Energetic Balance of the oxidation of 1 mol of Pyruvate up to CO2 and water


Answers to Questions about Carbohydrate Metabolism CM-07 and CM-08

 

Answer to (CM-07 )

 

Which is the energetic balance (expressed in moles of ATP) of the total oxidation of 1 mol of Glucose up to CO2 and water, assuming that the Glycolytic Pathway and the Glycerol Phosphate Shuttle have been used.

 

Answer: 36 moles of ATP

 

Note: We are assuming also, as described in the question, that each mol of NADH.H+ oxidized in the respiratory chain yields 3 moles of ATP and each “mol” of FADH2 oxidized in the respiratory chain yields 2 moles of ATP)

 

Details here.

 

 

Answer to CM-08

 

Which is the energetic balance of the oxidation of 1 mol of pyruvate up to CO2 and water?

 

Answer: 15 moles of ATP

 

Note: We are assuming also, as described in the question, that each mol of NADH.H+ oxidized in the respiratory chain yields 3 moles of ATP and each “mol” of FADH2 oxidized in the respiratory chain yields 2 moles of ATP)

 

Details:

 

Oxidative Decarboxylation of Pyruvate occurs in mitochondria, in a reaction catalyzed by the Pyruvate Dehydrogenase Complex.

 

The global reaction is:

Pyruvate +  NAD+ + CoA –à  Acetyl CoA +  CO2 +  NADH.H+ 

 

The resultant Acetyl Co A is oxidized  in the Krebs Cycle yielding:

 

Isocitrate to  alfaketoglutarate  (+CO2)                              1 NADH.H+

alfaketoglutarate to  Succinyl CoA (+CO2)                         1 NADH.H+

Succinyl CoA to Succinate (SLP)                                           1 GTP

Succinate to Fumarate                                                              1 FADH2

Malate to Oxalacetate                                                                1 NADH.H+

 

Observe that at the end of the Kreb Cycle the 3 carbons of pyruvate have been oxidized to 3 CO2

 

At the same time, from the energetic point of view:

1 ATP have been obtained in the Krebs Cycle as GTP through Substrate level Phosphorylation (1 GTP is equivalent, from the energetic point of view,  to 1 ATP).

1 FADH2 have been obtained from the Krebs Cycle

4 NADH.H+ have been obtained inside the mitochondria (1 from Oxidative decarboxylation of Pyruvate and 3 from the Krebs cycle)

 

If we use the convention that each NADHH+ produce approximately 3 ATP in the Respiratory chain, and each FADH2 produce 2 ATP, the total ATP production is:

 

1 Substrate Level Phosphorylation (SLP)                           01 ATP

4 NADH.H+  x 3 ATP/NADH.H                                                12 ATP

1 FADH2  x  2 ATP/FADH2                                                        02 ATP

 Total                                                                                               15 ATP

 

 

 

 

 

 

 

One thought on “Energetic Balance of the oxidation of 1 mol of Pyruvate up to CO2 and water

  1. Pingback: Questions about Energetic Balance in Carbohydrate Metabolism « The Biochemistry Questions Site

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