So we have this lactate dehydrogenase is made up of four A chains and it's found in cardiac muscle cells, while the M four, which basically consists of these four individual M isotime chains, makes up the LDH that predominates in skeletal muscle cells. So we see that it's this molecule, the M four, that operates at a maximum efficiency inside skeleton muscle cells where we typically have a lower oxygen concentration. But it's this purple H four LDH molecule that predominates in cardiac muscle cell which operates at a maximum efficiency when there's a high concentration of oxygen, as we typically find in the heart, in the cardiac muscle cell. So these are what isoenzymes are. So isozymes or isoenzymes are these multiple different forms of the same type of enzyme that catalyzes the same type of biochemical reaction that takes place at different locations and ore at different times. Now let's see how we can apply this to our body, to the field of medicine.