The main gas released during photosynthesis is oxygen (O2). This process occurs in plants, algae, and some bacteria, where they convert carbon dioxide and water into glucose and oxygen using sunlight as energy. During photosynthesis, chlorophyll in the chloroplasts captures sunlight, driving the chemical reactions that split water molecules and release oxygen as a byproduct. Oxygen is essential for the survival of many organisms, including humans, as it is vital for cellular respiration. Photosynthesis not only provides oxygen but also forms the foundation of the food chain by producing energy-rich carbohydrates.