Bile (Edexcel IGCSE Biology)
Revision Note
Bile Production & Storage
Bile is an alkaline substance produced by cells in the liver
Before being released into the small intestine, bile is stored in the gall bladder
Bile production and secretion
Examiner Tips and Tricks
Bile contains bile salts. It is these molecules which emulsify the lipids, however you can use both terms interchangeably.
Did this video help you?
The Role of Bile
Bile has two main roles:
Neutralising the hydrochloric acid from the stomach
The alkaline properties of bile allow for this to occur
This neutralisation is essential as enzymes in the small intestine have a higher (more alkaline) optimum pH than those in the stomach
Breaking apart large drops of lipids (fats) into smaller ones (and so increasing their surface area)
This is known as emulsification
The more alkaline conditions and larger surface area allows lipase to chemically break down the lipid molecules into glycerol and fatty acids at a faster rate
Bile salts break large lipid droplets into smaller ones with a larger surface area
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.
You've read 0 of your 5 free revision notes this week
Sign up now. It’s free!
Did this page help you?