How many co2 molecules are generated from each pyruvate that enter the mitochondrion?

In the decarboxylation of Pyruvate to form Acetyl CoA, one Carbon atom is lost as co2.

Acetyl CoA can then be used in the citric acid cycle in which another two co2 molecules are produced.

It is important to note however, that neither Pyruvate nor Acetyl CoA will necessarily follow this pathway, since they are also required for various other processes.