Cholesterol
Cholesterol refers to a subclass of lipids known as steroids. Cholesterol is also the molecule from which steroid hormones and bile acids are built.
Importance of Cholesterol
Cholesterol is a steroid of fat used to maintain the strength, permeability and flexibility of cell membranes. It also serves as a precursor for the biosynthesis of sex hormones, bile acids, and vitamin D.
Sources of Cholesterol
Cholesterol is predominantly synthesized in our body in Liver and also provided in food. Food also supplements Cholesterol. All foods containing animal fat contain cholesterol to varying extents. Major dietary sources of cholesterol include cheese, egg yolks, beef, pork, poultry, fish, and shrimp. Cholesterol is not found in significant amounts in plant sources. However, ingested cholesterol is esterified. This esterified cholesterol is poorly absorbed. That is the reason that cholesterol intake in food has little effect on total body cholesterol content or concentrations of cholesterol in the blood. In our body, Liver secretes it in a non-esterified form (via bile) into the digestive tract. Typically about 50% of the excreted cholesterol is reabsorbed by the small intestine back into the bloodstream.
Transport of Cholesterol in Lipoproteins
Cholesterol is only slightly soluble in water; it can dissolve and travel in the water-based bloodstream at exceedingly small concentrations. Since cholesterol is insoluble in blood, it is transported in the circulatory system within lipoproteins.
There are several types of lipoproteins in blood, called, in order of increasing density, chylomicrons, very-low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL), low-density lipoprotein (LDL), and high-density lipoprotein (HDL). The more lipid and less protein a lipoprotein has, the less dense it is.
Control of Cholesterol: Statins
Statins are a group of drugs that work to lower cholesterol Levels, particularly the “bad cholesterol”. Low-density lipoprotein known as LDL. The drugs work in two ways. First, they block an enzyme that is needed for cholesterol production. Second, they increase LDL membrane receptors in the liver.
