Lipid Digestion

• 1. Bile salts produced in the liver act on lipids to split them up into tiny droplets called micelles. This process is called emulsification and increases the surface area of the lipids so pancreatic lipase can catalyse the hydrolysis reaction at a greater rate
• 2. Pancreatic lipase hydrolyse ester bonds joining the fatty acids to the glycerol molecule. These products are packaged into micelles
• 3. Micelles come into contact with the epithelial cells that make up the villi of the ileum
• 4. The micelles break down, releasing the monoglycerides and fatty acids
• 5. Monoglycerides and fatty acids are non-polar so can diffuse across the cell surface membrane
• 6. Fatty acids and monoglycerides are transported to the endoplasmic reticulum where they are recombined to form triglycerides
• 7. Triglycerides move to the golgi apparatus where they associate with cholesterol and lipoproteins to form chylomicrons
• 8. These move out of the epithelial cell by exocytosis and enter the lacteals, which are part of the lymphatic capillaries
• 9. Chylomicrons pass from the lacteal into the bloodstream
• 10. Triglycerides in the chylomicrons are hydrolysed by an enzyme in the endothelial cells that make up the capillaries. The fatty acids then diffuse into cells that make up tissues where they can be used for various metabolic processes