The human body is a fascinating machine. Even something as simple as digesting your food takes the work of hundreds of chemicals and processes, which you have no idea are occurring. Your body uses an arsenal of enzymes to break down carbohydrates, fats and proteins. This is the only way you can make food chemically small enough to get the nutrients into your bloodstream and ultimately into your cells. If it were not for these enzymes, you could eat as much as you wanted, but still starve because you would not digest your food.
The journey of food in the process of digestion begins in the mouth. Salivary amylase is the first enzyme your food encounters. It is secreted by the salivary glands, and it begins the process of breaking down complex sugars and starches. Protein and fat pass through the mouth and the food pipe, or esophagus, chemically whole.
In the stomach, enzymes act on your food to break it down further for use by your body. The enzyme pepsin starts to break protein apart into shorter pieces called peptides. Hydrochloric acid also acts on the mass of food, but because of the acidity, no further carbohydrate digestion takes place. Both alcohol and aspirin are directly absorbed through the stomach's walls, however.
As the food comes from the stomach, it enters the first part of the small intestine, or duodenum. This is where the pancreas secretes its enzymes into the food bolus to break it down even further. Pancreatic amalyase takes all the starch and breaks it down into maltose. The pancreas also secretes trypsin and chemotrypsin to break down proteins into peptides. Lipase is secreted to change fats into fatty acids and glycerol. Bile from the liver and gallbladder also work on fat to emulsify it or break it into smaller pieces.
The food moves further into the small intestine where the bulk of the digestion takes place. It is also where the absorption of the food occurs. Cells in the small intestine release peptidases to break down peptides into amino acids, which are then absorbed into the bloodstream. Maltases are also released to change maltose into monosaccharides for absorption into the bloodstream.