lipoprotein

/lip'euh proh"teen, -tee in, luy'peuh-/, n. Biochem.
any of the class of proteins that contain a lipid combined with a simple protein.
[1905-10; LIPO-1 + PROTEIN]

* * *

Any of a class of organic compounds that contain both lipid (fat) and protein.

They may be soluble (those in egg yolk and blood plasma) or insoluble (those in cell membranes) in water and water solutions. Lipoproteins in blood plasma are the mode of transport for cholesterol, insoluble by itself. Low-density lipoproteins (LDLs) carry cholesterol from the liver, where it is made, to the cells, where it is used; high-density lipoproteins (HDLs) may carry excess cholesterol back to the liver for breakdown and excretion. LDL-bound cholesterol is primarily responsible for deposits in arteries (see arteriosclerosis) that can lead to coronary heart disease, angina pectoris, myocardial infarction, or stroke. HDL does not form such deposits and may actually retard or reduce their buildup.

* * *

      any member of a group of substances containing both lipid (fat) and protein. They occur in both soluble complexes—as in egg yolk and mammalian blood plasma—and insoluble ones, as in cell membranes. The lipoproteins in blood plasma have been intensively studied because they are the mode of transport for cholesterol (q.v.) through the bloodstream and lymphatic fluid.

      Cholesterol is insoluble in the blood, and so it must be bound to lipoproteins in order to be transported. Two types of lipoprotein are involved in this function: low-density lipoproteins (LDLs) and high-density lipoproteins (HDLs). LDLs transport cholesterol from its site of synthesis in the liver to the body's cells, where the cholesterol is separated from the LDL and is then used by the cells for various purposes. HDLs probably transport excess or unused cholesterol from the body's tissues back to the liver, where the cholesterol is broken down to bile acids and is then excreted. About 70 percent of all cholesterol in the blood is carried by LDL particles, and most of the remainder is carried by HDLs. LDL-bound cholesterol is primarily responsible for the atherosclerotic buildup of fatty deposits on the blood vessel walls, while HDL particles may actually reduce or retard such atherosclerotic buildups and are thus beneficial to health.

      Body cells extract cholesterol from the blood by means of tiny coated pits (receptors) on their surfaces; these receptors bind with the LDL particles (and their attached cholesterol) and draw them from the blood into the cell. There are limits to how much cholesterol a body cell can take in, however, and a cell's capture of LDL particles inhibits the making of more LDL receptors on that cell's surface, thus lowering its future intake of cholesterol. Fewer receptors on the body cells means that less cholesterol is ingested by the cells and that more remains in the bloodstream, thus increasing the risk of cholesterol accumulating in the interior walls of blood vessels.

      Several hereditary genetic disorders, called hyperlipoproteinemias, involve excessive concentrations of lipoproteins in the blood. Other such diseases, called hypolipoproteinemias, involve abnormally reduced lipoprotein levels in the blood.

* * *


Universalium. 2010.

Look at other dictionaries:

  • Lipoprotein(a) — (also called Lp(a)) is a lipoprotein subclass. Studies have identified Lp(a) as a putative risk factor for atherosclerotic diseases such as coronary heart disease and stroke.cite journal | author = Danesh J, Collins R, Peto R | title =… …   Wikipedia

  • Lipoprotein-X — (Lp X) is an abnormal low density lipoprotein found in cholestasis. Structure Lipoprotein X is a lamellar particle of 30 to 70 nm in diameter as revealed by electron microscopy. It is characterized by its high content of phospholipids (66% by… …   Wikipedia

  • lipoprotein — [lip΄əprō′tēn΄, lip΄əprō′tē in] n. any of a group of proteins combined with a lipid, found as in blood plasma or egg yolk …   English World dictionary

  • Lipoprotein a — Apolipoprotein(a) Masse/Länge Primärstruktur 4529 Aminosäuren …   Deutsch Wikipedia

  • Lipoprotein — [ thumb|250px|Lipoprotein structure (chylomicron) ApoA, ApoB, ApoC, ApoE (apolipoproteins); T (triacylglycerol); C (cholesterol); green (phospholipids)] A lipoprotein is a biochemical assembly that contains both proteins and lipids. The lipids or …   Wikipedia

  • Lipoprotein — Lipoproteine sind nicht kovalente Aggregate aus Lipid und Protein und bilden mizellenähnliche Partikel mit einem unpolaren Kern aus Cholesterinestern und Triglyceriden und einer zur wässrigen Phase gerichteten Hülle mit polaren, hydrophilen… …   Deutsch Wikipedia

  • Lipoprotein — A complex of lipid and protein, the way lipids travel in the blood. Cholesterol, a building block of the outer layer of cells (cell membranes), is transported through the blood in the form of water soluble carrier molecules known as lipoproteins …   Medical dictionary

  • lipoprotein — n. one of a group of compounds, found in blood plasma and lymph, each consisting of a protein (see apolipoprotein) combined with a lipid (which may be cholesterol, a triglyceride, or a phospholipid). Lipoproteins are important for the transport… …   The new mediacal dictionary

  • Lipoprotein — lipoproteinai statusas T sritis ekologija ir aplinkotyra apibrėžtis Sudėtiniai baltymai, kurių molekulės susideda iš baltyminės dalies ir lipidų. Yra kraujyje, ląstelių ir organoidų membranose. atitikmenys: angl. lipoprotein vok. Lipoprotein, n… …   Ekologijos terminų aiškinamasis žodynas

  • lipoprotein(a) — /lip euh proh teen a , tee in ay , luy peuh /, n. a plasma lipoprotein containing protein and cholesterol, high levels of which are associated with atherosclerosis. * * * …   Universalium

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.