The Latin verb supponere, meaning substitute, has several legitimate heirs in English, including supposititious (which dates from the early 17th century) and supposition (a 15th century addition).
Cellular respiration takes place in the organelles called mitochondria. The mitochondria take in glucose, a type of sugar, and change it in the presence of oxygen into an energy-rich molecule called ATP, or adenosine triphosphate. For every molecule of glucose, 36 molecules of ATP are made.
Both reactions are accomplished in organelles; chloroplasts are the sites of photosynthesis, and cellular respiration happens mainly in the mitochondria. Only photosynthetic organisms can make glucose, but all organisms must be able to use that energy. This energy usually comes in the form of ATP, or adenosine triphosphate. Cellular respiration produces ATP. The glucose is burned to produce the ATP. Cellular respiration consists of four steps.