In this video, we're going to talk more about the nutritional electron source of microorganisms, and how scientists can classify organisms either as lithotrophs or as organotrophs based on their electron source. Organisms can be categorized into 2 groups based on their electron source. Recall from our previous lesson videos that the electron source refers to the original molecule that supplies electrons to the electron transport chain, or the ETC for short. These two groups that organisms can be classified into are the lithotrophs or the organotrophs. Now, the lithotrophs are going to be organisms that supply their electron transport chain with electrons from reduced inorganic molecules.
Inorganic molecules are going to be molecules that do not contain carbon and hydrogen, such as, for example, water and iron. Neither contain carbon and hydrogen, and so they are inorganic molecules. Many times, these inorganic molecules are going to be found in nonliving substances such as rocks and water itself. It is important to note that all plants are lithotrophs because they harvest electrons from splitting water during carbon fixation. Because they are using water as their electron source, that makes them lithotrophs.
Now, organotrophs, on the other hand, are going to supply their electron transport chain with electrons from organic molecules. Organic molecules are going to be molecules that contain carbon and hydrogen, for example, glucose. If we take a look at our image down below, over here on the left-hand side, what we're showing you are the lithotrophs. The lithotrophs are somewhat like rock eaters in a way because they're going to be obtaining their electrons from inorganic molecules, and inorganic molecules are found in things such as nonliving things such as rocks and water. Here we have a lithotroph saying, "I litho, I mean, I love eating rocks."
Hopefully, that can help you remember that the lithotrophs are going to obtain their electrons from inorganic molecules. Then over here on the right-hand side, what we're showing you are the organotrophs. The organotrophs are going to obtain their electrons from organic molecules that contain carbon and hydrogen such as glucose. Glucose, that sugar, can be found in organics usually found in living substances such as trees, apples, and things like that. Notice that this organotroph is saying, "I only eat organics and obtain electrons from organics."
This here concludes our brief introduction to the electron source as well as lithotrophs and organotrophs. We'll be able to get some practice applying these concepts as we move forward. So, I'll see you all in our next video.
