Differences Between Chemosynthesis & Photosynthesis

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  • 0:00 Making Food
  • 0:32 Photosynthesis
  • 1:46 Chemosynthesis
  • 3:15 Lesson Summary
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Lesson Transcript
Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

We all make food in different ways, and the same goes for bacteria, plants, and algae. This lesson goes over the two ways by which such organisms produce food: chemosynthesis and photosynthesis.

Making Food

How do you make food? Well, that depends on who you are, doesn't it? I mean, if you are like me, you just make food by popping it in the oven or microwave. If you're a farmer, you make food by actually growing it before it reaches the supermarket. If you're a professional chef, then you make food with wizardry.

Similarly, many living creatures use different processes for producing food; these processes are generally called photosynthesis and chemosynthesis.

Let's go over their differences and the different organisms that use them.


Photosynthesis is a process by which certain living creatures make sugar and oxygen from carbon dioxide and water with the use of solar energy.

We can actually represent this definition with a nifty formula:

6CO2 + 6H2O -> C6H12O6 + 6O2

All I want you to grasp from this formula is that on the left side we take raw ingredients, carbon dioxide and water, and turn them into our products on the right side, which are carbohydrates (sugars) and oxygen. Like you would need to use heat to bake raw ingredients into a final product, this process happens thanks to energy that's captured by sunlight.

Many living things use this process to make food, including:

  • plants, which provide us with food and oxygen;
  • algae, which serve as a food source for many organisms in the food chain; and
  • some bacteria, such as the green sulfur bacteria.

Furthermore, at least in plants and algae, the process of photosynthesis occurs in organelles called chloroplasts. Think of them as the place where the raw ingredients are cooked, sort of like an oven in our kitchen.

So, to summarize, photosynthesis uses light energy to convert carbon dioxide and water into carbohydrates, which are sugars, and oxygen within organelles called chloroplasts.


Keeping this in mind, let's compare photosynthesis to chemosynthesis. Chemosynthesis is a process whereby a carbon molecule is converted into a sugar-based food source through the oxidation of inorganic molecules as a source of energy.

As just one example of this process, the following formula can be used:

CO2 + 4H2S + O2 -> CH20 + 4S + 3H2O

On the left side, we have our raw ingredients. They are oxygen, a carbon molecule, in this case it's carbon dioxide, and an inorganic molecule, in this case hydrogen sulfide. We mix our ingredients together and they produce a sugar, the CH20, water, and sulfur.

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