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biochemistry > nucleotide structure, function and metabolism > Flashcards

nucleotide structure, function and metabolism Flashcards

1
Q

define chromatin

A

protein + nuclear DNA

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2
Q

what do nucleotides contain

A

base, sugar phosphate

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3
Q

define nucleoside

A

when a base is attached to the sugar

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4
Q

what are the purines

A

adenine and guanine

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5
Q

what are the pyrimidines

A

cytosine, uracil, thymine

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6
Q

what catalyzes the reaction of nucleotide phosphate to 2’-deoxynucleotide diphosphate

A

ribonucleotide reductase (ATP stimulates and dATP inhibits)

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7
Q

what do ribonucleases do

A

covert RNA to short oligomers

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8
Q

what do deoxyribonucleases do

A

convert DNA to short oligomers

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9
Q

what do phosphodiesterases do

A

convert oligomers to nucleotide monophosphates or deoxynucleoside monophosphates

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10
Q

what do nucleotidases do

A

convert the NMPs and dNMPs into nucleosides and deoxynucleosides

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11
Q

what do nucleosidases do

A

remove ribose group and convert them into pyrimidines and purines

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12
Q

what catalyzes the conversion of inosine to hypoxanthine

A

PNP

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13
Q

what catalyzes the conversion of hypoxanthine to xanthine

A

xanthine oxidase

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14
Q

what does adenosine deaminase (ADA) do

A

plays important role in adenosine homeostasis and modulates signaling by extracellular adenosine and so contributes indirectly to signaling

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15
Q

what is the structure of xanthine

A

has 2 flavin adenine dinucleotides (FADs), 2 Mo atoms, and 8 Fe atoms per molecule of enzyme

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16
Q

what is gout characterized by

A

intensely painful and inflamed joints and high levels of uric acid levels in blood

17
Q

what catalyzes the conversion of dTDP and dTTP to deoxythymidine

A

nucleotidase

18
Q

what catalyzes the conversion of deoxythymidine to thymine

A

uridine phosphorylase

19
Q

what is the source of ring atoms for purine bases

A

CO2, Gln, Gly, Asp, N10-formyl THF

20
Q

what is the source of ring atoms for pyrimidine bases

A

HCO3-, Gln, Asp, N5, N10-methylene THF

21
Q

what is the committed step in the purine synthesis

A

phosphoribosyl amine

22
Q

what molecule is formed from the committed step of the purine biosynthesis

A

hypoxanthine ribose phosphate/inosine monophosphate

23
Q

what are the 2 salvage enzymes in the purine biosynthesis

A

hypoxanthine guanine phosphoribosyl transferase

adenine phosphorirobosyl transferase

24
Q

what catalyzes the conversion of alpha-d-ribose-5-phosphate to PRPP

A

PRPP synthetase

25
Q

what is PRPP synthesized from

A

ribose phosphate and ATP

26
Q

what is the ribose for purines initially contributed by

A

phosphoribosylpyrophosphate

27
Q

where does methotrexate convert

A

in the liver

28
Q

what is methotrexate

A

inhibitor of DNA synthesis

binds dihydrofolate reductase 100 fold more tightly

29
Q

what is AMP synthesis stimulated by

A

GTP

30
Q

what is GMP synthesis stimulated by

A

ATP

31
Q

what is the pyrimidine ring synthesized from

A

carbamoyl phosphate and aspartate by aspartate-transcarbamoylase

32
Q

what is the committed step of the pyrimidine synthesis

A

formation of n-carbamoyl aspartate from aspartate and carbamoyl phosphate

33
Q

where is orotate synthesized

A

mitochondria

34
Q

what is the immediate hydrogen donor for the reduction of ribonucleoside diphosphate

A

reduced thioredoxin or glutaredoxin

35
Q

what is aspartate trascarbamoylase feedback inhibited by in the pyridine synthesis

A

CTP

36
Q

what is the limiting factor for DNA synthesis

A

dTTP

biochemistry (6 decks)

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