Glucose

Glycolysis is not a simple process. While one might think glucose would be a main energy source for the cell, it isn't. It is, however, a great way to generate the main energy source of cells, ATP. Glucose must first be broken down into pyruvate. In this process,some ATP is used, but there is a net gain of 2 ATP molecules. Pyruvate can then go on to fuel the citric acid cycle, which causes the build up of NADH, and 2 FADH molecules. these molecules go on to create many more ATP molecules in the electron transport chain. One glucose molecule can eventually become 32 molecules of ATP via these three processes. That's a lot of energy.