There are several types of lipids; only triglycerides (fats) are considered here. Reaction arrows are shown in green.
Triglycerides consist of three fatty acids and one glycerol molecule. The enzyme lipase removes two of the fatty acids leaving one attached to the glycerol forming a monoglyceride.
Triglycerides--and other lipids--are not water soluble and remain clustered together. The enzyme pancreatic lipase is water soluble and can only hydrolyze triglycerides that are at the surface of the lipid clusters. Bile increases the total surface area of the lipid clusters by forming many small clusters that do not regroup--emulsified fat.
Small droplets of fatty acids and monoglycerides that are called micelles diffuse into the cells lining the small intestine. Within these cells they are recombined into triglycerides (not shown here) and packaged as water-insoluble packets called chylomicrons that leave the cell by exocytosis to enter the lymphatic lacteals.
Last Updated: 7/19/2005