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Cholesterol is a steroid lipid, found in the cell membranes of all body tissues, and transported in the blood plasma, of all animals. Most cholesterol is produced internally, not dietary in origin. It is present in higher concentrations in tissues which either produce more or have more densely packed membranes; for example the liver, spinal cord, brain and atheroma. Cholesterol plays a central role in many biochemical processes, but is best known for the association of cardiovascular disease with various lipoprotein cholesterol transport patterns in the blood.1 History of the name
The name originates from the Greek chole- ( bile) and stereos (solid), as researchers first identified cholesterol in solid form in gallstoneIn medicine, gallstones are crystalline bodies formed within the body by accretion or concretion of normal or abnormal bile components. Cholesterol stones are usually white or yellow in color and account for about 80 percent of gallstones. They are made ps.
2 Physiology
2.1 Synthesis
Cholesterol is primarily synthesized from acetyl CoA through the HMG-CoA reductase pathwayThe HMG-CoA reductase pathway is an important cellular metabolic pathway present in virtually all organisms. It forms hydrophobic molecules for tasks as diverse as cell membrane maintenance, hormones, protein anchoring and N glycosylation. Reactions Acety in many cellA cell is a single unit or compartment, enclosed by a border or wall. Examples of cells: prison cell monastic cell cell in biology electrochemical cell radio cell, as used in cellular mobile and cell phone table cell, as used in HTML / web pages Geometrics/ tissuesBiological tissue is a group of cells that perform a similar function. The study of tissues is known as histology, or, in connection with disease, histopathology. The classical tools for studying the tissues are the wax block, the tissue stain, and the op. About 20–25% of total daily production (~1 gFor other meanings of gram see gram (disambiguation). The gram (also spelt gramme is a unit of measurement of mass, and is defined in the SI system of units as one thousandth of a kilogram. See 1 E -3 kg for comparisons with other masses. The symbol for g/ dayA day is any of several different units of time. The word refers either to the period of light when the Sun is above the local horizon or to the full day covering a dark and a light period. Introduction Different definitions of the day are based on the ap) occurs in the liver, other sites of higher synthesis rates include the intestines, adrenal glands and reproductive organs.
2.2 Properties
Cholesterol is minimally soluble in water; it cannot dissolve and travel in the water-based blood stream. Instead, it is transported in the blood stream by lipoproteins; protein "molecular-suitcases" which are water soluble and carry cholesterol and fats internally. The proteins forming the surface of the given lipoprotein particle determine from what cells cholesterol will be removed and to where it will be supplied.
The largest lipoproteins, which primarily transport fats from the intestinal mucosa to the liver are called chylomicrons. They carry mostly triglyceride fats and cholesterol (both from food and especially internal cholesterol secreted by the liver into the bile). In the liver, chylomicron particles give up triglycerides and some cholesterol and are converted into low-density lipoprotein (LDL) particles which carry triglycerides and cholesterol on to other body cells. In healthy individuals the low-density lipoprotein (LDL) particles are large and relatively few in number. Conversely, large numbers of small low-density lipoprotein (LDL) particles are strongly associated with promoting atheromatous disease within the arteries. (Lack of information on low-density lipoprotein (LDL) particle number and size is one of the major problems of conventional lipid tests.)
High-density lipoprotein ( HDL) particles transport cholesterol back to the liver for excretion, but vary considerably in their effectiveness for doing this. Having large numbers of large HDL particles correlates with better health outcomes. Conversely, having small amounts of large HDL particles is strongly associated with atheromatous disease progression within the arteries. (Note that the concentration of total HDL does not indicate the actual number of functional large HDL particles, one of the major problems of conventional lipid tests.)
The cholesterol in LDL cholesterol and the cholesterol in HDL cholesterol are identical. The only difference between the two is the carrier protein molecules (i.e. the lipoprotein).
