Final answer:
The oxygen produced during oxygenic photosynthesis originates from water (H2O), where it is released as a byproduct during the light reactions. Cyanobacteria were the first organisms to produce oxygen through this process, and chlorophyll is the molecule that absorbs light to drive photosynthesis.
Step-by-step explanation:
The oxygen molecule formed during oxygenic photosynthesis comes from water (H2O), not from carbon dioxide (CO2) or glucose (C6H12O6). During the light reactions of photosynthesis, water molecules split in a process known as photolysis, releasing oxygen as a byproduct. This formation of oxygen is crucial for the survival of aerobic organisms, as it has led to an oxygen-rich atmosphere on Earth.
The first organisms that oxygenated the atmosphere were indeed cyanobacteria, which by using sunlight, water, and carbon dioxide, were able to produce oxygen and glucose. This significant biological development allowed for the evolution of complex, aerobic life forms and the oxygenation of the atmosphere.
Additionally, the primary molecule that absorbs the energy of a photon in photosynthesis is chlorophyll, which is located within the thylakoid membranes of the chloroplasts. With the help of sunlight and chlorophyll, photosynthetic organisms convert carbon dioxide and water into sugars/carbohydrates and release oxygen into the atmosphere, which is a critical sustenance process for life on Earth.