Citric Acid Cycle Flashcards
Which 3 steps in the CAC are regulated?
Steps 1, 3, 4
Why are steps 1, 3, and 4 of the CAC regulated?
They are the irreversible steps
What determines the rate of the CAC?
The NAD+/NADH ratio
How does the rate of the CAC change when there is a lot of NAD+?
It speeds up because lots of NAD+ indicates low NADH and the cell needs more energy
How does the rate of the CAC change when there is a lot of NADH?
It slows down because NADH buildup indicates the cell has enough energy
Which two molecules inhibit the CAC as a whole?
NADH and ATP
Why is succinyl-CoA a feedback inhibitor?
It is downstream of all the regulated steps
Why is the CAC called “the traffic circle of life”?
Lots of intermediates are taken out and used in other pathways as precursors
How does the cell replenish CAC intermediates when it starts to run out?
The buildup of acetyl-CoA activates pyruvate carboxylase and converts some pyruvate into oxaloacetate to replenish the CAC
What is the energy source for the step 1 of the CAC?
Hydrolysis of acetyl-CoA, a thioester
Why is it necessary to convert citrate to isocitrate?
The hydroxyl needs to be moved to a position where it can be oxidized
What are the energy capture steps in the CAC?
Steps 3, 4, 5, 6, 8
How is energy captured in steps 3, 4, and 8 of the CAC?
NADH
How is energy captured in step 5 of the CAC?
Substrate level phosphorylation of GDP
How is energy captured in step 6 of the CAC?
FAD
