In this video, we're going to talk about the nutritional carbon source of microorganisms, and how scientists can classify organisms either as heterotrophs or autotrophs depending on the carbon source. Microorganisms are classified into two groups based on their source of carbon and whether that carbon source is organic or inorganic. Recall that "organic" just means that the substance contains both carbon and hydrogen, whereas "inorganic" means that it does not contain both carbon and hydrogen. The carbon source itself refers to the original carbon-based molecule that supplies carbon to the cell so that the cell can use that carbon to create other cell components. Autotrophs use carbon fixation to capture carbon and make their own food and other cell components.
Autotrophs make their own food, usually fixating inorganic carbon such as carbon dioxide. Heterotrophs, on the other hand, consume rather than make their own food, using organic molecules that supply the carbon needed to create other cell components. Focusing on the image below on the left hand side, we see autotrophs making their own food by using carbon fixation to capture inorganic carbon, such as carbon dioxide. They fix carbon dioxide to supply their carbon, demonstrating how autotrophs that are able to perform photosynthesis and carbon fixation fix inorganic carbon. On the right hand side, we show heterotrophs. For example, a heterotroph could be a bunny rabbit.
This bunny rabbit must consume organic molecules to supply its cells with carbon. Notice that this bunny rabbit, the heterotroph, is eating the autotroph, which is the carrot. Thus, the carrot is the autotroph, and the bunny rabbit is the heterotroph. This concludes our brief introduction to the carbon source, heterotrophs, and autotrophs. We will be able to get some practice applying these concepts as we move forward.
So, I'll see you all in our next video.