Lecture 16 - Citric Acid Cycle 3 Flashcards
(15 cards)
What is the product of reverse transamination of pyruvate
Alanine
What is the product of reverse transamination of OAA
Aspartic Acid
How much ATP is generated per glucose in glycolysis
7
How much ATP does the average 70kg Human have
50g
What is the typical rate of ATP synthesis per day
10^21 ATP per second
a human uses their body weight in ATP per day
So each ATP is broken down and resynthesized about 1500 times a day
How is PDHC regulated
allosterically
ATP and the products acetyl-CoA and NADH, inhibit the complex
AMP, CoA and NAD+ activate the complex
How is PDHC regulated in mammals
Phosphorylation status mainly§
Where are the key site for regulation to occur in the CAC and why
Reactions that occur with large free energy changes
citrate synthase
isocitrate dehydrogenase
2-oxoglutarate dehydrogenase
What is a key factor in regulating CAC
Ratio of NAD+ to NADH
NAD+ conc can limit dehydrogenase enzymes
What is another regulation factor besides NAD+:NADH
Citrate
High citrate inhibits citrate synthase
(Remember that citrate also regulates glycolysis [PFK])
NOT A MAJOR SITE FOR REGULATION
How is isocitrate dhydrogenase regulated
Allosterically activated by ADP
Allosterically inhibited by NADH and ATP
How is 2-oxoglutarate dehydrogenase
regulated
Inhibited by accumulation of its products, succinyl-CoA and NADH
How are both isocitrate dehydrogenase and 2-oxoglutarate dehydrogenase stimulated
Calcium 2+ ions
same as PDHC
What are anaplerotic reactions
derived from Greek and meaning ‘filling up
As some intermediates of CAC are removed for other purposes, there is some topping up required
eg. producing OAA from pyruvate and pyruvate carboxylase
How does Pyruvate carboxylase activity work
PDHC is less active when acetyl-CoA is high
Pyruvate carboxylase is stimulated by acetyl-CoA
This regulates whether pyruvate goes to acetyl-CoA or is carboxylated
