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Quick Biochemistry - Nucleic Acids (Section 5)

1
Which of the following enzymes is not inhibited by GMP through allosteric regulation?
Answer
(D)
Adenylosuccinate synthetase
2
AMP inhibits which of the following through allosteric regulation?
Answer
(C)
Both (A) and (B)
3
Which enzyme catalyzes the initial distinctive reaction in purine nucleotide synthesis?
Answer
(B)
PRPP glutamyl amido transferase
4
What are the free purine bases that can be repurposed through salvage pathways?
Answer
(D)
Adenine, guanine and hypoxanthine
5
Which enzyme is essential for the recycling of free purine bases?
Answer
(C)
Both (A) and (B)
6
Which of the following molecules can be salvaged by deoxycytidine kinase?
Answer
(D)
Adenine and adenosine
7
Which molecule(s) can be salvaged by adenosine kinase?
Answer
(B)
Adenosine and deoxyadenosine
8
The salvage of purine bases is primarily regulated by which factor?
Answer
(C)
Availability of PRPP
9
When PRPP is available, what process is favored?
Answer
(C)
Salvage of purine bases
10
What is the final product of purine breakdown in the human body?
Answer
(D)
Uric acid
11
Which enzyme is involved in the breakdown of all purines?
Answer
(B)
Purine nucleoside phosphorylase
12
In which organism is uric acid the final product of both purine and protein breakdown?
Answer
(C)
Birds
13
What is the typical daily uric acid excretion range for adult males?
Answer
(D)
40-600 mg
14
Where does the breakdown of purines from food primarily occur?
Answer
(C)
Intestinal mucosa
15
In which cellular compartment does the de novo synthesis of pyrimidine nucleotides take place?
Answer
(B)
Cytosol
16
Which enzyme is used in the creation of new pyrimidine nucleotides and also participates in urea synthesis?
Answer
(B)
Carbamoyl phosphate synthetase
17
What substances supply the nitrogen atoms required to build a pyrimidine nucleus?
Answer
(D)
Glutamine and aspartate
18
From what sources do the carbon atoms in a pyrimidine nucleus originate?
Answer
(B)
CO2 and aspartate
19
Which molecule provides the nitrogen atom at position 1 in the pyrimidine ring?
Answer
(D)
Aspartate
20
Which molecule provides the nitrogen atom at position 3 in the pyrimidine ring?
Answer
(A)
Glutamine
21
Which of the following molecules provides the carbon atom at position 2 of the pyrimidine nucleus?
Answer
(A)
CO₂
22
From the following options, which carbon atoms of the pyrimidine nucleus are contributed by Aspartate?
Answer
(D)
C₄, C₅ and C₆
23
In the de novo synthesis pathway, which pyrimidine nucleotide is generated first?
Answer
(A)
UMP
24
The conversion of uridine diphosphate to deoxyuridine diphosphate necessitates the use of all the following, except
Answer
(C)
Tetrahydrobiopterin
25
The synthesis of which of the following molecules is reduced by Amethopterin and aminopterin?
Answer
(A)
TMP
26
Where does the amino group for the synthesis of CTP and UTP originate?
Answer
(B)
Amide group of glutamine
27
What are the substrates for the CTP synthetase reaction that forms CTP?
Answer
(C)
UTP and glutamine
28
What coenzyme is essential for the synthesis of TMP from dump?
Answer
(C)
N5, N10- Methylene tetrahydrofolate
29
Excluding which of the following, all enzymes involved in the de novo synthesis of pyrimidine nucleotides are found in the cytosol?
Answer
(D)
Dihydro-orotate dehydrogenase
30
In the de novo synthesis of pyrimidine nucleotides, what is the first ring compound formed?
Answer
(B)
Dihydro-orotic acid
31
Tetrahydrofolate plays a crucial role as a coenzyme in the production of which molecule?
Answer
(C)
TMP
32
Which statement regarding thioredoxin reductase is incorrect?
Answer
(A)
It utilizes NADH as a coenzyme
33
Which enzyme is responsible for regulating the initial synthesis of pyrimidine nucleotides?
Answer
(C)
Both (A) and (B)
34
Which molecule inhibits cytosolic carbamoyl phosphate synthetase?
Answer
(A)
UTP
35
Which molecule activates cytosolic carbamoyl phosphate synthetase?
Answer
(B)
PRPP
36
Which molecule inhibits the activity of Aspartate transcarbamoylase?
Answer
(A)
CTP
37
Which of the following compounds cannot be recycled in human metabolic processes?
Answer
(C)
Cytosine
38
From which molecule is B-Aminoisobytyrate produced during breakdown?
Answer
(C)
Thymine
39
During the breakdown of which molecule(s) is free ammonia released?
Answer
(D)
All of these
40
B-Alanine is a product of the catabolism of which combination of molecules?
Answer
(D)
Cytosine and uracil
41
Which coenzyme is essential for the breakdown of pyrimidine bases?
Answer
(B)
NADPH
42
What is the mode of inheritance for primary gout?
Answer
(C)
X-linked recessive
43
Which alteration in PRPP synthetase can lead to primary gout?
Answer
(D)
All of these
44
Which statement about primary gout is not accurate?
Answer
(C)
It can be due to increased activity of hypoxanthine guanine phosphoribosyl transferase
45
Which of the following statements regarding uric acid is false?
Answer
(C)
It is not dissociated at a pH above 5.8
46
In a genetic deficiency of hypoxanthine guanine phosphoribosyl transferase, what happens?
Answer
(B)
Salvage of purines is decreased
47
Which statement about uric acid is incorrect?
Answer
(A)
It can be produced from allantoin
48
Which of the following is NOT a characteristic of primary gout?
Answer
(C)
Urinary excretion of uric acid is reduced
49
Which of the following is NOT a characteristic of allopurinol?
Answer
(A)
It is a structural analogue of uric acid
50
How is orotic aciduria managed?
Answer
(D)
Oral administration of uridine