Journey of a Cheese Sandwich 2
Süžeeskeem Tekst
- The pancreas is an elongated organ located behind the stomach and it contains many enzymes (protease, amylase, lipase) to break down food as described earlier and in the box on the left.
- Amylase in the pancreas breaks down the starch in the bread into glucose. Protease breaks down the protein in the cheese into amino acids. Lipase breaks down lipids in the cheese and butter into fatty acids and glycerol.
- The small intestine is a very long (averaging at 7 metres!) tube that loops around and it breaks food down, in the same way as the pancreas. Its function is to further digest food and make it into small, soluble molecules that can be absorbed into the bloodstream, through villi (hair-like structures that increase surface area to increase the diffusion rate). These nutrients in our blood are very useful: proteins are for building and repairing muscle, carbohydrates are broken into glucose and this is used to release energy, and fats and lipids are useful for building cell membranes, storing energy, absorbing vitamins, and producing hormones.
- The same enzymes found in the pancreas perform the same things. Bile that was produced in the liver and stored in the gall bladder neutralises the acid in the sandwich from the stomach so that the enzymes can work effectively in the neutral small intestine. As well as this, the bile breaks lipids down into smaller droplets to increase their surface area to make it easier for the lipase enzyme to work. This is called emulsification.
- The large intestine is a shorter, thicker tube-like structure that goes around the small intestine as shown. Its function is to get rid of any waste products, and absorb water.
- Finally, excess water is absorbed into the body in the large intestine. Any undigested food is passed out from the anus as faeces when we go to the toilet.
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