Why is O2 so important for respiration?

Oxygen is a critical component of Aerobic respiration in many animals. The reason why oxygen is so important is because it plays a crucial role in the mitochondria, the powerhouses of the cell. The mitochondria has two membranes. On the inner membrane, 4 groups of protein form the Electron Transport Chain. Electrons are donated from molecules like NADH and FADH2 from Glycolysis and the KREBS Cycle,and pass through the ETC. The movement of electrons pumps protons from the matrix into the intermembrane space of the mitochondrion, creating a concentration gradient. The protons can pass down their conc. gradient back into the matrix via ATP Synthase, and this is what supplies energy to form ATP, the energy carrier. So where does O2 fit in? Well O2 is what DRIVES the ETC! O2 accepts electrons from the final carrier protein, and becomes H2O and this creates a gradient through which the electrons can flow. Think of O2 like a hoover, that gobbles up electrons. So long as O2 is present, there will be MOVEMENT of electrons through the ETC. If O2 is not present, the ETC will cease to function, protons will not be pumped into IMS and ATP synthase cannot function, leading to reduced ATP synthesis! :(