxylase (B) Dopamine β-hydroxylase (C) DOPA decarboxylase (D) N-methyl transferase
Description : For Catecholamine biosynthesis the rate limiting enzyme is (A) DOPA decarboxylase (B) DOPAMINE β-hydroxylase (C) Tyrosine hydroxylase (D) Phenylalanine hydroxylase
Description : The enzyme involved in variegate porphyria is (A) Protoporphyrinogen oxidase (B) Coproporphyrinogen oxidase (C) Uroporphyrinogen decarboxylase (D) ALA decarboxylase
Description : Biotin is a coenzyme of the enzyme (A) Carboxylase (B) Hydroxylase (C) Decarboxylase (D) Deaminase