Krebs cycle?

["Beth Glace" <lb@nismat.org>]

Tom wrote:

<You really don't want to know. It's the oxidative energy pathway 
that takes place within the mitochondria within and around the muscle 
cell (and other organs). There are several metabolic steps involved, 
each requiring energy and time, in converting fatty acids to ATP 
(immediate energy source)..............The result is Acetyl-CoA, 
which can then enter the Krebs cycle for a series of electron 
transport reactions to generate ATP molecules. 

The sequence produces a lot of energy, but it is slow. Cow slow.>>>

Tom, 
while it is slower, than glycolysis  it represents AEROBIC metabolism 
and has to be seen as the prime mechanism by which energy is 
generated in events lasting more than a few minutes.  You kind of 
implied [do I misinterpret?] that we want to try to stay away from 
this pathway and that only fats use this pathway????  Lif, carbs 
begin their energetic pathway as glucose is converted to pyruvate 
[=glycolysis].  This series of steps can happen quickly but does not 
produce very much energy.  If oxygen is available, the pyruvate is 
converted to acetyl CoA and enters the Krebs cycle.  If no oxygen is 
available or this is all happening in fast twitch fibers, the 
pyruvate will be converted into lactic acid, making for anaerobic 
metabolism ["no oxygen needed"]. So, both CARBS & FATS  
go through the Krebs cycle in aerobic metabolism, and if they weren't 
you would be making lots  lactic acid!    A self limiting process.  
Carb utilization for only glycolysis is not primarily what is 
happening in endurance. 

Beth


Beth Glace, MS, CDN
Nicholas Institute of Sports Medicine and Athletic Trauma
Lenox Hill Hospital
New York, NY


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