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.
In cellular respiration, cells use oxygen to release energy stored in sugars such as glucose. In fact, most of the energy used by the cells in your body is provided by cellular respiration. Just as photosynthesis occurs in organelles called chloroplasts, cellular respiration takes place in organelles called mitochondria. Remember that mitochondria are in both plant cells and animal cells, so both kinds of cells release energy through cellular respiration.