fill in the blank. krebs cycle _____ enters the cycle and then combines with _____ to make the six-carbon compound citric acid. this compound then undergoes several reactions which release _____ as waste, _____ and _____ to move onto the next stage of respiration, and energy in the form of _____. a single glucose molecule releases _____ molecules of atp, _____ molecules of nadh, and molecules of fadh2 because two molecules of _____ are created from each molecule of _____ .