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16 Cards in this Set
- Front
- Back
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Pyruvate
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i. Formed in cytosol
ii. Transported into the mitochondrion by a proton symporter |
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Inside the mitochondrion, pyruvate is....
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i. Oxidateively decarboxylated to acetyl-CoA by pyruvate dehydrogenase multienzyme complex
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PDH reaction steps
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a. Pyruvate is covalently bound to TPP associated with the first enzyme of the complex pyruvate dehydrogenase
b. Dihydroliplyl transacetylase catalyzes the transfer of acetyl group to CoA-SH which leaves the lipoic acid in the reduced, sulfhydryl form c. Oxidized form of lipoamide is regenerated by dihydrolipoyl dehydrogenase |
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AcetylCoA+oxaloacetate→ citrate+CoASH
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a. Irreversible
b. Other roles of citrate→ source of other synthetic pathways, regulation of other reactions, source of reducing equivalents c. Catalyzed by citrate synthetase |
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Citrate→ isocitrate
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a. Catalyzed by acontinase
b. Stereospecific c. CO2 lost |
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Isocitrate→ α-ketoglutarate
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a. Oxidative decarboxylation
b. Catalyzed by isocitrate dehydrogenase c. Produces first NADH and first CO2 d. Rate-limiting step of TCA cycle |
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α-ketoglutarate→ succinyl-CoA
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a. Catalyzed by α-ketoglutarate dehydrogenase
b. NADH synthesized c. CO2 lost |
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α-ketoglutarate dehydrogenase
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a. Catalyzes reversible reaction
b. Similar to PDHC→ *3 catalytic subunits (E1, E2, E3) c. *Requires TPP, lipoic acid, CoASH, RAD, NAD+ d. *Not regulated by phosphorylation |
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Succinyl-CoA→ succinate
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a. Only substrate level phosphorylation of TCA cycle
b. GTP synthesized catalyzed by succinylCoA synthetase |
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Succinate→ fumarate
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a. FADH2 made
b. Reversible c. Catalyzed by succinate dehydrogenase |
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Fumarate→ malate
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a. Hydrolysis reaction
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Malate→ oxaloacetate
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a. Catalyzed by malate dehydrogenase
b. Produces NADH |
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Control of TCA cycle
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a. Rate of ATP utilization generally determines the rate of TCA cycle activity
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Other control mechanisms
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i. Citrate synthase inhibited by succinylCoA
ii. Isocitrate DH stimulated by APD, inhibited by ATP iii. α-ketoglutarate inhibited by succinylCoA, NADH, and ATP |
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Malate-aspartate shuttle
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a. NADH does not enter directly into mitochondrion
b. Must be shuttled across membrane into matrix |
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1 molecule of glucose produces.....
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38 ATPs by glycolysis and TCA
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