In the light-dependent reactions, light energy is absorbed by chlorophyll and converted into chemical energy in the form of ATP and NADPH. These reactions take place in the thylakoid membranes of chloroplasts and involve the splitting of water molecules to release oxygen gas as a byproduct. The oxygen released comes from the water molecules that are split.
The ATP and NADPH produced in the light-dependent reactions are then used in the Calvin cycle, which takes place in the stroma of the chloroplast. In this cycle, carbon dioxide is fixed and reduced to produce glucose. The Calvin cycle also regenerates the molecules needed for the light-dependent reactions to continue.
Overall, photosynthesis is a complex process that converts light energy into chemical energy in the form of glucose, while also producing oxygen as a byproduct. This process is essential for the survival of plants and most other organisms on Earth, as it provides the food and oxygen needed for life.
The overall equation for photosynthesis is given as:
6 CO_2 + 12 H_2O \rightarrow C_6H_(12)O_6 + 6 H_2O + 6 O_2, with solar energy as the catalyst. This equation shows glucose and oxygen as the products of photosynthesis.
The oxygen given off by photosynthesis comes from water. This was proven experimentally by C.B. van Niel, when he exposed plants first to CO_2 and then to H_2O that contained an isotope of oxygen called heavy oxygen.
The equation also shows that during photosynthesis, CO_2 gains hydrogen atoms and becomes a carbohydrate. The oxidation of any molecule requires energy, and during photosynthesis this energy is provided by the sun.
Two sets of reactions actually contribute to the overall equation for photosynthesis: the light-dependent reactions and the Calvin cycle reactions.
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