wellnow wrote:
spaniel, what are you blathering on about? for goodness sake learn some physiology and drop the fizzyology
you wrote: "Lactate is a reporter of the level of anaerobic metabolism that is occurring"
No it isn't, lactate is an inevitable product of carbohydrate metabolism.
"Anaerobic metabolism is terribly inefficient compared to aerobic metabolism, and therefore not nearly as sustainable.
Again you are reporting an outdated idea. The glycolytic ATP that accompanies lactate production provides a non-mitochondrial fuel source, whilst the lactate provides a aerobic fuel source from mitochondrial respiration. The ATP counts for glycolytic ATP are lower overall because there is much less of it produced, not because it is an inneficient fuel source. But it can supply energy for short bursts much more quickly than aerobic respiration.
OK, I'll use smaller words so you are capable of understanding.
Lactate is NOT an "inevitable" product. That would mean it HAS to be produced. If this were true, pyruvate would not be produced and shuttled to the mitochondria for aerobic respiration. A reporter is something that can be measured that is an accurate measure of some other activity. Since the pathway producing lactate is anaerobic glycolysis, lactate is an accurate reporter of the proportion of energy being derived from this pathway.
Lactate does NOT provide an aerobic fuel source in the same way that pyruvate does. Sure, the body recycles it later as it does everything but it is a much slower process. This data is not outdated.
J Physiol. 2007 Aug 1;582(Pt 3):1317-35. Epub 2007 Jun 7.
2007 is recent evidence, is it not?
It is inefficient because when you arrive at the end product, lactate, much of the glucose molecule's potential energy is left locked up by the lactate. Conversely, when oxygen is used, pyruvate is broken all the way down to CO2 resulting in roughly 85% efficient conversion into energy as ATP.
Yes, it can supply energy at a faster rate for short bursts. This is correct. Fewer steps, and does not require translocation of pyruvate to the mitochondria. However because it is faster it burns through available fuel much faster, and is not sustainable.
If your argument was correct, why would two pathways exist if they end up the same place? What is the difference? Aerobic respiration goes through glycolysis as well. The anaerobic process exists because it is faster and allows that short burst, but you pay in that it is not sustainable.
Perhaps you think I'm blathering because you read a couple journal articles and deluded Richard's posts and think you actually comprehend or know something. In reality, you lack the deeper understanding of metabolic biochemistry that allows one to link all of these separate pathways and how they affect each other. I on the other hand am trained as a cellular and molecular biologist, so I have that background. Come back and play when you are more than an internet wannabe "expert".