The major food molecule in living organisms is a sugar called glucose. Most carbohydrates (sugars and starches) are converted into glucose before they are broken down in the cytosol to release energy. ... If oxygen is present, then glucose can be broken all the way down into carbon dioxide and water.
An animal's physiology can indicate it's diet based on what the animal's body can handle processing. For example, animal's with strong bones and teeth can break down food that is tough to eat, this helps obtain energy alot quicker. For instance, giraffes have long and slender necks that are perfect for reaching up to trees. The giraffe's diet would consist of vegetation located in high levels.
