Number of ATP consumed during gluconeogenesis?

[whatdidigetinto]

In Rapid review pathology it states that 6 ATP are need to produce one molucle of glucose through gluconeogenesis.

Now 2 pyruvate are needed to make 1 glucose molecule in guconeogenesis.
Pyruvate carboxylase uses 1 ATP,
PEP carboxykinase uses 1 ATP.

Considering two molecules of pyruvate are needed, we should multiply the steps above by 2.
That gives us a total of 4 ATP used.

Where are the other 2 ATP used? what am i missing?

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[Myxedema]

You're right, 2 ATP and 2 GTP are used.

Can you tell the page number in RR Pathology?

 

[Phloston]

Firstly, GTP, not ATP, is used by PEP carboxykinase (but yes, 2 GTP = 2 ATP equivalents).

Secondly, phosphoglycerate kinase, which converts 3-phosphoglycerate into 1,3-bisphosphoglycerate, requires ATP.

So:

2 x pyruvate --> oxaloacetate (= 2 ATP)
2 x oxaloacetate --> PEP (= 2 GTP)
2 x 3-phosphoglycerate into 1,3-bisphosphoglycerate (= 2 ATP)
-------
= 6 ATP equivalents

 

[whatdidigetinto]

Thanks, i was just focusing on the irreversible enzymes in my calculations, i totally forgot about the rest!