What transforms energy in food molecules into usable energy

Cells in our bodies use a process called cellular respiration to break up food molecules such as sugars to into a form that the cells can use as energy. Cellular respiration takes in food and uses it to form ATP.

ATP is a molecule in the cells that stores energy when it is not needed then releases it when it is needed.

The food we eat undergoes digestion where it is broken down to its monomer units e.g. starch is broken down to its glucose units.

Glucose is taken  from the digestive system and into cells where it undergoes glycolysis to produce pyruvate. This takes place in the cytoplasm. 

Pyruvate is then transferred into the mitochondria of the cell where it is then used in the citric acid cycle to produce  ATP. 

oxygen, selenium, tellurium, and polonium.

they're all from the same group as sulfur (group 16).