Which of these is a purine nucleoside?
Guanosine
Cytosine
Uridine
Thymidine
Guanosine
What is the difference between de novo and salvage pathway of nucleotides?
The former relates to synthesis of nucleotide from its precursor molecule and later involves in synthesis of nucleotide from nucleobases.
What enzyme acts in opposite to nucleoside phosphorylase?
Nucleoside kinase
What molecule acts as an activated sugar-phosphate donor to utilize a nucleobase in the synthesis of nucleotide?
Phosphoribosyl pyrophosphate
PRPP synthetase activates ________ of ribose-5-phosphate by transferring to it the pyrophosphate moiety of ATP.
C1
What enzyme catalyzes the transfer of a free nitrogen base to phosphoribosyl pyrophosphate (PRPP)?
Phosphoribosyltransferase
What carbon of ribose-5-phosphate accepts the amide nitrogen of glutamine?
C1
5-Phosphoribosyl-? -D-1-pyrophosphate (PRPP) is an activated sugar-phosphate donor that is observed in which pathway of nucleotide synthesis?
Salvage and de novo pathways
Phosphodiesterases catalyze which reaction?
Breakdown of oligonucleotides to nucleoside monophosphates
Identify each reaction catalyzed by a nucleotidase, a phosphorylase, or a phosphoribosyltransferase.
Since GMPis a nucleotide and guanosine is a nucleoside, the conversion of GMP to guanosine is catalyzed by nucleotidase.
Since guanosine is a nucleoside and guanine is a free base, the conversion of guanosine to guanine and vice versa is catalyzed by phos
Using either names or formulas, complete pathways for the conversion of uracil to dTTP and to dCTP.
Match the cofactors to the reactions they are involved in and their effect on this reactions.
What is the purine base on inosine monophosphate?
Hypoxanthine
What makes the amide nitrogen of glutamine active to be used as a substrate for glutamine amidotransferase?
ATP breakdown
What nitrogen atoms of the purine ring is contributed by glutamine?
N3 and N9
What does glycine and phosphoribosylamine contribute to the purine ring?
N7, C4 and C5
The carbons C2 and C8 is incorporated by ________ to the growing purine ring.
Formyl tetrahydrofolate
What nitrogen of the purine ring is added by an amino group of aspartate?
N1
What carbon is attached to growing purine ring by CO2 dependent carboxylation?
C6
What is the energy source for conversion of IMP to AMP?
GTP
What enzyme is required by ATP to convert GDP, UDP and CDP to its respective triphosphate state?
Nucleoside diphosphate kinase
Match the C and N atom in purine ring with its correct source (precursor):
1) N-1
2) C-2
3) N-3
4) C-4
5) C-5
6) C-6
7) N-7
8) C-8
9) N-9
A) glycerine
B) 10-formyl-THF
C) glutamine
D) aspartate
E) CO2
1:D
2:B
3:C
4:A
5:A
6:E
7:A
8:B
9:C
Which of the following does NOT result in nucleic acid degradation?
-Cell death
-Unstable mRNA species
-Replication during cell division
-UV damage to DNA
Replication during cell division
Which of these enzymes cleaves the glycosidic bond between nitrogen base and sugar of a nucleoside?
Phosphodiesterase
Nucleotidases
Pyrophosphate synthetase
Nucleoside phosphorylase
Nucleoside phosphorylase
Which of theses molecules are the oxidized form of purine?
Uric acid
Ceramide
Amide
Urea
Uric acid
Which of these molecules acts as a precursor to formation of pyrimidine ring?
Glutamate
Glutamine
Asparagine
Aspartate
Aspartate
The pyrimidine synthesis begins with the synthesis of ________ phosphate.
Carbamoyl
Aspartate is attached by its alpha amino group and activated carboxylic group on carbamoyl phosphate to yield carbamoyl aspartate by the enzyme ________.
Aspartate transcarbamoylase
In a cell where does the conversion of dihydroorotate to orotate takes place?
Mitochondria
In a series of reactions, various precursors are converted via de novo synthesis to pyrimidines. Match the C or N atom in uridine with its correct source:
1) N-1
2) C-2
3) N-3
4) C-4
5) C-5
6) C-6
A) carbamoyl phosphate
B) aspartate
C) glutamine
D) CO2
1:A
2:A
3:B
4:B
5:B
6:B
Arrange the first 5 steps of the de novo biosynthesis of cytosine triphosphate in their correct order:
1. cyclization to dihydroorotate
2. transfer of a carbamoyl group
3. conversion of bicarbonate to carbamoyl phosphate
4. nucleotide synthesis catalyzed
3. conversion of bicarbonate to carbamoyl phosphate
2. transfer of a carbamoyl group
1. cyclization to dihydroorotate
5. dehydrogenation to yield a conjugated enone system
4. nucleotide synthesis catalyzed by
What is a typical intracellular ATP concentration?
2 to 5 mM
The ultimate source of electrons for reduction of ribonucleotide is ________.
NADPH
Which of these nucleotides bind in activity site of ribonucleotide reductase?
dATP
What molecule serves as a immediate precursor for the synthesis of dTTP?
dUMP
What is the source of electrons for the reduction of ribonucleotides?
NADPH via thioredoxin or glutaredoxin