Lecture 27 Flashcards
Where does the citric acid cycle occur?
In the mitochondria
What enters the citric acid cycle?
2x carbon molecules as acetyl-CoA
Where does the acetyl-CoA used in the CAC come from?
Produced in glycolysis and the beta-oxidation reaction
What exits the citric acid cycle?
2x CO2, 3NADH, 3H+, ATP and FADH2
What are the two parts of the CAC?
The release of the C molecules and the regeneration of the starting molecule
What is the first stage of the CAC?
Condensation of acetyl-CoA with oxaloacetate
Where does the energy come from in the condensation of acetyl-CoA with oxaloacetate?
The hydrolysis of CoA from acetyl-CoA
Is the condensation of acetyl-CoA with oxaloacetate energetically favourable to unfavourable?
Energetically favourable
What does the condensation of acetyl-CoA with oxaloacetate produce?
Citrate
What happens to citrate after the condensation reaciton?
Undergoes isomerisation
How does 1080 poisoning occur?
Fluroacetate forms fluorocitrate which is converted to a substrate that binds tightly to the aconitase enzyme, inactivating it
What type of reaction is the removal of the carbons?
Oxidative decarboxylation reactions
How does removal of the first carbon occur?
In two steps; oxidation of the molecule removing 2x H then decarboxylation, removing the CO2
How does removal of the second carbon occur?
In one step; oxidation and decarboxylation at the same time
What does the removal of the CoA from succinyl to succinate release?
GTP
What is GTP?
An energy equivalent of ATP
How is ATP generated from GTP?
GTP undergoes a reaction with ADP to form an equilibrium, producing ATP and GDP
What is a substrate level phosphorylation?
The direct use of energy from a substrate molecule to drive the synthesis of ATP
How does succinate rearrange to form oxaloacetate?
Succinate is oxidised, hydrated and then oxidised again
What is reduced in the first oxidation reaction of succinate?
FAD to FADH2
What is reduced in the second oxidation reaction of succinate?
NAD+ to NADH + H+
What is the overall reaction for the CAC?
Acetyl-CoA + 3NAD+ + FAD + 2H2O + GDP + Pi ——-> 2CO2 + CoASH + 3NADH + 3H+ + FADH2 + GTP
Is the CAC energetically favourable or unfavourable?
Favourable -44.3kJ/mol
What is the shared enzyme in the CAC?
SDH
