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.
Cellular respiration is the process of using oxygen in the mitochondria to chemically break down organic molecules such as glucose to release the energy stored in its bonds. In the process molecules of water and carbon dioxide are released as waste products.