And so they essentially inhibit or block the activity of that enzyme. Now, there are many different examples of Irreversible inhibitors and three examples are listed on the board. So we have nerve gas, we have penicillin, and we have aspirin. And each one of these molecules basically binds to inhibits a specific type of enzyme found inside our body. So let's begin with nerve gas. Nerve gas is a very dangerous, very potent Irreversible inhibitor and it forms covalent bonds.