Cholesterols are hydroaromatic hydrocarbons. They are produced by the human organism itself and are ingested via animal products. They have various functions. For example: Construction of steroid hormones like estrogen, gestagen, and androgen, but also production of bile acid and building up new tissues. Because fat doesn`t dissolve in blood, the cholesterol is surrounded by an envelope consisting of lipoproteins for its transportation. This is illustrated in the picture. On the inside, in yellow and purple, are the water-insoluble fats like cholesterol, surrounded by the blue-yellow lipoprotein envelope. The apolipoprotein B 100 (red) is attached to the envelope, which is a special protein that increases the solubility of cholesterol in the blood and promotes the intake of cholesterol into the cell by interacting with cell surface receptors. Thus it is an independent risk factor for the fatty degeneration of cells and vessels. The lipoproteins also determine the names of the different forms of transport of cholesterol. They are classified due to their density. The picture shows a lipoprotein with high density (HDL), which is the protective form of cholesterol, which transports fats from the body to the liver in order to metabolize them. The antagonist of HDL is LDL, which is the vessel damaging factor. A quotient consisting of these two parameters serves as an estimation of the risk of arteriosklerosis.
