Microbiology, part 19: Metabolism - Carbon and Energy Source

Hi, I'm Cathy with Level Up RN. In this video, we'll be discussing how to classify an organism based on their carbon and energy source. At the end of the video, I'm going to give you guys a quiz to test your understanding of some of the key information I'll be covering, so definitely stay tuned for that. And if you have our microbiology flashcards, go ahead and pull out your flashcard on carbon and energy source so you can follow along with me.

In order to carry out metabolism, organisms need a source of energy and a source of carbon. Phototrophs are organisms that obtain energy from the sunlight, so the prefix photo means light. Chemotrophs are organisms that obtain energy from the breakdown of chemical compounds. The prefix chemo means chemical. In terms of carbon source, an autotroph obtains carbon from carbon dioxide. It does this by converting inorganic carbon dioxide molecules into organic glucose molecules. The prefix auto means self, so an autotroph can make its own food by itself. This is different than a heterotroph, which cannot make its own food and needs to obtain carbon from other organisms. So the prefix hetero means different or other. So a heterotroph relies on others for its carbon. Our cool chicken hint to help you remember the difference between an autotroph and heterotroph is that an autotroph can make its own food, whereas a heterotroph needs to mooch off of others.

So if we put together an organism's energy source and carbon source, we get photoautotrophs, photoheterotrophs, chemoautotrophs, and chemoheterotrophs. Examples of photoautotrophs include plants and algae, which are organisms that carry out photosynthesis. During photosynthesis, the energy from the sunlight is used to convert carbon dioxide and water into sugar molecules. Examples of organisms that are photoheterotrophs include green and purple sulfur bacteria. Examples of chemoautotrophs include organisms that live in extreme environments, such as methanogens and halophiles. And then an example of a chemoheterotroph is a human. We obtain our carbon by eating organic compounds such as plants or animals, and then we obtain our energy through the breakdown of those chemical compounds during cellular respiration.

All right. It's quiz time. And in this particular quiz, the answer to each question will either be photoautotroph, photoheterotroph, chemoautotroph, or chemoheterotroph. You guys ready? Number one. What do you call an organism that obtains carbon by ingesting other organisms, and obtains energy through the breakdown of chemical compounds? The answer is a chemoheterotroph. Number two. What do you call an organism that carries out photosynthesis? The answer is a photoautotroph. And number three. What do you call an organism that obtains energy from the sunlight, and obtains carbon from other organisms? The answer is a photoheterotroph. All right. That's it for this video. I hope it was helpful. And I hope you enjoy the blooper reel, which is coming up next.

[BLOOPERS]

So if we put an organism's energy and carbon source together, we get photoautotrophs, photoheterotrophs. Photo-photo-photo-photo-- [inaudible]. Photoheterotrophs, [autochemophototrophs?]. Oh my god. Photoheterotroph, c-- chemoautotroph or [chemoeder-ederotroph?]. Whatever that is. Oh my god. This video's cursed.