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BMSC 230 #2 > module 13- nucleotide metabolism > Flashcards

module 13- nucleotide metabolism Flashcards

(76 cards)

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1
Q

dietary nucleic acids are degraded & absorbed as

A

nucleosides

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2
Q

what 2 pathways can purine nucleotides be synthesized?

A

de novo or salvage

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3
Q

lesch-nyhan syndrome

A

genetic defect in purine salvage pathway = lot of de novo pathway, stops HGPRT coding, affects males, neuro symptoms

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4
Q

what causes gout

A

elevation of uric acid= crystals

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5
Q

pyrimidine ring is assembled & attached to

A

ribose sugar

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6
Q

some anti-cancer & anti-viral therapeutics inhibit

A

nucleotide metabolism

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7
Q

how are thymidine deoxynucleotides synthesized

A

methylation reaction

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8
Q

ribonucleotide reductase uses ( ) as reducing agent to convert ribonucleotides to deoxyribonucleotides

A

NADPH

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9
Q

nucleases- what do they do & what do they produce

A

hydrolyze phosphodiester bonds, produce monophosphate nucleotides

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10
Q

phosphatases

A

removes phosphate groups

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11
Q

nucleosidases

A

hydrolyze link between sugar & nitrogenous base

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12
Q

nucleotides vs nucleosides

A

tides have phosphate group

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13
Q

where do most of the nucleosides get absorbed

A

enterocyte

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14
Q

T or F: most nucleosides are further degraded after being absorbed

A

T

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15
Q

where do most of nucleotides that we need for nucleic acid synthesis come from

A

biosynthetic pathways not dietary sources

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16
Q

what do nucleotides consist of

A

nitrogenous base, ribose sugar & phosphate groups

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17
Q

ribose vs deoxyribose

A

ribose has -OH group and deoxyribose has -H group

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18
Q

is ATP a nucleotide

A

yes

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19
Q

ATP bonds

A

anhydride

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20
Q

adenine-based nucleotides are components of what 3 coenyzmes?

A

NAD, FAD & CoA

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21
Q

how do nucleotides form activated substrates

A

linking to other biomolecules

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22
Q

T or F: some nucleotides & nucleosides are cellular & physiological regulators

A

T

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23
Q

adenosine affect on heart

A

decreases heart rate & decreases force of contraction

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24
Q

de novo pathway

A

start with ribose 5-P & build purine ring on it to form nucleotides

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25
T or F: amino acids are important contributors of the atoms in the purine ring
T
26
what are 5 contributors to the purine ring
aspartate, formate, glutamine, glycine & CO2
27
how to make ribose 5-P reactive (2)
1) ATP is used to form PRPP 2) IMP is precursor for AMP & GMP
28
what is the regulatory enzyme of nucleotide synthesis
glutamine-PRPP amidotransferase
29
T or F: ATP is not required to make a nucleotide, uses GTP instead
T
30
IMP can be used to make ( ) or ( )
AMP or GMP
31
how to form AMP
aspartate donates amino group
32
how to form GMP
glutamine donates amino group
33
how is the de novo pathway inhibited
allosteric inhibition of glutamine-PRPP amidotrasferase by IMP, AMP & GMP (end products of pathway)
34
what 2 inhibition pathways are used in the de novo pathway
concerted & sequential
35
what does IMP do during sequential inhibition
inhibits glutamine-PRPP amidotransferase
36
salvage pathway
joins free purine bases together
37
what are the 3 purines that are salvaged
adenine, guanine & hypoxanthine
38
hypoxanthine results from what
deamination of adenine
39
what does the APRT enzyme form
AMP
40
what is the major vs minor enzymes in the salvage pathway
minor- APRT major- HGPRT (hypoxanthine-guanine)
41
treatment of gout
limiting purine consumption- meat & beer
42
allopurinol
inhibits uric acid production
43
uracil, cytosine & thymine are made
de novo
44
what 3 components are required for pyrimidine backbone
glutamine, aspartate & CO2
45
what is the regulatory enzyme of pyrimidine synthesis
carbamoyl phosphate synthease II
46
what are the 4 precursors for pyrimidines
ribose 5-P, CO2, glutamine & aspartate
47
what is enzyme CPS II inhibited by
UTP
48
CPS I vs CPS II - process, location, N donor & regulatory effectors
CPS I- urea synthesis, mitochondrial matrix, NH4, stimulates N-acetylGlu & arginine CPS II- pyrimidine synthesis, cytosol, glutamine, inhibits UTP & stimulates ATP & PRPP
49
the 1st committed stop in pyrimidine synthesis is catalyzed by
ATCase
50
ATCase is allosterically inhibited by
CTP
51
what is the start vs end of pyrimidine synthesis
starts with ASP + CP, CTP is end product
52
pyrimidine synthesis steps
ASP + CP -> orotate -> OMP -> UMP -> UDP -> UTP -> CTP
53
substrates for DNA & RNA synthesis
nucleotide triphosphates
54
nucleoside monophosphate kinases are specific for the ( ) but not the ( )
base, ribose sugar
55
where does ATP come from
oxidative phosphorylation in the mitochondria or glycolysis
56
deoxyribonucleotides are synthesized from nucleoside diphosphate molecules by a reduction reaction carried out by what enzyme?
ribonucleic reductase
57
4 substrates for ribonucleic reductase
ADP, GDP, CDP & UDP
58
the source of reducing equivalents for the synthesis of deoxyribonucleotides comes from
NADPH from pentose phosphate pathway
59
ribonucleoside reductase complex
multi-subunit enzyme that is allosterically regulated
60
how is the proper balance of deoxyribonucleotides obtained from the ribonucleoside reductase complex
regulation site & substrate specificity site
61
ATP activates enzyme activity in the regulation site (R1) and ( ) inhibits it
dATP
62
what subunit is the regulation site on
R1
63
where can dCTP be used
DNA synthesis or deamination to produce dUTP
64
dUTP can be converted to what
dUMP
65
what is the only substrate for thymidylate synthase
dUMP
66
T or F: uracil & thymine structure only differ by a methyl group
T
67
what reaction does thymidylate synthase catalyze?
methylation
68
dihydrofolate reductase
methyelne-tetrahydrofolate reduces to tetrahydrfolate using NADPH
69
what is dTMP converted to
dTTP- substrate for DNA synthesis
70
acyclovir
treats herpes simplex- haults DNA synthesis bc no ribose ring on it to continue synthesis
71
anti-viral therapies
reverse transcriptase, stops DNA synthesis
72
what is the target for anti-cancer drugs
thymidylate synthase
73
5-fluorouracil
similar structure to UMP, inactivates thymidylate synthase to stop DNA production
74
3 compounds that are analogues of dihydrofolate & inhibit it for anti-cancer drugs
methotrexate, aminopterin & trimethoprim
75
which molecule does not regulate de novo synthesis of purines
UMP
76
what is the major end product of purine degradation
uric acid

BMSC 230 #2 (15 decks)

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