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 low density (LDL). The LDL cholesterol is the most harmful form, with which fats are transported into the body and the cells, especially when there is a high concentration of it in the blood, because the cholesterol can accumulate in the vascular walls and cause arteriosclerosis. If other vessel-damaging risk factors add to it, like smoking or high blood pressure, then it increases the risk of secondary diseases like a heart attack, stroke or a peripheral arterial occlusive disease of the legs (PAOD). The reason for all this diseases are sediments in the vessels, that can decrease or completely inhibit the flow of blood. The antagonist of the LDL is the HDL.
