We go from a six carbon molecule to a five carbon molecule known as alpha keto gluterate. Now, once we form the alpha ketoglutrate, that further undergoes a decarboxylation reaction. So we release yet another carbon dioxide. So that means we go from a five carbon to a four carbon molecule known as succinctal coenzyme A. Now, the coenzyme A release in step one reacts with this molecule and goes into the process. That's why we have the succinl coenzyme A, and we also once again, reduce an NAD into our NADH.