In photosynthesis, a green plant uses energy from sunlight to turn carbon   dioxide and water into glucose, a simple sugar. Oxygen is released as a   by-product. 

 The water is absorbed by the plant through its roots. It gets carbon dioxide 
 from the air: it diffuses into the leaf through tiny air holes. Sunlight is 
 absorbed by the pigment chlorophyll, which passes on the energy to 
 proteins in the chloroplast, so that there is enough energy to drive the   manufacture of glucose.