Long before animal life appeared on the Earth, the plants were busy making food for them. By the wonders of a pigment known as chlorophyll, the plants took a simple gas called carbon dioxide and water, then borrowed energy from the sun and made a food called sugar. Sugar is a molecule consisting of carbon, oxygen and hydrogen held together by strong chemical bonds forged in the cell leaf, with ATP generated in the leaf using photons from the sun’s light.
Chloroplasts are organelles found in plant cells that conduct photosynthesis. They capture light energy and convert it to a form of ATP through photosynthesis, which occurs in several steps. Some of the light energy is stored in the form of ATP while most of it is used to remove electrons from water. These electrons are then used in the reactions that turn carbon dioxide into the organic compound know as sugar, actually sucrose. The plant achieves this by a sequence of reactions known as the Calvin cycle.