Emulsification of lipids
Bile salts are produced in the liver and contribute to lipid digestion in the small intestine.
When partially digested food mixes with bile, bile salts disperse large lipid droplets into many smaller droplets. This process is called emulsification.
Emulsification increases the surface area of lipid exposed to the contents of the gut. Lipase molecules therefore have a larger area on which they can act.
Bile entering the duodenum also helps to neutralise the acidic contents arriving from the stomach, so the contents of the duodenum become slightly alkaline.
Bile salts are not digestive enzymes. Emulsification does not hydrolyse the lipid molecules themselves; chemical digestion is carried out by lipase.
Exam Tip: Distinguish the two roles clearly: bile salts emulsify lipids, whereas lipase chemically digests them by hydrolysis. Do not describe bile salts as an enzyme.