We oxidize our macromolecules such as sugars, lipids, and proteins. Now, the final way by which we can categorize organisms is by the source of electrons. So those organisms that basically obtain their electrons form organic materials such as sugars, proteins, or lipids. And this includes us humans. These types of organisms are known as organotropes, while those organisms that obtain their electron source from non organic or inorganic materials, those are known as lithotrophs. So basically, we have the source by which we obtain our carbon.