Bile (Cambridge (CIE) IGCSE Biology)
Revision Note
Written by: Lára Marie McIvor
Reviewed by: Lucy Kirkham
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Bile: Extended
Extended Tier Only
Cells in the liver produce bile which is then stored in the gallbladder
Bile production and secretion
Bile has two main roles:
It is alkaline to neutralise the hydrochloric acid which comes from the stomach
The enzymes in the small intestine have a higher (more alkaline) optimum pH than those in the stomach
It breaks down large drops of fat into smaller ones. This is known as emulsification. The larger surface area allows lipase to chemically break down the lipid into glycerol and fatty acids faster
Examiner Tips and Tricks
Emulsification is the equivalent of tearing a large piece of paper into smaller pieces of paper. This is an example of mechanical digestion, not chemical digestion – breaking something into smaller pieces does not break bonds or change the chemical structure of the molecules which make it up, which is the definition of chemical digestion.
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