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76 Cards in this Set
- Front
- Back
adenine numbering
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adenine
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adenosine 5'-diphosphate (ADP)
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adenosine 5'-monophosphate (AMP)
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adenosine 5'-triphosphate (ATP)
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adenosine
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cytosine
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cytidine
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deoxyadenosine 5'-monophosphate (dAMP)
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deoxyadenosine
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guanine
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hypoxanthine
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thymidine
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thymine
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uracil numbering
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uracil
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uridine
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xanthine
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bases and nucleosides can readily cross most cell membranes, but nucleotides and deoxynucleotides are trapped by this
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negative charge of phosphate group(s)
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concentration of ribonucleotides
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millimolar
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concentration of deoxyribonucleotides
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micromolar
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predominant form of nucleotides and deoxynucleotides in cells
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triphosphate (>70%)
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cytosine and thymine are derived form this
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uracil
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in purine synthesis:
base - ? nucleoside - ? nucleotide - ? |
base - hypoxanthine
nucleoside - inosine nucleotide - inosinate/inosine-5'MP (IMP) |
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building purine ring requires ___ ATP
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7
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step 1 of purine synthesis: synthesis of PRPP
___ (produced by ___) --> PRPP catalyzed by ___ |
ribose-5-phosphate (produced by pentose shunt pathway) --> PRPP
catalyzed by PRPP synthase |
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regulates PRPP synthase
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(+) Pi
(-) ADP also... (-) AMP (-) GDP |
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step 2 of purine synthesis: synthesis of PRA
___ atom added catalyzed by ___ |
step 2 of purine synthesis: synthesis of PRA
N9 atom added catalyzed by glutamine PRPP amidotransferase |
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most important regulatory step in purine synthesis
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synthesis of PRA (step 2 adding N9)
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regulates glutamine PRPP amidotransferase
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(+) PRPP
(-) IMP (-) AMP (-) GMP (one site binds IMP and GMP, other binds AMP) |
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step 4 of purine synthesis: ___ deliver C8
catalyzed by ___ |
N10-formal-tetrahydrofolate delivers C8
transformylase activity |
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step 6 of purine synthesis: closure of ___ ring
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imidazole ring
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only part of aspartate that is retained in purine synthesis
(rest cleaved off as ___) |
N1
(fumarate) |
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fumarate can be used in this
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tricarboxylic cycle
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step 10 of purine synthesis: ___ delivers C2
catalyzed by ___ |
N10-formyl-tetrahydrofolate delivers C2
transformylase activity |
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1st step in branched pathway for synthesis of AMP or GMP:
- ___ to form XMP (to become GMP) catalyzed by ___ regulated by ___ OR - ___ to form adenylosuccinate (to become AMP) catalyzed by ___ regulated by ___ |
- oxidation of C2 to form XMP (to become GMP)
catalyzed by IMP dehydrogenase regulated by GMP (-) OR - substitution of Asp for C=O to form adenylosuccinate (to become AMP) catalyzed by adenylosuccinate synthetase regulated by AMP (-), GTP (+) |
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2nd step in branched pathway for synthesis of AMP or GMP:
-substitution of ___ to form GMP (brought in by ___) catalyzed by ___ regulated by ___ OR -removal of ___ to form AMP catalyzed by ___ |
-substitution of C-NH2 for C=O to form GMP (brought in by glutamine)
catalyzed by GMP synthetase regulated by ATP (+) OR -removal of fumarate to form AMP catalyzed by adenylosuccinase |
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performed with purines to increase TCA intermediate under stress
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AMP --> IMP --> AMP + fumarate
(just for the purpose of removing fumarate) |
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deficiency of ___ leads to muscle cramps during exercise
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AMP deaminase (can't make IMP to convert back to AMP to release fumarate)
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in purine nucleotide degeneration, nucleotides lose ___ then lose ___
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PO4 then ribose
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purine nucleotide degeneration is catalyzed by ___
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xanthine dehydrogenase/xanthine oxidase
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final produce of purine nucleotide degeneration
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uric acid
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may cause gout if it precipitates in joints
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uric acid (final produce of purine degeneration)
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inhibits xanthine oxidase to prevent gout
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allopurinol
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order of pieces added
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order of pieces added
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cause of gout:
___ --> increased glucose-6-PO4 --> pentose shunt flux --> increased R-5-P --> ___ |
beta glucose-6-phosphatase
PRPP |
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cause of gout:
elevated level of this enzyme |
PRPP synthetase
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cause of gout:
loss of feedback inhibition of ___ by ___ |
glutamine PRPP amidotransferase by AMP, GMP and IMP
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cause of gout:
decreased ___ --> increased PRPP --> increased ___ |
decreased HGPRT
increased purine biosynthesis |
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sex-linked gene on x chromsome leading to men getting more gout than women if mutated
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HGPRT
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partial decreased in HGPRT --> ___
severe decreased or lack of HGPRT --> ___ |
gout
lesch-nyhan syndrome |
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added last in pyrimidine synthesis
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ribose
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pyrimidine synthesis:
base - ? nucleoside - ? nucleotide - ? |
base - uracil
nucleoside - uridine nucleotide - uridylate (UMP) |
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cofactor used only for dTMP synthesis
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folate cofactor
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3 parts of trifunctional enzyme in pyrimidine synthesis
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(CAD)
CPS II ACTase Dihydroorotase |
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principal regulatory site in pyrimidine synthesis
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CPS II
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step 1 of pyrimidine synthesis: carbamoyl phosphate
(synthesized from ___ and ___) catalyzed by ___ |
glutamine and CO2
catalyzed by CPS II |
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regulates CPS II
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(+) ATP
(+) PRPP (-) UTP |
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step 2 of pyrimidine synthesis: addition of aspartate
catalyzed by ___ |
ACTase
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regulates ACTase
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(+) ATP
(-) CTP ONLY IN BACTERIA! |
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regulated only in bacteria
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ACTase
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step 3 of pyrimidine synthesis: ring closure
catalyzed by ___ |
dihydroorotase
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step 4 of pyrimidine synthesis: ring oxidation (C=C)
catalyzed by ___ uses ___ as proximal cofactor and ___ as ultimate electron acceptor reaction takes place in ___ |
catalyzed by dihydroorotate dehydrogenase
uses NAD+ as proximal cofactor and coenzyme Q as ultimate electron acceptor reaction takes place in mitochondria |
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reaction that occurs in mitochondria
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pyrimidine ring oxidation
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step 5 of pyrimidine synthesis: addition of ribose
forms ___ catalyzed by ___ uses ___ as an activated substrate reactions takes place in ___ |
forms OMP
catalyzed by ORPTase uses PRPP as an activated substrate reactions takes place in cytosol |
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deficiency of either of these 2 enzymes causes orotic aciduria
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ORPTase
OMP decarboxylase |
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step 6 of pyrimidine synthesis: removal of COO- at C6
forms ___ catalyzed by ___ regulated by |
forms UMP
catalyzed OMP decarboxylase regulated by UMP (-) |
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synthesis of CTP from UMP:
-first UMP --> ___ -use ___ and ___ to replace carbonyl with ___ -catalyzed by ___ -regulated by ___ |
-first UMP --> UDP --> UTP
-use ATP and glutamine to replace carbonyl with amino acid -catalyzed by CTP synthetase -regulated by CTP (-) |
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synthesis of dTMP from UMP:
-requires folate cofactor - ___ which adds ___ to ___ - H4-folate is ___ to H2-folate in the process (must use ___ to go back, H2-->H4) |
-requires folate cofactor - N5N10-methylene H4-folate which adds -CH3 to C5
- H4-folate is reduced to H2-folate (must use dihydrofolate reductase to go back, H2-->H4) |
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first 3 steps of pyrimidine degradation and enzymes involved
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dephosphorylation
deamination (cytidine deaminase... cytidine --> uridine) deribosylation (phosphorylase... uridine --> uracil) |
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key irreversible step of pyrimidine degradation and its catalyst
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reduction of ring (double bond to single bond)
catalyzed by dihydrouracil dehydrogenase |
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ribonucleotide reductase reaction:
-used for creating ___ -ribose ___ is reduced to ___ -reducing source is ___ -intermediate carrier is ___ or ___ -substrate must be at ___ level |
-used for creating deoxynucleotides
-ribose 2'-OH is reduced to 2'-H -reducing source is NADPH -intermediate carrier is thioredoxin or glutaredoxin -substrate must be at diphosphate level (NDP--> dNDP) |
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regulates ribonucleotide reductase
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(-) high dTTP
(-) high dATP |