Leaves

• Photosynthesis happens in leaves.Hemera Technologies/AbleStock.com/Getty Images
  
  Plants absorb light and carbon dioxide thorough their leaves and water through their roots. The typical leaf consists of a kind of skin called the upper and lower epidermis, a middle part called the mesophyll, vascular bundles that behave like human blood vessels, and stomates -- tiny openings on the lower epidermis that allow the passage of oxygen and carbon dioxide. The mesophyll cells are made up of chloroplasts that contain stroma and chlorophyll-packed thylakoids.
  
  

Sunlight

• Both plants and humans produce ATP in energy metabolism.Ting Hoo/Digital Vision/Getty Images
  
  In the daytime, chlorophyll absorbs sunlight and stores it as ATP (adenosine phosphate). The stroma draw carbon dioxide from the atmosphere. At night, the plant uses the stored light energy to break the water molecules and the carbon dioxide molecules down into their constituent atoms. Through a series of chemical reactions, the atoms recombine to form oxygen and glucose. Plant chemists represent this with the following equation:
  
  6CO2 + 6H2O (+light energy) -------------->C6H12O6 + 6O2
  
  In plain English: Six carbon dioxide molecules and six water molecules combined with light energy recombine to form glucose and oxygen.
  
  

Glucose

• Since plants are able to make their own food in the form of glucose produced in the course of photosynthesis, they are called autotrophs. Plants can store glucose and then use it whenever they need it. This stored, homemade glucose can be called out of storage to produce fat and protein, which is used in turn to rebuild cells, reproduce, bud and flower.
  
  

Oxygen

• Terrastrial life depends on oxygen.Jupiterimages/Photos.com/Getty Images
  
  By taking carbon dioxide out of the atmosphere and putting oxygen into it, photosynthesis makes life on Earth possible. Atmospheric carbon is absorbed by plants and oceans, but according to professors Whitmarsh and Govindjee of the University of Illinois, the amount of carbon in the atmosphere has grown from 280 parts per million 200 years ago to 360 ppm today. If more fossil fuels are burned and more green leafy plants such as trees are destroyed at the expected levels, the amount of carbon in the atmosphere will rise to 700 ppm and may result in higher temperatures on Earth.