The first stage is Glycolsis, which works anaerobicly and occurs in the Sarcoplasm (the cytoplasm of a muscle). This process happens happens in 10 stages where various, slight but important changes are made. In this process 4 ATP molecules are produced but 2 are used in the breakdown of glucose leaving a net gain of 2. Glucose is split to from 2 3-carbon sugars, which is then oxidised to form Pyruvate. At this point aerobic respiration meets anerobic respiration. The pyruvic acid is oxidised forming Acetyl Co A, a 2 carbon compound that can enter the kreb cycle. In this cycle Acetyl Co A combines with Oxaloacetic acid to form citric acid, a 6 carbon compound. This releases carbon dioxide which can be safely breathed out, it resynthesises a further 2 ATP and releases hydrogen which is taken by NAD to the electron transfer chain in the Mitochchondria. The electron transfer chain occurs in the Cristae of the Mitochondria (where the enzymes and proteins for this chain are attached to the inner wall). NAD and FAD combine with the hydrogen ions made during glycolsis to make NADH and FADH. They then donate electrons to the first carrier molecule of the electron transfer chain. The electrons pass through the chain by a series of redox (reduction and oxidation) reactions. The energy from the electrons and the hydrogen powers ATPsynthase which uses ADP and phosphate to resynthesise ATP. At the end of this chain electrons combine with protons and Oxygen to form water.