Another look into Cellular Respiration

Our bodies, as well as other organisms, obtain energy for its life functions through Cellular Respiration. It's pretty much the reverse process of Photosynthesis. Cellular Respiration is the taking our food and breaking it down in the presence of oxygen to make ATP.
ATP is pretty important, seeing as it's usable energy for the cell.

3 basic steps: Glycolysis, The Krebs Cycle (Citric Acid Cycle), and Oxidative Phosphorylation(E.T.C.).

Glycolysis is the only step that doesn't actually occur in the mitochondria, but outside of it in the cytoplasm. During glycolysis, glucose is split in half and some ATP is produced. *Just remember that it happens in an investment phase and a payoff phase. You have to put a little ATP in to get a bigger energy payoff. When glycolysis is finished, you end up with 2 NADH, 2 waters, 2 pyruvates, and 4 ATP. The net energy yield at the end of glycolysis would be 2 ATP and 2 NADH.

The Krebs Cycle occurs in the mitochondrial matrix. In the first series of reactions in the Krebs Cycle , the products from the 2 original pyruvates were 2 carbon dioxides, 2 acetyl coA, and 2 NADH. The first outcome we got was a 6 carbon compound. The second series of reactions left an outcome of a 4 carbon compound, 2 carbon dioxide, and 2 NADH. The third phase of the Krebs cycle will leave us with 1 FADH(subscript 2), 1 NADH, and 1 ATP.
Pretty much at the very end of this cycle you will see that our original 4 carbon molecule is reformed!

Oxidation Phosphorylation or E.T.C. ( Electron Transport Chain),occurs across the inner membrane of the mitochondria. When NADH and FADH(subscript 2) enter the electron transport chain they will give up 2 electrons and 1 proton, so that they will revert back to NAD(plus) and FAD, & go back to glycolysis and through the Krebs cycle to accept more electrons and protons. The E.T.C. creates a concentration gradient, and oxygen is required in order for the E.T.C. to operate. If oxygen isn't available, the Krebs cycle and E.T.C. will shutdown because the gradient disappears, and ATP production is shutdown. * to sum it up, electrons use energy or give energy to proteins to pump protons across the mitochondrial membrane.