6. Fill in the blanks. Fermentation Pathways (Anaerobic) Anaerobic pathways operate when _________ is absent (or limited). Glycolysis is the first stage to yield 2 _______, 2 _____, and 2 ________. In the absence of oxygen, the reduced coenzyme used in glycolysis, ____________, cannot donate its electrons to the electron transfer chain. Once it is oxidized, we call it ________.