Glycolysis and TCA cycle: final accounting
Text – Figures, pg. 584
• based on ~2.5 ATP/NADH and 1.5 ATP/FADH2
• ~32 ATP/(glucose oxidized to 6CO2)
Page 584
Free Energies for TCA Reactions
*
*
*
• note necessity of low (i.e. large negative) DG for
citrate synthase to drive preceding malate
dehydrogenase reaction. This results in low
oxaloacetate concentration.
• large negative DG steps are points of regulation.*
Regulatory Mechanisms in Pyruvate
Dehydrogenase and the TCA Cycle
• covalent modification of enzymes
ex: phosphorylation of pyruvate dehydrogenase
• (non-covalent) product and feedback inhibition
(e.g. by NADH, ATP, citrate)
• allosteric effectors (ADP/ATP, Ca++)
Figure 17-15
Points of
Regulation in the
TCA Cycle
inhibition
activation
Figure 17-16
Text – Figure 17-16
TCA Cycle
intermediates
are a major
source of
molecules for
other
metabolic
pathways
• note that several of the
molecules look like
amino acids, except
for the absence of an
a-amino group
Figure 17-17
Text – Figure 17-17
TCA Cycle intermediates are a major source of
molecules for other metabolic pathways
ex: production of glutamate from aketoglutarate
Page 589
Production of some other amino acids by
transamination reactions
ex: production of alanine and a-ketoglutarate
from glutamate and pyruvate
Production of some other amino acids by
transamination reactions
ex: production of aspartate and pyruvate from
oxaloacetate and alanine
Page 589
The depletion
of TCA cycle
intermediates
for use in other
pathways must
be offset by
replenishing
(anaplerotic)
reactions,
including
pyruvate
carboxylase.
Page 590
Text – Figure, pg. 590