Gluconeogenesis vs. Cori Cycle

[Gauss44]

Let's see if I have this right:

Lactate is transformed to pyruvate, and pyruvate to glucose.

The lactate to pyruvate part is NOT considered part of gluconeogenesis? Gluconeogenesis begins with pyruvate being converted to oxoloacetate (which is then converted to glucose)?

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[Czarcasm]

Let's see if I have this right:

Lactate is transformed to pyruvate, and pyruvate to glucose.

The lactate to pyruvate part is NOT considered part of gluconeogenesis? Gluconeogenesis begins with pyruvate being converted to oxoloacetate (which is then converted to glucose)?

Yep. The end product of Glycolysis is 2 Pyruvate molecules, where as Gluconeogenesis begins with 2 Pyruvate molecules to make Glucose. It might help to think of it as the reverse of Glycolysis (although that's not exactly true). The key difference is there's 11 steps in Gluconeogenesis and also, (4) unique/different enzymes are needed for each of the 3 commited steps in Glycolysis (since those enzymes only act in 1 direction).

Cori Cycle encompasses both cycles: Glycolysis and Gluconeogenesis, although they are occurring in different cells at the same time.

 

[Gauss44]

Yep. The end product of Glycolysis is 2 Pyruvate molecules, where as Gluconeogenesis begins with 2 Pyruvate molecules to make Glucose. It might help to think of it as the reverse of Glycolysis (although that's not exactly true). The key difference is there's 11 steps in Gluconeogenesis and also, (4) unique/different enzymes are needed for each of the 3 commited steps in Glycolysis (since those enzymes only act in 1 direction).

Cori Cycle encompasses both cycles: Glycolysis and Gluconeogenesis, although they are occurring in different cells at the same time.

Thanks, now what I read somewhere in the context of the Cori Cycle, which transforms lactate back into glucose, is that the "gluconeogenesis" part of that cycle actually begins with pyruvate, and not lactate. Is that correct? I'm not sure if the author of that article misspoke, or if it's correct.

 

[Czarcasm]

Thanks, now what I read somewhere in the context of the Cori Cycle, which transforms lactate back into glucose, is that the "gluconeogenesis" part of that cycle actually begins with pyruvate, and not lactate. Is that correct? I'm not sure if the author of that article misspoke, or if it's correct.

Lactate is converted to Pyruvate via lactate dehydrogenase, so that pyruvate can enter gluconeogenesis. So for instance, a muscle cell is constantly undergoing Glycolysis, runs out of O2 supply, produces Lactate via Fermentation (to regenerate NAD+). The excess lactate travels through the blood, picked up by the liver, is converted to pyruvate and that pyruvate is converted to Glucose which can than be stored and released as needed. This collectively is the Cori Cycle.