Carbs 4 - CAC Flashcards
Summarize CAC
CAC is a gateway to aerobic metabolism for any molecule capable of being broken down to one of CAC’s intermediates.
It removes electrons as H atoms and binds them to carriers prducing NADH and FADH2 which transfer them to the electron transfer chain (respiratory chain) which produces ATP.
Why is o2 necessary for aerobic respiration?
O2 acts as an oxyen acceptor at the end of teh respiratory chain.
Without it the whole pathway of CAC & the respiratory chain si energetically unfavourable and so wouldnt occur.
What 3 reactions produce Acetyl CoA from Pyruvate?
Decarboxylation (whihc produces 2 electrons for ATP)
Oxidation
Transfer of the CoA complex
What enzyme catalyzes pyruvate -> Acetyl CoA?
Pyruvate Dehydrogenase
How many sub-units and copies make up pyruvate dehydrogenase?
Pyruvate dehydrogenase is a massive enzyme made up of 3 sub-units (E1,E2,E3) each of which has 10 copies in one enzyme.
Which sub-units catalyze which part of the pyruvate -> Acetyl CoA reaction pathway?
E1 - decarboxylation
E2 - transfers the Acetyl roup to coenzyme A
E3 - recycles lipoyllysine by reducing FAD to FADH2 which becomes 2x NADH.
Why is the clyclic section of CAC known as the “black box”?
Because all the intermediate components remain constant.
How does Carbon enter & leave the CAC?
Every turn of the cycle 2 carbons enter as Acetyl CoA and 2 CO2 molecules leave. It is actually the same CArbons that enter as leave.
Which 3 enzymes can be regulated as points of control in CAC?
Pyruvate dehydrogenase
Alpha-ketoglutare dehydrogenase
Isocitrate dehydrogenase
What ergulates pyruvate dehydrogenase?
ATP and the enzymes immediate products regulate its use so it can be regualted according to the cells needs
wHAT REGULATES ISOCITRATE DEHYDROGENASE?
Allosterically regulated by ATP and NADH (negative) and ADP (positive)
What regulates alpha-ketolutarate dehydrogenase?
Allosterically regulated by ATP, NADH and succinyl CoA (all negative).
Which 2 enzymes in CAC catalyze irreversible (exergonic) reactions?
Isocitrate dehydrogenase and alpha-ketoglutarate dehydrogenase
What use is blocking isocitrate dehydrogenase?
Blockin isocitrate dehydrogenase causes a build up of citrate which ends up in the cytoplasm and causes phosphofuctokinase to block glycolysis.
What use is blocking alpha-ketoglutarate dehydrogenase?
builds up alpha-ketolutarate which is used producing amino acids.
