The reactants of photosynthesis are water, carbon dioxide and light energy. Plants use these reactants to make the food that is essential for plant growth.
The chemical reaction of water and carbon dioxide in the presence of energy from sunlight creates glucose. Some of the glucose is used by the plant for food, while some is stored for later use. Stored glucose is consumed by animals when they eat the plant. Oxygen is produced as a byproduct of photosynthesis and is released into the air to be used in the process of cellular respiration.
Photosynthesis occurs in a plant's chloroplasts, where chlorophyll collects energy from sunlight to begin the chemical reaction between water and carbon dioxide.