The citric acid cycle (lecture 25) Flashcards
What are other names for the citric acid cycle?
Krebs cycle
TCA cycle - tricarboxylic acid
What is the purpose of the CAC?
To harvest high-energy electrons from carbon fuels
Unusual to have a circular cycle pathway
Takes out 2 carbons from acetyl CoA & links them to oxaloacetic acid to produce a 6C intermediate – citric acid
Generates NADH, FADH2 & some GTP
What is the order of molecules in the CAC?
Oxaloacetate Citrate Isocitrate Alpha-ketoglutarate Succinyl CoA Succinate Fumerate Malate Oxaloacetate
What kind of molecule is oxaloacetate?
Ketone
4C
What kind of molecule is citrate?
Tricarboxylic acid
Oxaloacetate to citrate
Citrate synthase
Condensation reaction releases CoA from acetyl CoA
Acetyl group and oxaloacetate are joined
Citrate to isocitrate
Aconitase
Isomeration reaction
Hydroxyl group shifted down 1
• Water removed and then added back at a different position
Isocitrate to alpha-ketoglutarate
Isocitrate dehydrogenase
Oxidative decarboxylation
NADH & CO2 released
Alpha-ketoglutarate to succinyl CoA
Alpha-ketoglutarate dehydrogenase complex
Oxidative decarboxylation
Also adds CoA group
NADH & CO2 released
Succinyl CoA to succinate
Succinyl CoA synthetase
Loose CoA
Energy captured by GTP
Succinate to fumerate
Succinate dehydrogenase
Dehydration
FADH2 released
Fumerate to malate
Fumerase
Double bond in fumerate allows water to be added
Malate to oxaloacetate
Malate dehydrogenase
NADH released
What is released overall from the CAC?
3 NADH
1 FADH2
1 GTP
