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.
The inner membrane parts of mitochondria. Finally there's the matrix, which is the inside of the mitochondria created by the inner membrane. The matrix contains enzymes for cellular respiration as well as its own ribosomes and DNA needed to create some of the proteins important for this process.