Prior to entering the Krebs Cycle, each pyruvate molecule loses electrons, hydrogen ions, and a carbon, forming an energy-rich molecule of

a. Acetyl-CoA

b. Citrate

c. Oxaloacetate

d. Malate

a. Acetyl-CoA

Explanation:

Pyruvate is decarboxylated in the matrix of mitochondria and loses its carbon as CO2. This decarboxylation is accompanied by its oxidation as well. This process of oxidative decarboxylation of pyruvate is catalyzed by an enzyme complex. It is called the pyruvate dehydrogenase enzyme complex. NAD + accepts the released electrons and pyruvate is converted into energy-rich acetyl CoA which in turn enters into the Kreb's cycle.