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.
It's not like the movies at all. Mitochondria are special because they have their own ribosomes and DNA floating in the matrix. There are also structures called granules which may control concentrations of ions. Cell biologists are still exploring the activity of granules. Using Oxygen to Release Energy How does cellular respiration occur in mitochondria?