Cellular Respiration
You have chosen to be an Oxygen atom. As your Glucose molecule hangs out in the cytoplasm, you are met by an enzyme. This enzyme performs Glycolysis, splitting your Glucose molecule into two 3-carbon pyruvates. This reaction oxidizes 2 NADH and produces 2 ATP through substrate-level phosphorylation. As an oxygen atom, you continue on with your pyruvate.