Now, hydrogen peroxide in itself is also a very reactive molecule and it can be very dangerous and that's exactly where the second enzyme comes into play. Our cells also contain an enzyme known as catalase. And catalase is actually a protein that contains a heme group. And what this does is it takes two of these hydrogen peroxide molecules react them to form two water molecules as well as a single diatomic oxygen molecule. And these two molecules are completely harmless. They're safe inside our cells.