At first glance, fermentation of pyruvate to lactate appears to be an optional add-on reaction to glycolysis. After all, could cells growing in the absence of oxygen not simply discard pyruvate as a waste product? In the absence of fermentation, which products derived from glycolysis would accumulate in cells under anaerobic conditions? Could the metabolism of glucose via the glycoll'tic pathway continue in the absence of oxygen in cells that cannot carry out fermentation?\.A/hy or why not?

Glycolysis includes ten sequential steps which can be divided into two separate phases:preparatory phase and pay off phase
In preparatory phase glucose is phosphorylated in 6th and 1st carbon and then cleaved in 3-C sugar;2 ATP gets consumed in this phase
In pay off phase 3-C sugar is sequentially oxidized to yield ATP, NADH and pyruvate

Fermentation is exclusively operated in absence of oxygen

Fermentation is basically an energy yielding metabolic reaction in which final electron acceptor is an internal organic molecule(an intermediate of metabolic reaction)
There are two type of fermentation:alcoholic and lactic acid fermentation
In alcoholic fermentation pyruvate gets converted into acetaldehyde (by pyruvate decarboxylase) which further gets converted into ethanol
In lactic acid fermentation pyruvate is the final electron acceptor and gets converted into lactate;reaction catalyzed by lactate dehydrogenase

Glycolysis can continue in the absence of oxygen, but only in cells that can carry out fermentation because under low oxygen or no oxygen NADH cannot be reoxidized to NAD+,NAD+ is required as an electron acceptor to continue glycolysis