A Meeting with Mr. Mitchell

Although aerobic metabolism and photosynthesis are two different metabolic pathways used to obtain the energy for ATP phosphorylation, they share many similarities and structures. The harnessing of the chemiosmotic gradient is perhaps the most important; it is this moment, when the ATP synthase is activated and allows the protons to leave the acidic region, that results in the phosphorylation energy. In aerobic metabolism, the intermembrane space becomes acidic because of the cytochromes pumping protons and moving electrons down the chain. Oxygen is essential in this electron transport chain because it is the terminal electron acceptor and prevents pyruvate, the product of glycolysis used in the preceding Krebs cycle, from building up. Pyruvate is a toxin which means oxygen is crucial for the organism to survive. Photosynthesis occurs in the chloroplast, which is why it can only happen in plants, but aerobic metabolism occurs in the mitochondrion which allows it to happen in every organism except bacteria.