The gas produced during photosynthesis is oxygen (O2). In this process, plants, algae, and some bacteria convert sunlight, carbon dioxide (CO2), and water (H2O) into glucose and oxygen. Photosynthesis primarily occurs in the chloroplasts of plant cells, where chlorophyll captures light energy, driving the conversion of CO2 and H2O into carbohydrates and releasing oxygen as a byproduct. This essential process not only provides energy for the plants themselves but also contributes to the atmosphere by supplying oxygen, which is vital for the survival of aerobic organisms, including humans.