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