Before Citric acid cycle or Krebs cycle, an intermediate reaction takes place which converts the pyruvate into Acetyl CoA. This reaction is known as pyruvate decarboxylation as it produces Carbon dioxide.
Coenzyme A reacts with pyruvate which causes the release of two oxygen atoms and one carbon to form CO₂ along with the reduction of NAD+ to NADH and produce "Acetyl CoA."
