A lipoprotein is a biochemical assembly that contains both proteins and lipids. (more properly known as, TAG or triacylglyceride) is Glyceride in which the Glycerol is Esterified with three Fatty acids It is the Cholesterol is a Lipid found in the Cell membranes and transported in the Blood plasma of all Animals It is an essential component of mammalian Phospholipids are a class of Lipids and are a major component of all Biological membranes All phospholipids contain a Diglyceride, a Phosphate Biochemistry is the study of the chemical processes in living Organisms It deals with the Structure and function of cellular components such as Proteins are large Organic compounds made of Amino acids arranged in a linear chain and joined together by Peptide bonds between the Carboxyl Lipids are broadly defined as any fat- Soluble ( lipophilic) naturally-occurring Molecule, such as fats oils waxes cholesterol sterols fat-soluble The lipids or their derivatives may be covalently or non-covalently bound to the proteins. Many enzymes, transporters, structural proteins, antigens, adhesins and toxins are lipoproteins. Enzymes are Biomolecules that catalyze ( ie increase the rates of Chemical reactions Almost all enzymes are Proteins An antigen (from antibody-generating) or immunogen is a substance that prompts the generation of Antibodies and can cause an immune response Adherence is often an essential step in bacterial Pathogenesis or Infection, required for Colonizing a new host. A toxin ( Greek:, toxikon, lit (poison for use on arrows is a Poisonous substance produced by living cells or organisms that is active at very low Examples include the high density and low density lipoproteins of the blood, the transmembrane proteins of the mitochondrion and the chloroplast, and bacterial lipoproteins [1]. High-density lipoproteins ( HDL) is one of the 5 major groups of Lipoproteins ( Chylomicrons, VLDL, IDL, LDL, HDL Low-density lipoprotein ( LDL) is a type of Lipoprotein that transports Cholesterol and Triglycerides from the Liver to peripheral Blood is a specialized Bodily fluid that delivers necessary substances to the body's cells €”such as nutrients and oxygen—and transports Waste products Cytochromes are in general membrane-bound Hemoproteins that contain Heme groups and carry out Electron transport. In Cell biology, a mitochondrion (plural mitochondria) is a membrane-enclosed Organelle found in most eukaryotic cells. Chloroplasts are Organelles found in Plant cells and eukaryotic Algae that conduct Photosynthesis.

Contents 1 Function 2 Classification 2.1 By density 2.2 Alpha and beta 2.3 Lipoprotein(a) 3 Metabolism 3.1 Exogenous pathway 3.2 Endogenous pathway 4 See also 5 External links

Function

The lipids are often an essential part of the complex, even if they seem to have no catalytic activity themselves. To isolate transmembrane lipoproteins from their associated membranes, detergents are often needed. MembraneA biological membrane or biomembrane is an enclosing or separating Amphipathic layer that acts as a barrier within or around a cell. A detergent (as a noun is a material intended to assist Cleaning.

All cells use and rely on fats and, for all animal cells, cholesterol as building blocks to create the multiple membranes which cells use to both control internal water content, internal water soluble elements and to organize their internal structure and protein enzymatic systems. The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called Fats consist of a wide group of compounds that are generally soluble in organic solvents and largely insoluble in water Cholesterol is a Lipid found in the Cell membranes and transported in the Blood plasma of all Animals It is an essential component of mammalian The cell membrane (also called the plasma membrane, plasmalemma, or "phospholipid bilayer" is a Selectively permeable Lipid bilayer

Lipoproteins in the blood, an aqueous medium, carry fats around the body. The protein particles have hydrophilic groups aimed outward so as to attract water molecules; this makes them soluble in the salt water based blood pool. Hydrophile, from the Greek (hydros "water" and φιλια (philia "friendship" refers to a physical property of a Molecule Triglyceride-fats and cholesterol are carried internally, shielded from the water by the protein particle.

The interaction of the proteins forming the surface of the particles with (a) enzymes in the blood, (b) with each other and (c) with specific proteins on the surfaces of cells determine whether triglycerides and cholesterol will be added to or removed from the lipoprotein transport particles.

Regarding atheroma development and progression vs. In Pathology, an atheroma (plural atheromata is an accumulation and swelling (-oma in Artery walls that is made up of cells (mostly Macrophage cells regression, the key issue has always been cholesterol transport patterns, not cholesterol concentration itself.

Classification

By density

General categories of lipoproteins, listed in order from larger and less dense (more fat than protein) to smaller and more dense (more protein, less fat):

• Chylomicrons - carry triacylglycerol (fat) from the intestines to the liver, skeletal muscle, and to adipose tissue. Chylomicrons are large lipoprotein particles that transport dietary lipids from the intestines to other locations in the body (more properly known as, TAG or triacylglyceride) is Glyceride in which the Glycerol is Esterified with three Fatty acids It is the In Anatomy, the intestine is the segment of the alimentary canal extending from the Stomach to the Anus and in humans and other mammals consists The liver is a vital organ in the human body and is present in Vertebrates and some other animals Skeletal muscle is a type of Striated muscle, which usually attaches to tendons "Adipose" redirects here For the Doctor Who monster see " Partners in Crime "
• Very low density lipoproteins (VLDL) - carry (newly synthesised) triacylglycerol from the liver to adipose tissue. (more properly known as, TAG or triacylglyceride) is Glyceride in which the Glycerol is Esterified with three Fatty acids It is the
• Intermediate density lipoproteins (IDL) - are intermediate between VLDL and LDL. They are not usually detectable in the blood.
• Low density lipoproteins (LDL) - carry cholesterol from the liver to cells of the body. Low-density lipoprotein ( LDL) is a type of Lipoprotein that transports Cholesterol and Triglycerides from the Liver to peripheral Sometimes referred to as the "bad cholesterol" lipoprotein.
• High density lipoproteins (HDL) - collects cholesterol from the body's tissues, and brings it back to the liver. High-density lipoproteins ( HDL) is one of the 5 major groups of Lipoproteins ( Chylomicrons, VLDL, IDL, LDL, HDL Sometimes referred to as the "good cholesterol" lipoprotein.

Alpha and beta

It is also possible to classify lipoproteins as "alpha" and "beta", akin to the classification of proteins in serum protein electrophoresis. Serum protein electrophoresis (SPEP is a laboratory test that examines specific proteins in the Blood called Globulins. This terminolgy is sometimes used in describing lipid disorders such as Abetalipoproteinemia. Abetalipoproteinemia, or Bassen-Kornzweig syndrome, is a rare Autosomal recessive disorder that interferes with the normal absorption of fat and fat-soluble vitamins

Lipoprotein(a)

Lipoprotein(a) - Lp(a), Cardiology diagnostic tests

Normal: <14mg/dL

High risk: >19mg/dL

How to lower: aerobic exercise, niacin, aspirin, guggulipid. Aerobic exercise refers to Exercise that involves or improves oxygen consumption by the body Niacin, also known as vitamin B3, is a water-soluble vitamin which prevents the deficiency disease Pellagra. Aspirin, or acetylsalicylic acid (ASA (əˌsɛtɨlsælɨˌsɪlɨk ˈæsɨd is a Salicylate drug, often used as an Analgesic to relieve Commiphora wightii ( Guggal, Guggul or Mukul myrrh tree) is a Flowering plant in the family Burseraceae.

source: Beyond Cholesterol, Julius Torelli MD, 2005 ISBN 0-312-34863-0 p. 91

Metabolism

The handling of lipoproteins in the body is referred to as lipoprotein metabolism. It is divided into two pathways, exogenous and endogenous, depending in large part on whether the lipoproteins in question are composed chiefly of dietary (exogenous) lipids or whether they originated in the liver (endogenous).

Exogenous pathway

Epithelial cells lining the small intestine readily absorb lipids from the diet. In biology and medicine epithelium is a tissue composed of cells that line the cavities and surfaces of structures throughout the body In Biology the small Intestine is the part of the Gastrointestinal tract (gut between the Stomach and the Large intestine, and comprises These lipids, including triglycerides, phospholipids, and cholesterol, are assembled with apolipoprotein B-48 into chylomicrons. Chylomicrons are large lipoprotein particles that transport dietary lipids from the intestines to other locations in the body These nascent chylomicrons are secreted from the intestinal epithelial cells into the lymphatic circulation in a process that depends heavily on apolipoprotein B-48. The lymphatic system in Vertebrates is a network of conduits that carry a clear fluid called Lymph. As they circulate through the lymphatic vessels, nascent chylomicrons bypass the liver circulation and are drained elsewhere into the bloodstream.

In the bloodstream, HDL particles donate apolipoprotein C-II and apolipoprotein E to the nascent chylomicron; the chylomicron is now considered mature. Via apolipoprotein C-II, mature chylomicrons activate lipoprotein lipase (LPL), an enzyme on endothelial cells lining the blood vessels. Lipoprotein lipase ( is an Enzyme that Hydrolyzes Lipids in Lipoproteins like those found in Chylomicrons and very low-density The endothelium is the thin layer of cells that line the interior surface of Blood vessels forming an interface between circulating Blood in the LPL catalyzes a hydrolysis reaction that ultimately releases glycerol and fatty acids from the chylomicrons. Hydrolysis is a Chemical reaction during which one or more water molecules are split into hydrogen and hydroxide ions which may go on to participate in further reactions In Chemistry, especially Biochemistry, a fatty acid is a Carboxylic acid often with a long unbranched Aliphatic tail ( chain) which Glycerol and fatty acids can be absorbed in peripheral tissues, especially adipose and muscle, for energy and storage. "Adipose" redirects here For the Doctor Who monster see " Partners in Crime " Muscle (from Latin musculus, diminutive of mus "mouse" is contractile tissue of the body and is derived from the

The hydrolyzed chylomicrons are now considered chylomicron remnants. The chylomicron remnants continue circulating until they interact via apolipoprotein E with chylomicron remnant receptors, found chiefly in the liver. This interaction causes the endocytosis of the chylomicron remnants, which are subsequently hydrolyzed within lysosomes. Endocytosis is a process where cells absorb material ( Molecules such as proteins from the outside by engulfing it with their Cell membrane. Lysosomes are Organelles that contain Digestive enzymes (acid Hydrolases. Lysosomal hydrolysis releases glycerol and fatty acids into the cell, which can be used for energy or stored for later use.

Endogenous pathway

The liver is another important source of lipoproteins, principally VLDL. Triacylglycerol and cholesterol are assembled with apolipoprotein B-100 to form VLDL particles. Nascent VLDL particles are released into the bloodstream via a process that depends upon apolipoprotein B-100.

As in chylomicron metabolism, the apolipoprotein C-II and apolipoprotein E of VLDL particles are acquired from HDL particles. Once loaded with apolipoproteins C-II and E, the nascent VLDL particle is considered mature.

Again like chylomicrons, VLDL particles circulate and encounter LPL expressed on endothelial cells. Apolipoprotein C-II activates LPL, causing hydrolysis of the VLDL particle and the release of glycerol and fatty acids. These products can be absorbed from the blood by preipheral tissues, principally adipose and muscle. The hydrolyzed VLDL particles are now called VLDL remnants or intermediate density lipoproteins (IDLs). VLDL remnants can circulate and, via an interaction between apolipoprotein E and the remnant receptor, be absorbed by the liver, or they can be further hydrolyzed by hepatic lipase. Hepatic lipase is a form of Lipase. It is expressed in the Liver and Adrenal glands

Hydrolysis by hepatic lipase releases glycerol and fatty acids, leaving behind IDL remnants, called low density lipoproteins (LDL), which contain a relatively high cholesterol content. Low-density lipoprotein ( LDL) is a type of Lipoprotein that transports Cholesterol and Triglycerides from the Liver to peripheral LDL circulates and is absorbed by the liver and peripheral cells. Binding of LDL to its target tissue occurs through an interaction between the LDL receptor and apolipoprotein B-100 or E on the LDL molecule. The LDL Receptor is a mosaic protein that mediates the Endocytosis of cholesterol-rich LDL. Absorption occurs through endocytosis, and the internalized LDL particles are hydrolyzed within lysosomes, releasing lipids, chiefly cholesterol. Endocytosis is a process where cells absorb material ( Molecules such as proteins from the outside by engulfing it with their Cell membrane.

See also

• Apolipoprotein
• Lipid anchored protein
• Lipid anchor

External links

• Database of bacterial lipoproteins at mrc-lmb.cam.ac.uk
• Overview and diagram at washington.edu
• Lipoprotein assembly at wisc.edu
• Lipoprotein circulation at purdue.edu
• MeSH Lipoproteins
• MeSH Proteolipids

In lipid anchored proteins, a covalently attached Fatty acid such as Palmitate or Myristate serves to anchor them to either face of the Cell membrane In lipid anchored proteins, a covalently attached Fatty acid such as Palmitate or Myristate serves to anchor them to either face of the Cell membrane Medical Subject Headings ( MeSH) is a huge Controlled vocabulary (or metadata system for the purpose of indexing journal articles and books Medical Subject Headings ( MeSH) is a huge Controlled vocabulary (or metadata system for the purpose of indexing journal articles and books

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