After this the food is taken down a long tube, called the oesophagus, which takes the food from the mouth to the stomach. The movement of the food is helped by waves of contraction of the muscle surrounding the oesophagus, this is called peristalsis.
Once the food enters the stomach a ring of muscle at the exit called the pyloric sphincter contracts and prevents the food from leaving. For the next two to three hours churning movements of the stomach produce further physical breakdown of food. The only chemical digestion that takes place in the stomach is the breakdown of proteins, which is from the meat in the cheeseburger, to polypeptides. This is done by the enzyme pepsin which comes from the stomach. Hydrochloric acid is also produced by the walls of the stomach, making the pH of the stomach contents very acidic at about 2 pH. This low pH helps the pepsin to digest proteins. The acidity in the stomach also helps to kill any bacteria on the food.
The food then travels through the small intestine, a very long tube of several metres, in which food is moves by peristalsis. It is divided into two parts. In the 1st part, called the duodenum, the process of digestion is completed. The secretions from two other organs are also poured onto food in the duodenum:
The first organ is the pancreas, which produces pancreatic juice. This digestive juice contains protease, lipase and amylase enzymes which digest the protein from the meat of the cheeseburger, fats, which are mainly from the cheese and from the bread, the carbohydrates respectively.
Bile is also poured onto food. This is a viscose, a greeny-brown liquid which is made in the liver and stored in the gall bladder. Bile contains no enzymes but does have two important constituents which help digest iron, which is found in the meat of a cheeseburger. The first are bile salts which emulsify fats, turn them into little droplets. This increases the surface area over which lipase enzymes can act on the fats. The second constituent is sodium hydrogen carbonate. This salt is alkaline and helps to neutralise the strongly acidic contents entering the duodenum from the stomach. The pH in the duodenum needs to be about 7.5 for the enzymes found there to work properly.
This was the last process of digestion in the body and so I will summarize the end products of it. They are:
Glucose, which is the product when maltase acts upon maltose, which came from the bread of the cheeseburger, which contains carbohydrates.
Amino acids, which is the product when protease acts upon polypeptides, which came from the meat of the burger, which contains proteins.
Fatty acids and glycerol, which are the products when lipids, are acted on by lipase, which came from the cheese of the burger, which contains fats.
After all of the cheese burger has been digested there is a final stage in which these end products, glucose, glycerol, fatty acids and amino acids are absorbed into the body. The Ileum, the second part of the small intestine does this.
After the dissolved food molecules have been absorbed by the ileum, the food passes into the colon or large intestine. All that happens here is that water is reabsorbed and then it is stored in the rectum and is past out of the body at will.