Why would organisms have different biochemical pathways to metabolize glucose?

Question

I was learning about the MR-VP biochemical test and this question came up.

I did my homework and tried finding out the answer on my own but the info in my textbook and online did not make it clear. (for those who think this is the easy way out)

Answer 1

So that the body can produce ATP in the presence or lack of oxygen

Answer 2

Virtually all organisms metabolize glucose to pyruvate by the same identical pathway of glycolysis. However, different organisms have evolved different ways to ferment pyruvate into different products. The two more common sets of fermentation reactions are formation of lactate and the formation of ethanol and CO2. However, among the zillions of bacteria, a whole mess of different sets of fermentation reactions have evolved, including the pathway that leads to 2,3-butanediol (the pathway detected by the MR-VP test). Remember that main role of the fermentation reactions is to use the electrons generated during glycolysis to regenerate NAD+ so that glycolysis can continue to generate some ATP anaerobically.

Answer 3

Organisms have different biochemical pathways for glycolysis because there are different environments in which glucose metabolism is needed. If there is below-atmospheric oxygen concentration, it doesn't help to have an oxygen-only glycolysis pathway. The same problem occurs if there is no oxygen at all.

If you don't have different methods for glycolysis, then you have no way to produce energy for your cells (ATP). Do your own homework, please.