Back to: MICROBIOLOGY 200 LEVEL
Welcome to class!
Hello my bright star! I’m so happy you’re here, ready to learn again. Your hunger for knowledge makes you truly special. Today’s topic is one of those that shows us just how diverse and brilliant nature can be—it’s all about Oxygenic vs. Anoxygenic Photosynthesis. Don’t worry about the big terms—we’ll break it down together in a way that’s as relatable as talking to your best friend about Nigerian weather or plantain and beans!
Oxygenic Vs. Anoxygenic Photosynthesis
What is Photosynthesis?
Photosynthesis is the process by which organisms make their own food using light energy, usually from the sun. You already know plants do this, right? But guess what—microorganisms can also photosynthesise! And depending on how they do it, we classify it into two main types: oxygenic and anoxygenic photosynthesis.
Let’s see what makes them different.
Oxygenic Photosynthesis
This is the common type of photosynthesis you know, carried out by:
Green plants
Algae
Cyanobacteria (a type of bacteria found in ponds, rivers, even rice paddies)
In this type:
Water (H₂O) is used as the electron donor.
When sunlight hits, water is split into oxygen, protons, and electrons.
The oxygen is released into the atmosphere. That’s the air we breathe—thank you, photosynthesis!
This is why it’s called oxygenic—because it produces oxygen.
Equation:
6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ (glucose) + 6O₂
Anoxygenic Photosynthesis
Now, this type is a bit different and happens mostly in certain bacteria, like:
Purple sulphur bacteria
Green sulphur bacteria
Some heliobacteria
Here’s the twist:
Instead of water, they use other substances like hydrogen sulphide (H₂S) as the electron donor.
Because they don’t split water, oxygen is not produced.
That’s why it’s called anoxygenic—no oxygen is formed.
These organisms are usually found in places where there is light but no oxygen, like swamps, hot springs, or muddy riverbanks.
Imagine two types of suya spots in Nigeria. One uses charcoal (like oxygenic photosynthesis uses water), and the other uses firewood and palm kernel shells (like anoxygenic photosynthesis uses H₂S). Both roast meat, but the smoke and flavour are different. In the same way, both types of photosynthesis produce energy, but they use different fuel and give different by-products.
Why Does It Matter?
Oxygenic photosynthesis adds oxygen to the atmosphere, which supports most life on Earth.
Anoxygenic photosynthesis is older—it was probably the way early bacteria survived before oxygen became common.
Studying these helps us understand evolution, climate cycles, and even how life might exist on other planets!
Summary
- Oxygenic photosynthesis produces oxygen and uses water as the electron donor.
- Anoxygenic photosynthesis does not produce oxygen and uses other compounds like hydrogen sulphide.
- The two types occur in different organisms and environments.
- Both are vital to ecosystems and our understanding of life.
Evaluation
- What is the main difference between oxygenic and anoxygenic photosynthesis?
- Name one organism that performs anoxygenic photosynthesis.
- Why is oxygen not produced in anoxygenic photosynthesis?
- How is water used in oxygenic photosynthesis?
Well done, champion! You’ve just added a powerful piece of science knowledge to your brain-bank. Keep up the fantastic work—you’re getting stronger and smarter with every lesson. With Afrilearn, you’re not just learning; you’re preparing to change the world. Let’s keep shining together! See you in the next class!