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Organisms need energy to survive. Some organisms are capable of absorbing energy from sunlight and using it to produce sugar and other organic compounds such as lipids and proteins. The sugars are then used to provide energy for the organism. This process, called photosynthesis, is used by plants and some protists, bacteria, and blue-green algae.
In photosynthesis, solar energy is converted to chemical energy. The chemical energy is stored in the form of glucose (sugar). Carbon dioxide, water, and sunlight are used to produce glucose, oxygen, and water. The chemical equation for this process is:
6CO2 + 12H2O + light → C6H12O6 + 6O2 + 6H2O
6 molecules of carbon dioxide (6CO2) and 12 molecules of water (12H2O) are consumed in the process, while glucose (C6H12O6), six molecules of oxygen (6O2), and six molecules of water (6H2O) are produced.
This equation may be simplified as: 6CO2 + 6H2O + light → C6H12O6 + 6O2.
Photosynthesis in Plants
In plants, photosynthesis occurs mainly within the leaves. Since photosynthesis requires carbon dioxide, water, and sunlight, all of these substances must be obtained by or transported to the leaves. Carbon dioxide is obtained through tiny pores in plant leaves called stomata. Oxygen is also released through the stomata. Water is obtained by the plant through the roots and delivered to the leaves through vascular plant tissue systems. Sunlight is absorbed by chlorophyll, a green pigment located in plant cell structures called chloroplasts. Chloroplasts are the sites of photosynthesis.