In this video, we're going to begin our lesson on reactive oxygen species. Aerobes, which you recall from our previous lesson videos are microbes that require oxygen gas, tend to generate toxic derivatives of oxygen called reactive oxygen species. Reactive oxygen species are commonly abbreviated as just ROS. Reactive oxygen species, or ROS, are highly reactive oxygen molecules that can cause damage to the cell. Reactive oxygen species, or ROS, present a problem for aerobes. Examples of reactive oxygen species, or ROS, include superoxide, which is O₂^-, as well as hydrogen peroxide, which is H₂O₂. Superoxide and hydrogen peroxide are capable of causing damage to the cell. These aerobes need to have a way to manage these reactive oxygen species, and all aerobes produce enzymes that protect the cell from these reactive oxygen species, or ROS.

Here, what we're showing you are three enzymes that these aerobes can use to protect themselves from the reactive oxygen species. The first enzyme that we have here is superoxide dismutase, abbreviated as SOD. This enzyme converts two superoxide molecules into oxygen gas and hydrogen peroxide. If we take a look at our image down below, reactive oxygen species, or ROS, include oxygen, O₂^-, which is superoxide, as well as hydrogen peroxide or H₂O₂. Once again, these can cause damage to the cell. These three enzymes help to protect the aerobes from these reactive oxygen species.

Superoxide dismutase converts two superoxide molecules, or two O₂^- molecules, and converts them with hydrogen ions into hydrogen peroxide and oxygen gas. The next enzyme is catalase. Catalase converts two hydrogen peroxide molecules into oxygen gas and two molecules of water. Notice that catalase converts two hydrogen peroxide molecules into two water molecules and oxygen gas. Water and oxygen gas are non-toxic to aerobes. By using these enzymes, aerobes are able to convert toxic reactive oxygen species into non-toxic components.

Sometimes, they need to work together to convert these toxic components, these toxic reactive oxygen species, into non-toxic molecules of water and oxygen gas. The third and final enzyme that we're going to talk about here is peroxidase. Peroxidase converts hydrogen peroxide, and two hydrogen ions, into two water molecules. Again, converting toxic reactive oxygen species into non-toxic components such as water and oxygen. This concludes our brief lesson on reactive oxygen species, these toxic components that tend to be generated by aerobes, and the enzymes that aerobes use to protect themselves from their own reactive oxygen species that they generate. We'll be able to get some practice applying these concepts as we move forward in our course. I'll see you all in our next video.