True/False Photosynthesis always results in the formation of oxygen.
The correct answer and explanation is:
False
While the most commonly taught and observed form of photosynthesis, performed by plants, algae, and cyanobacteria, does produce oxygen as a byproduct, this is not universally true for all types of photosynthesis.
This standard form, known as oxygenic photosynthesis, uses water (H₂O) as the primary electron donor. Light energy is used to split the water molecule (a process called photolysis), releasing electrons that enter the photosynthetic electron transport chain. This splitting of water also yields protons and, crucially, oxygen gas (O₂), which is released into the atmosphere.
However, there are other forms of photosynthesis carried out by certain bacteria, collectively known as anoxygenic photosynthesis. Organisms like purple sulfur bacteria, green sulfur bacteria, and heliobacteria perform this type of photosynthesis. Instead of using water as their electron source, they utilize other reduced compounds such as hydrogen sulfide (H₂S), elemental sulfur (S), hydrogen gas (H₂), or even organic molecules.
Since the oxygen produced in oxygenic photosynthesis comes specifically from the splitting of water, and these anoxygenic bacteria do not use water as their electron donor in this way, they do not produce oxygen as a byproduct of their photosynthetic process. Therefore, the statement that photosynthesis always results in the formation of oxygen is incorrect.