What are the stages in cellular respiration?

The stages of cellular respiration in eukaryotes include: glycolysis, the TCA cycle, and oxidative phosphorylation. 

1. Glycolysis is an anaerobic and aerobic pathway and occurs within the cytoplasm of cells; this pathway catalyzes 1 glucose molecule and generates 2 pyruvate molecules, 2 ATP, water and 2 NADH. Glucose is broken down by different enzymes to produce energy for cells. Glycolysis involves 2 phases; the investment phase and the payoff phase. The investment phase requires 2 ATP molecules per glucose sugar. The payoff phase releases 4 ATP molecules of energy, netting a total of 2 ATP in the entire process. 
2. The TCA cycle involves various reactions in which 2 carbon atoms of acetyl-CoA are oxidized to CO2. The energy stored within the two atoms is then converted to NAD+ and FAD, resulting in NADH and FADH2. Each molecule of glucose generates 2 pyruvate molecules and thus the TCA cycle must be completed twice to entirely break down the original glucose molecule. At the end of the TCA cycle, the molecules formed are 2 ATP, 8 NADH, 2 FADH, and 6 CO. Oxidative phosphorylation involves 2 sub-processes: the ETC and chemiosmosis. 
3. In the ETC, electrons carried by NADH and FADH2 are released; these electrons travel through a series of molecules within the inner mitochondrial membrane. As electrons move along the ETC, some of their energy is utilized to drive hydrogen ions across the inner membrane, specifically from the matrix into the intermembrane. This pumping of ions forms an electrochemical gradient which fuels the generation of ATP.  The electrochemical gradient formed causes ions to flow back across the membrane into the matrix where they are less concentrated. This movement occurs through the ATP synthase complex. ATP synthase functions as a channel protein to assist in transporting ions across the membrane. This transport of ions via ATP synthase is known as chemiosmosis. ATP synthase also functions as an enzyme producing ATP from ADP and inorganic phosphate. Following passage through the ETC, oxygen (the final electron acceptor of the ETT) is reduced to water and is used to help clear the mitochondrial chain of low-energy electrons.