As you can see from the diagram above, the hydrolysis of ATP to ADP (adenosine diphosphate) and inorganic phosphate (Pi) is exergonic and thus releases energy which cells can use to do any number of things. Once hydrolyzed, ATP can be regenerated from ADP and Pi endergonic and thus requires energy. The energy needed to regenerate ATP is obtained from “food”, whatever that may be.The food we eat is first digested by enzymes as you learned in the previous lab. Once the polymers in your food (e.g., polysaccharides, triglycerides, protein) have been broken down by enzymes into monomers (e.g., monosaccharides such as glucose, fatty acids, amino acids), they enter the blood circulation and are delivered to the cells of the body. Within cells, the processes of fermentation and cellular respiration will further catabolize (break down) these molecules, harvesting the energy they contain for the synthesis of ATP.Let us now take a brief look at fermentation and cellular respiration to see how each process produces ATP using energy released from molecules of glucose. Keep in mind that, although we are focusing on glucose, other molecules such as fatty acids can be used for the same purpose, though in slightly different ways.