Cellular respiration might be thought of as a mirror image of photosynthesis. 

The Krebs cycle transfers energy to an electron transport chain in the mitochondria, where a small amount of ATP is made. CO2 is released and several ATP are produced. 

The overall chemical equation for cellular respiration is: 

C₆H₁₂O₆ + 6O₂ --> 6CO₂ + 6H₂O

sugar + oxygen --> carbon dioxide + water

Go through this animation of Cellular Respiration.