The mitochondria found within the membrane of cells is the organelle that converts sugars into energy. The process, called aerobic cellular respiration, uses sugars and oxygen to create a chemical energy called adenosine triphosphate.
Adeonsine triphosphate, or ATP, is synthesized inside the mitochondria, which is composed of an inner and outer membrane. Both membranes are porous, allowing certain ions and molecules to pass through. However, the inner membrane's pores are smaller, which allows only specific molecules to enter the innermost area. The mitochondrial matrix inside the inner membrane uses the citric acid cycle to produce electrons, which travel through the protein complexes that are accepted inside the membrane. Once oxygen is added, the process creates water molecules, as well the ATP, in the same cycle.