posted by Nancy .
"The body absorbs lipids mostly within the small intestine. The gallbladder secrets a chemical called bile to aid in the breakdown of this fat. From there the fat is broken down farther by the enzymes the pancreas makes. The mixture of "fatty acids, partially digested triglycerides and bile form micelles" (Grosvenor & Smolin, 2006, p.128) this stimulates the absorption process. After the absorption the triglycerides are reassembled and the majority of the bile is returned to the liver ready to repeat the process."
Triglycerides cannot pass through cell membranes freely. Special enzymes on the walls of blood vessels called lipoprotein lipases must break down triglycerides into free fatty acids and glycerol. Lipoproteins can be classified as High-density lipoproteins (HDL's) and Low-density lipoproteins (LDL's). LDL's are associated with artery and heart disease and are often referred to as "bad cholesterol". What determines the classification into these categories?
IT is density. However, the classifications are important, because the majority of the HDL is returned to the liver, and the LDL is not.
See Blood Transport in this article
1) type of fatty acid.
2) ratio of lipid:protein
3) amount of TG and cholesterol.