So inside our body, when the cells of our body don't have enough oxygen, they will take the pyruvates and transform them into lactic acid molecules. Now, what happens if there is oxygen present in the cells of our body? Well, in the case of aerobic conditions, when we have oxygen present in the cell, the Pyruvate molecules will move into the mitochondria of the cell. And so this is our mitochondria. And inside the mitochondria, we have processes such as Pyruvate decarboxylation as well as the citric acid cycle and the electron transport chain found on the inner membrane of that mitochondria actually uses those oxygen molecules to ultimately transform the Pyruvate into carbon dioxide molecules as well as ATP molecules. In fact, the majority of ATP molecules produced by our cells are formed in the process that takes place inside the mitochondria.