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biochem 2 > Nucleotide metabolism > Flashcards

Nucleotide metabolism Flashcards

1
Q

nucleoside

A

linking a nitrogenous base to the 1’ position of the ribose ring

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2
Q

nucletodie

A

nucleoside added to phosphate at 5’ position of ribose ring

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3
Q

deoxyribonucleotide

A

hydroxyl group at 2’ position of ribose ring is replaced with H

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4
Q

de novo synthesis

A

makeing nucleotide from scratch

takes a lot of energy

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5
Q

salavage pathways

A

generation of nucleotides from free bases and nucleosides from diet

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6
Q

first step in purine synthesis

A

PRPP generation

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7
Q

committed step of purine synthesis

A

amidophosphoribosyltransferase forming PRA from PRPP

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8
Q

what is the first purine syntheiszed

A

IMP

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9
Q

what is IMP a precusor for

A

synthesis of both AMP and GMP

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10
Q

how are carbon and/or nitrogen atoms donating to de novo pathway

A

amino acids

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11
Q

what provides carbon and oxygen to de novo pathway

A

CO2

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12
Q

what serves as a donor of one-carbon groups to de novo pathway

A

N10-formyl THF

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13
Q

what is the rate limiting enzyme of GMP synthase

A

IMP dehydrogenase

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14
Q

what inhibits IMP dehydrogenase

A

GMP

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15
Q

what is the rate limiting enzyme of AMP synthesis

A

adenylosuccinate synthase

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16
Q

what inhibits adenylosuccinate synthase

A

AMP

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17
Q

how do AMP and GMP get converted into ATP and GTP

A

nucleoside 5’ monophosphate kinases and nucleoside 5’diphosphate kinases

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18
Q

what inhibits PRPPP synthetase

A

ADP and GDP

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19
Q

what is PRPP required for

A

synthesis of both purines and pyrimidines

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20
Q

what inhibits amidophosphoribosyltransferase

A

AMP and GMP

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21
Q

when is de novo purine synthesis limited

A

when purine nucleotides are abudent

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22
Q

incrase in PRPP do waht

A

stimulate de novo synthesis

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23
Q

what is the end product of purine metabolism

A

uric acid

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24
Q

how is uric acid excreted

A

kidney

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25
Q

hyperuricemia

A

excess uric acid in blood

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26
Q

what cause can reduced excretion of uric acid

A

renal insufficieny

metabolic acidosis

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27
Q

what can cause incrased production of uric acid

A

increased nucleotide turnover

diet rich in purine

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28
Q

how does EtOH affect uric acid

A

causes decreases excertion and increased production

29
Q

is uric acid soluble or insoluble

A

insoluble

30
Q

what is a possible consquence of increased uric acid

A

crystals of sodium urate deposite in joints, cause gouty arthritis

31
Q

how do you treat hyperuricemia

A

allopurinol

32
Q

how does allopurinol work

A

gets metabolized to oxypurinol which is a compoetitive inhibitor of xanthine oxidase

33
Q

where does the synthesis of UMP take place

A

5 steps in cytoplasm, one in mitochondria

34
Q

what is the first step in UMP synthesis

A

carbamoyl phosphate synthetase II

35
Q

how do you get OMP to UMP

A

OMP decarbozylase

36
Q

what are the first 3 steps of ump synthesis catalyzed by

A

CAD

37
Q

what are teh last 2 steps of UMP synthase catalyzed by

A

UMP synthase

38
Q

what causes orotic aciduria

A

defect in UMP synthase

39
Q

symptoms of orotic aciduria

A

symptoms similiar to megaloblastic anemia

40
Q

how do you treat orotic aciduria

A

pyrimidine supplementation

41
Q

how do you get UTP to CTP

A

CTP synthase,

42
Q

what does CTP use as a amino group donor

A

glutamine

43
Q

how does UTP affect CTP synthase

A

as UTP levels increase, enzyme becomes more efficient at binding UTP

44
Q

how does CTP affect CTP synthase

A

negative feedback

45
Q

what catalyzes synthesis of deoxyribonucleutides

A

ribonucleotide reductase

46
Q

what gets oxidized during ribonucleotide reductase

A

thioredoxin

47
Q

wha tinhibits ribonucletodie reductase

A

hydroxyurea

48
Q

what causes SCID

A

mutation in adenosine deaminase

49
Q

do cells contain ribonucletodies of thymine

A

no

50
Q

what catalyzes synthesis of dTMP

A

thymidylate syntahse

51
Q

what happens when you inibt thymidylate synthase

A

prevent cell proliferation

52
Q

inhibitor of thymidylate synthase

A

5-flurorourical

53
Q

what happens when you degrate pyrimidine nucletodies

A

beta-amino acids

54
Q

what is unique to thymine degration

A

beta-aminoisobutryate proudction

55
Q

where does most de novo synthesis of nucleotides take palce

A

liver

56
Q

what 2 enzymes do salavage of bases require

A

HGPRTase and APRTase

57
Q

how do you get IMP in salaver pathway

A

hypoxanthine + PRPP

58
Q

how do you get GMP in salvage pathway

A

Guanine + PRPP

59
Q

how do you get AMP in salvage pathway

A

Adenine + PRPP

60
Q

how does generation of IMP, GMP, and AMP by salvage pathways affect de novo synthesis

A

decreases it

61
Q

what is lesch-nyhan syndrome caused by

A

deficeny of HGPRTase activity

62
Q

symptoms of lesch-nyhan syndrome

A

hyperuricemia, uric acid stones, intellectual disablity, biting of fingers/lipis

63
Q

what catalyzes pyrimidine bases and nucleosides

A

pyrimidine phosphoribosyltranserase

64
Q

is cytosin salvaged in humans

A

no

65
Q

what inhbiits CTP synthase

A

CTP

66
Q

what inhbiits ribonucleotide reductase

A

NTPs and dNTPs

67
Q

what inhbiits hypoxanthine guanine phosphoribosyltransferase

A

IMP and GMP

68
Q

what inhibits adenine phosphoribosyltransferase

A

AMP

biochem 2 (22 decks)

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