The oxygen in photosynthesis is released from:
- H₂O (Water)
Photosynthesis is the process by which plants, algae, and some bacteria convert sunlight, carbon dioxide (CO₂), and water (H₂O) into glucose (carbohydrate) and oxygen (O₂). The oxygen released during photosynthesis is derived from water molecules.
Here is a detailed explanation of the process:
1. Light Energy Absorption:
- Chlorophyll, a pigment found in chloroplasts of plant cells, absorbs light energy from the sun.
2. Splitting of Water Molecules:
- This light energy is used to split water molecules (H₂O) into hydrogen ions (H+) and oxygen (O₂) atoms through a process called photolysis.
3. Electron Transport Chain:
- The hydrogen ions generated from the splitting of water are used in the electron transport chain to produce energy-rich molecules such as ATP (adenosine triphosphate) and NADPH (nicotinamide adenine dinucleotide phosphate).
4. Carbon Dioxide Fixation:
- Carbon dioxide (CO₂) from the atmosphere enters the plant through small openings called stomata and is converted into glucose through a series of enzymatic reactions known as the Calvin cycle.
5. Release of Oxygen:
- As water is split during photosynthesis, oxygen atoms are released into the atmosphere as a byproduct. This oxygen is the same oxygen that we breathe.
Thus, the oxygen released during photosynthesis is derived from the water molecule (H₂O) and not from carbon dioxide (CO₂), carbohydrate, or chlorophyll.

The splitting of water molecules during the light-dependent reactions of photosynthesis.