27. what is the major reactant needed for the citric acid cycle (aka krebs cycle)?
a. pyruvate
c. chlorophyll a
b. acetyl co-a
d. water

b. Acetyl Co-A

Explanation:

Acetyl CoA produced through pyruvate, amino acids, and fatty acids are oxidized in the Krebs cycle in CO2, obtaining as products NADH, FADH2 and GTP (ATP). Parallel to this oxidation, the Krebs cycle produces compounds used as precursors for biosynthesis. As it is a cycle, an oxaloacetate molecule could, in principle, oxidize an amount indefinite of acetyl CoA. Acetyl-CoA is formed from the oxidative decarboxylation of pyruvate, sequentially performed by pyruvate dehydrogenase -PDH (complex multi enzymatic of 3 enzymes), in the mitochondrial matrix.

not sure if this is what you'r looking for eubacteria and archaebacteria