Answer:Decarboxylation, the Reduction of NAD+, and the attachment of CoA.
Step-by-step explanation:
Step 1 Decarboxylation: the co-enzyme thiamine pyrophosphate (TPP) catalyzes the decarboxylation of the carboxyl group of pyruvate and given off as a molecule of CO2. The two carbon unit remains attached to the enzyme.
Step 2 Reduction: The remaining two-carbon (hydroxyethyl group) is oxidized to form acetyl group. The extracted electrons are transferred to NAD+, storing energy in the form of NADH.
Step 3. The last step is the attachment of coenzyme A, a sulfur compound derived from a B vitamin, is attached to the acetyl group to form acetyl CoA, the Co-enzymes TPP, Lipoamide and FAD will be regenerated.
The acetyl CoA will go into TCA for complete oxidation.