Cambridge O Level Biology · Syllabus 5090 · Human Nutrition
Lipase
What is Lipase?
A digestive enzyme that breaks down lipids into fatty acids and glycerol. It is produced by the pancreas and acts in the small intestine. Its rate of action depends strongly on how much lipid surface is available, which is why bile emulsifies large fat droplets into small ones before lipase works on them.
This definition is part of the Human Nutrition chapter in Cambridge O Level Biology.
Common mistakes with Lipase
- “Bile chemically digests fat.” Why it is wrong Bile changes the size of the droplets, not the molecules. That is physical digestion by definition. Write instead "Bile emulsifies lipid, increasing its surface area so that lipase digests it faster. Lipase does the chemical digestion."
- “Protease digests protein into fatty acids.” Why it is wrong Fatty acids come from lipid, not protein. Protein is built from amino acids, so amino acids are what it breaks down into. Write instead "Protease breaks protein into amino acids. Lipase breaks lipid into fatty acids and glycerol."
Questions students ask about Lipase
Why is bile not an enzyme?
Bile contains no enzymes, catalyses no reaction and breaks no chemical bonds. What it does is emulsify lipids: it breaks large fat droplets into many small ones. Because only the size of the droplets changes and the molecules themselves are unaltered, this is physical digestion. The chemical digestion of lipid is carried out by lipase, which breaks lipid molecules into fatty acids and glycerol.