Which enzyme facilitates the creation of histamine from histidine, given the presence of specific molecules?
Answer
(D)
B-PO4
2
A decreased production of gamma-aminobutyric acid from glutamic acid, potentially leading to infantile convulsions, is linked to a deficiency of which substance?
Answer
(B)
Pyridoxine
3
Which amino acid, upon removal of a carboxyl group, leads to the production of a compound that narrows blood vessels?
Answer
(B)
Tyrosine
4
What are the products of the breakdown of RNA by pancreatic ribonuclease?
Answer
(D)
Nucleoside 3'-phosphate and oligonucleotide
5
What are the resulting products when intestinal nucleosidases interact with nucleosides?
Answer
(D)
Purine or pyrimidine bases and sugars
6
In the creation of purines, which of the following provides the carbon atoms for positions 4 and 5, and the nitrogen atom at position 7?
Answer
(A)
Glycine
7
At which positions on the purine structure do N¹º-formyl and N5N10-methenyl tetrahydrofolate contribute carbon atoms?
Answer
(D)
2 and 8
8
From which molecule does the nitrogen atom at position 1 in the purine nucleus originate?
Answer
(A)
Aspartate
9
The crucial component for purine synthesis, phosphoribosyl pyrophosphate, is generated from which substance?
Answer
(A)
a-D-ribose 5-phosphate
10
What combination of factors is essential for the ring closure step in the creation of formyl glycinamide ribosyl-5-phosphate during purine synthesis?
Answer
(D)
ATP and Mg++
11
What is the product of the ring closure reaction involving formimidoimidazole carboxamide ribosyl-5-phosphate, representing the initial purine nucleotide?
Answer
(B)
IMP
12
Which cofactors are essential for the synthesis of adenylosuccinate?
Answer
(C)
GTP, Mg++
13
Which enzyme facilitates the transformation of inosine monophosphate into xanthine monophosphate?
Answer
(A)
IMP dehydrogenase
14
What enzyme is responsible for catalyzing the phosphorylation of adenosine, resulting in AMP?
Answer
(A)
Adenosine kinase
15
What is the primary factor determining the overall rate of de novo purine nucleotide biosynthesis, considering its concentration?
Answer
(A)
5-phosphoribosyl 1-pyrophosphate
16
Which enzyme functions as an allosteric regulator, showing sensitivity to both phosphate concentration and purine nucleotides?
Answer
(A)
PRPP synthetase
17
PRPP glutamyl amidotransferase, the initial committed enzyme in purine synthesis, is subject to feedback inhibition by which of the following?
Answer
(A)
AMP
18
The conversion of formylglycinamide ribosyl-5-phosphate to formyl-glycinamide ribosyl-5-phosphate is inhibited by which substance?
Answer
(A)
Azaserine
19
In the purine nucleotide biosynthesis pathway, which enzyme is regulated by feedback inhibition from AMP?
Answer
(B)
Adenylosuccinate synthetase
20
The action of 6-Mercapto purine results in the inhibition of the following conversion:
Answer
(A)
IMP→XMP
21
Which substance is known to block purine synthesis?
Answer
(A)
Aminopterin
22
What compound serves as a shared starting material for the creation of both pyrimidine and purine nucleosides?
Answer
(A)
PRPP
23
The beginning of pyrimidine synthesis involves the creation of which compound from glutamine, ATP, and CO₂?
Answer
(C)
Carbamoyl phosphate
24
From which two sources do the nitrogen atoms in a pyrimidine ring originate?
Answer
(B)
Asparate and carbamoyl phosphate
25
Which molecule acts as an assistant in the dihydroorotate dehydrogenase-catalyzed transformation of dihydroorotate into orotic acid?
Answer
(C)
NAD
26
What is the initial pyrimidine ribonucleotide produced during synthesis?
Answer
(A)
UMP
27
What molecule is the source of the phosphate groups used to convert UDP and UTP?
Answer
(C)
ATP
28
The transformation of ribonucleotide diphosphates (NDPs) into their corresponding deoxy forms (dNDPs) requires which of the following?
Answer
(D)
NADPH
29
The enzyme that carries out the conversion of deoxyuridine monophosphate to thymidine monophosphate is:
Answer
(B)
Thymidylate synthetase
30
What process is responsible for converting d-UMP to TMP?
Answer
(A)
Methylation
31
Which process transforms UTP into CTP?
Answer
(C)
Amination
32
Which enzyme's activity is inhibited by Methotrexate, thus blocking thymidine monophosphate synthesis?
Answer
(A)
Dihydrofolate reductase
33
Which substance serves as a starting material for the enzymes involved in pyrimidine nucleotide creation?
Answer
(A)
Allopurinol
34
Which enzyme in pyrimidine nucleotide biosynthesis is known for its allosteric regulation?
Answer
(A)
Aspartate transcarbamoylase
35
Which enzyme involved in pyrimidine nucleotide biosynthesis is controlled at the genetic level via repression and derepression?
Answer
(A)
Carbamoyl phosphate synthetase
36
Which molecule inhibits the enzyme aspartate transcarbamoylase, which is involved in pyrimidine biosynthesis?
Answer
(D)
CTP
37
In humans, what is the final product of purine breakdown?
Answer
(A)
Uric acid
38
Which enzyme is missing in humans, leading to the conversion of purines into uric acid?
Answer
(B)
Uricase
39
In non-primate mammals, how is uric acid further processed?
Answer
(A)
Oxidation to allantoin
40
What is the correct order of reactions in the breakdown of adenosine to uric acid?
Answer
(C)
Adenosine→inosine→hypoxanthine→xanthine uric acid
41
Which substance is associated with a metabolic disorder in the breakdown of compounds?
Answer
(B)
Purine
42
Which substance is typically elevated in the blood of individuals with a specific health condition?
Answer
(B)
Uric acid
43
A genetic disorder linked to sex chromosomes, known as Lesch-Nyhan syndrome, results from the absence of which enzyme?
Answer
(A)
Hypoxanthine-guanine phosphoribosyl transferse
44
The absence of HGPRTase, characteristic of a specific genetic condition, can result in which of the following?
Answer
(A)
Compulsive self destructive behaviour with elevated levels of urate in serum
45
In humans, what is the primary end product of the breakdown of a specific type of molecule?
Answer
(A)
β-Alanine
46
A deficiency in specific enzymes is linked to which health condition?
Answer
(A)
Orotate phosphoribosyl transferase and orotidylate decarboxylase
47
The lack of a specific enzyme is associated with which health condition?
Answer
(B)
Orotidylate decarboxylase
48
What enzyme deficiency leads to a specific inherited condition?
Answer
(B)
Xanthine oxidase
49
A deficiency in which enzyme is implicated in a specific metabolic condition?
Answer
(D)
Transaminase
50
Which of the following structures does not contain the cellular components necessary for protein synthesis?
