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pharmacyTopic wise MCQs

Biochemistry ( Part- 4 ) MCQs with Answers


51. Histamine is formed from histidine by the enzyme histidine decarboxylase in the presence of
(C) HS-CoA (D) B6-PO4

52. Infantile convulsions due to lesser formation of gamma amino butyric acid from glutamic acid is seen in the deficiency of
(A) Glutamate-dehydrogenase
(B) Pyridoxine
(C) Folic acid
(D) Thiamin

53. Which of the following amino acids produce a vasoconstrictor on decarboxylation?
(A) Histidine
(B) Tyrosine
(C) Threonine
(D) Arginine

54. The degradation of RNA by pancreatic ribonuclease produces
(A) Nucleoside 2-Phosphates
(B) Nucleoside 5′-phosphates
(C) Oligonucleosides
(D) Nucleoside 3′-phosphate and oligonucleotide

55. Intestinal nucleosidases act on nucleosides and produce
(A) Purine base only
(B) Phosphate only
(C) Sugar only
(D) Purine or pyrimidine bases and sugars

56. In purine biosynthesis carbon atoms at 4 and 5 position and N at 7 position are contributed by
(A) Glycine
(B) Glutamine
(C) Alanine
(D) Threonine

57. N10-formyl and N5N10-methenyl tetrahydrofolate contributes purine carbon atoms at position
(A) 4 and 6
(B) 4 and 5
(C) 5 and 6
(D) 2 and 8

58. In purine nucleus nitrogen atom at 1 position is derived from
(A) Aspartate (B) Glutamate
(C) Glycine (D) Alanine

59. The key substance in the synthesis of purine, phosphoribosyl pyrophosphate is formed by
(A) α-D-ribose 5-phosphate
(B) 5-phospho β-D-ribosylamine
(C) D-ribose
(D) Deoxyribose

60. In purine biosynthesis ring closure in the molecule formyl glycinamide ribosyl-5- phosphate requires the cofactors:
(D) ATP and Mg++

61. Ring closure of formimidoimidazole carboxamide ribosyl-5-phosphate yields the first purine nucleotide:

62. The cofactors required for synthesis of adenylosuccinate are
(A) ATP, Mg++
(C) GTP, Mg++

63. 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

64. Phosphorylation of adenosine to AMP is catalysed by
(A) Adenosine kinase
(B) Deoxycytidine kinase
(C) Adenylosuccinase
(D) Adenylosuccinate synthetase

65. The major determinant of the overall rate of denovo purine nucleotide biosynthesis is the concentration of
(A) 5-phosphoribosyl 1-pyrophosphate
(B) 5-phospho β-D-ribosylamine
(C) Glycinamide ribosyl-5-phosphate
(D) Formylglycinamide ribosyl-5-phosphate

66. An enzyme which acts as allosteric regulator and sensitive to both phosphate concentration and to the purine nucleotides is
(A) PRPP synthetase
(B) PRPP glutamyl midotransferase
(C) HGPR Tase
(D) Formyl transferase

67. PRPP glutamyl amidotransferase, the first enzyme uniquely committed to purine synthesis is feedback inhibited by

68. Conversion of formylglycinamide ribosyl- 5-phosphate to formyl-glycinamide ribosyl-5- phosphate is inhibited by
(A) Azaserine
(B) Diazonorleucine
(C) 6-Mercaptopurine
(D) Mycophenolic acid

69. in the biosynthesis of purine nucleotides The AMP feedback regulates
(A) Adenylosuccinase
(B) Adenylosuccinate synthetase
(C) IMP dehydrogenase
(D) HGPR Tase

70. 6-Mercapto purine inhibits the conversion Of
(B) Ribose 5 phosphate → PRPP
(C) PRPP → 5-phospho →β -D-ribosylamine
(D) Glycinamide ribosyl 5-phosphate → formylglycinamide ribosyl-5-phosphate

71. Purine biosynthesis is inhibited by
(A) Aminopterin
(B) Tetracyclin
(C) Methotrexate
(D) Chloramphenicol

72. Pyrimidine and purine nucleoside biosynthesis share a common precursor:
(A) PRPP (B) Glycine
(C) Fumarate (D) Alanine

73. Pyrimidine biosynthesis begins with the Formation from glutamine, ATP and CO2, Of
(A) Carbamoyl aspartate
(B) Orotate
(C) Carbamoyl phosphate
(D) Dihydroorotate

74. The two nitrogen of the pyrimidine ring are contributed by
(A) Ammonia and glycine
(B) Asparate and carbamoyl phosphate
(C) Glutamine and ammonia
(D) Aspartate and ammonia

75. A cofactor in the conversion of dihydroorotate to orotic acid, catalysed by theenzyme dihydroorotate dehydrogenase is

76. The first true pyrimidine ribonucleotide Synthesized is

77. UDP and UTP are formed by phosphorylation from

78. Reduction of ribonucleotide diphosphates (NDPs) to their corresponding deoxy ribonucleotide diphosphates (dNDPs) involves

79. Conversion of deoxyuridine monophosphate to thymidine monophosphate is Catalysed by the enzyme:
(A) Ribonucleotide reductase
(B) Thymidylate synthetase
(C) CTP synthetase
(D) Orotidylic acid decarboxylase

80. d-UMP is converted to TMP by
(A) Methylation
(B) Decarboxylation
(C) Reduction
(D) Deamination

81. UTP is converted to CTP by
(A) Methylation
(B) Isomerisation
(C) Amination
(D) Reduction

82. 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

83. A substrate for enzymes of pyrimidine nucleotide biosynthesis is
(A) Allopurinol
(B) Tetracylin
(C) Chloramphenicol
(D) Puromycin

84. An enzyme of pyrimidine nucleotide biosynthesis sensitive to allosteric regulation is
(A) Aspartate transcarbamoylase
(B) Dihydroorotase
(C) Dihydroorotate dehydrogenase
(D) Orotidylic acid decarboxylase

85 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

86. The enzyme aspartate transcarbamoylase of pyrimidine biosynthesis is inhibited by

87. In humans end product of purine catabolism is
(A) Uric acid (B) Urea
(C) Allantoin (D) Xanthine

88. in human’s purine are catabolised to uric acid due to lack of the enzyme:
(A) Urease
(B) Uricase
(C) Xanthine oxidase
(D) Guanase

89. in mammals other than higher primates Uric acid is converted by
(A) Oxidation to allantoin
(B) Reduction to ammonia
(C) Hydrolysis to ammonia
(D) Hydrolysis to allantoin

90. The correct sequence of the reactions of catabolism of adenosine to uric acid is
(A) Adenosine→hypoxanthine→xanthine→ uric acid
(B) Adenosine→xanthine→inosine→uric acid
(C) Adenosine→inosine→hypoxanthine→ xanthine uric acid
(D) Adenosine→xanthine→inosine→hypoxanthine uric acid

91. Gout is a metabolic disorder of catabolism of
(A) Pyrimidine
(B) Purine
(C) Alanine
(D) Phenylalanine

92. Gout is characterized by increased plasma levels of
(A) Urea (B) Uric acid
(C) Creatine (D) Creatinine

93. Lesch-Nyhan syndrome, the sex linked recessive disorder is due to the lack of the enzyme:
(A) Hypoxanthine-guanine phosphoribosyl Transferse
(B) Xanthine oxidase
(C) Adenine phosphoribosyl transferase
(D) Adenosine Deaminase

94. Lesch-Nyhan syndrome, the sex linked, recessive absence of HGPRTase, may lead to
(A) Compulsive self-destructive behaviour with elevated levels of urate in serum
(B) Hypouricemia due to liver damage
(C) Failure to thrive and megaloblastic anemia
(D) Protein intolerance and hepatic encephalopathy

95. The major catabolic product of pyrimidines in human is
(A) β-Alanine
(B) Urea
(C) Uric acid
(D) Guanine

96. 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

97. Orotic aciduria type II reflects the deficiency of the enzyme:
(A) Orotate phosphoribosyl transferase
(B) Orotidylate decarboxylase
(C) Dihydroorotase
(D) Dihydroorotate dehydrogenase

98. An autosomal recessive disorder, xanthinuria is due to deficiency of the enzymes:
(A) Adenosine deaminase
(B) Xanthine oxidase
(C) HGPRTase
(D) Transaminase

99. Enzymic deficiency in βββ-aminoisobutyric aciduria is
(A) Adenosine deaminase
(B) Xanthine oxidase
(C) Orotidylate decarboxylase
(D) Transaminase

100. Polysomes lack in

(B) mRNA
(C) rRNA

(D) tRNA