Photosynthetic organisms use light energy from the sun to transform two reactants, carbon dioxide and water, into sugar and oxygen gas. Green plants, algae and some bacteria can perform photosynthesis and are responsible for oxygenating the Earth's atmosphere.
Light energy transforms six carbon dioxide molecules and six water molecules into one molecule of glucose (sugar) and six molecules of oxygen gas.
Comsumption Vs. Production
In a chemical reaction, reactants are chemical compounds that are consumed or transformed to make the products. Thus, carbon dioxide and water are the reactants in photosynthesis, and glucose and oxygen are the products.
Photosynthesis and cellular respiration are complementary reactions. Cellular respiration is the process by which most cells make energy. The products of photosynthesis, oxygen and glucose, are the reactants of the cellular respiration reaction. In turn, the products of cellular respiration, carbon dioxide and water, are the reactants in photosynthesis.
Photosynthesis is responsible for absorbing atmospheric carbon dioxide and producing oxygen that is released into the atmosphere. Photosynthesis also creates an enormous biomass of carbohydrate (sugar) energy. Photosynthetic organisms make about 176 billion tons of carbohydrate each year.
History of the Atmosphere
Early in the planet's history, photosynthetic organisms were responsible for oxygenating the atmosphere. According to "Science News," photosynthetic organisms might have begun to oxygenate the atmosphere much earlier than was previously thought, as much as 2.7 billion years ago.