What does bile do?

When we eat a meal, the food passes down a long 'food tube' that runs from the mouth to the anus. Food reaches the stomach by passing along part of this 'food tube' called the oesophagus. Once the food gets to the stomach, it is digested by enzymes. However, the enzymes that work in the stomach work best in acidic conditions. Therefore the stomach produces a very strong acid, known as hydrochloric acid, that provides this acidic environment for the enzymes. The food then moves from the stomach to the next part of the very long 'food tube', which is known as the small intestine. The food is again digested by enzymes in the small intestine, however, these enzymes work best in alkaline conditions. We have to find some way of changing the environment the food is in from acidic to alkaline conditions. This is where bile comes in. Bile is a substance that is made by the liver and is stored in a very small organ called the gall bladder. When food enters the small intestine, bile is secreted (this means released from) the gall bladder to neutralise the acid from the stomach and provide the alkaline conditions needed for the enzymes in the small intestine. Bile also has a second role which is to emulsify fats. Definition of 'to emulsify': this means mixing two liquids together that can't be mixed to form an emulsion. A good example is mixing oil and water. Emulsifying the fats in the food creates a larger surface area for the lipase enzymes to work. This speeds up the digestion process. So overall bile has two roles: to neutralise stomach acid and to emulsify fats.