Bile (Edexcel IGCSE Biology: Double Science)

• 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

• Bile has two main roles:
  1. 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
  2. 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