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14 Cards in this Set
- Front
- Back
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TCA cycle
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-occurs under aerobic condtions
-pyruvate from glycolysis is taken to mito & oxidized which forms co2,H2O,NADH & 15 ATP/pyruvate -when E charge is dec in cell,pyruvate is oxidized -once in mito pyruvate encounters 2 enzymes:pyruvate carboxylase & PDH -byproducts are 2CO2,1GTP,3NADH,1 FADH |
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Pyruvate carboxylase
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-pyruvate enters cell & CoA is acetylated
-this activates pyruvate carboxylase -which directs pyruvate to gluconeogenesis -defeciencies lead to lactic acid build up & CNS damage |
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PDH
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-dec E in cell inhibits pyruv carbox
-pyruvate is metabolized via PDH |
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PDH complex
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made of 3 enzymes:
-thiamine PP (pyrophosphate) -lipoate (dihydrolipoyl transacetylase) -riboflavin aka FAD(dihydrolipoyl dehydrogenase) deficiencies: -thiamine leads to wernicke-korsakoff inc pyruvate levels,alanine,& lactate -lipoate is inhibited w/ binding of arsinate |
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Regulation of PDH
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-negative regulators:NADH,Acetyl CoA
-positive regulators: pyruvate,NAD,AMP,CoA |
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Rxn 1 TCA cycle: Citrate synthase
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-conensation of methyl C of acetyl CoA w/ keto C of OAA
-has lots of free E -very imp. in keeping cycle going in forward direction -Regulation: inhibited by ATP & citrate |
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Rxn 2:Aconitase
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citrate--[aconitase]=>isocitrate
-isomerization of citrate to isocitrate,OH from central C of citrate -stereospecific nature determines if the CO2 lost as isocitrate is oxidized t succinyl CoA -regulation:inhibited by fluoroacetate |
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Rxn 3: Isocitrate dehydrogenase
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isocitrate--[Isocitrate dehydrogenase]=>alpha ketogluterate & NADH & CO2
-1st RATE LIMITING STEP & 1st YIELD OF NADH IN TCA -regulation: activated by NAD+ & ADP inhibited by NADH |
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Rxn 4:alpha ketogluterate dehydrogenase
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isocitrate--[alpha ketogluterate dehydrogenase]=>succinyl CoA & CO2& NADH
-succ CoA & alpha keto are imp. in a.a synth -high free E change -regulation: inhibited by NADH/ATP/succ CoA |
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Rxn 5: Succinyl CoA synthetase
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succ CoA--[CoA synthetase]=>succinate,GTP,&CoA-SH
-reversible -used in heme production |
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Rxn 6:Succinate dehydrogenase
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succinate--[Succinate dehydrogenase]=>fumarate & FADH2
-reversible -membrane bound enzyme -FADH2 goes on to be oxidized by COq 10 in ox phos |
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Rxn 7:Fumarase
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fumarate + H2O --[fumarase]=>malate -reversble
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Rxn 8:Malate dehydrogenase
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malate(can be xported through cytoplasm to initiate gluconeogenesis)
+ NAD --[malate dehydrogenase]=> oxaloacetate & NADH & H+ -reverisble -synth Asp & pyrimidines |
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Regulation of TCA
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Availability of Acetyl CoA regulated by PDH:
Inhibition- NADH,NAD+ &Acetyl CoA Stimulation- CoA & AMP -ATP & citrate inhibit citrate synthase Isocitrate DH: -Inhib:NADH,NAD+ -Stim:ADP Ketogluterate DH: -Inhib:NADH,ATP,succinyl-CoA |
