Carbon cycle
Carbon enters life forms through the process of photosynthesis. During photosynthesis, carbon dioxide and water combine to produce glucose and oxygen. This changes the atmospheric carbon into glucose molecules.
Glucose, which is a source of food, is utilized by organisms to produce energy during respiration. During this process, glucose is broken down in the presence/absence of oxygen to produce carbon dioxide.
Another process that releases carbon dioxide is combustion or burning. Many substances release carbon dioxide on burning. Vehicular emissions, industrial fumes and the gases released during the process of cooking are some instances of release of carbon dioxide through combustion.
Thus, carbon is cycled repeatedly through different forms by the various physical and biological activities.
