1. Describe how different parts of the human digestive system help to break down molecules of fat so that they can be absorbed into the body.

Fat is first processed by mechanical breakdown in the mouth through chewing and in the stomach through its ‘churning’ action. Lipase, an enzyme produced in the pancreas, converts fat in the small intestine into fatty acids and glycerol. Chewing helps to increase the surface area of food and hence increase the rate of this breakdown. Bile acids, which are produced by the liver, aid this process by emulsifying the fat (further increasing surface area) and by packaging the fatty acids and glycerol into small, water-soluble molecules which can be absorbed by the small intestine. Bile also helps to neutralise acid from the stomach, reducing acid reflux and producing alkaline conditions in the small intestine where the fat is being broken down and aborbed.