Sandbox Reserved 166
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Revision as of 03:45, 30 March 2011
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| This Sandbox is Reserved from March 9, 2011, through May 30, 2011 for use by the course Biochemistry at Reinhardt University, Waleska, USA, taught by Irma Santoro. This reservation includes Sandbox Reserved 162 through Sandbox Reserved 168. |
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Background
Albumin in general refers to any protein that is water soluble. Albumins are commonly found in blood plasma as a serum transport protein. Other serum transport proteins are: alpha-fetoprotein, vitamin D-binding protein, and afamin.[1].
Where and how it is synthesized
SA is produced in the liver. Albumin synthesis begins in the nucleus, where genes are transcribed into messenger ribonucleic acid (mRNA). The mRNA is secreted into the cytoplasm, where it is bound to ribosomes, forming polysomes that synthesize preproalbumin. Preproalbumin is an albumin molecule with a 24 amino acid extension at the N terminal peptide. The extension releases the preproalbumin into the rough endoplasmic reticulum. Once inside the endoplasmic reticulum, the leading 18 amino acids of this extension are cleaved, leaving proalbumin (albumin with the remaining extension of 6 amino acids). Proalbumin is the principal intracellular form of albumin. Proalbumin is exported to the Golgi apparatus, where the extension of 6 amino acids is removed before the albumin is secreted by the liver cells. Once synthesized, albumin is secreted immediately; it is not stored in the liver. The serum albmin is distributed to the tissues of the body, a majority of it is distributed in the skin. Albumin is distributed within the vascular compartments of the muscle, skin, liver, gut, and other tissues.[2].
Function
Serum albumin (SA) is the main protein in blood plasma, it accounts for about 50 percent of the protein in the blood plasma. SA binds to water, cations ( such as Ca2+, Na+, and K+), fatty acids, hormones, bilirubin, and drugs. It transports thyroid hormones, and other hormones that are fat-soluble. It also transports “free” fatty acids to the liver and unconjugated bilirubin. It is also a carrier for two materials necessary for the control of blood clotting: antithrombin, which keeps the clotting enzyme thrombin from working unless it is needed, and heparin cofactor, which is needed for heparin to anticlot. Its main function is to regulate the colloidal osmotic pressure of blood. When plasma proteins, especially albumin, no longer sustain sufficient colloid osmotic pressure to counterbalance hydrostatic pressure, edema develops. Albumin helps in keeping the fluid from the blood from leaking out into the tissues. It serves as a carrier of molecules of low water solubility by isolating their hydrophobic nature in albumins binding sites. [3].
References
1. Vincent JL. Relevance of albumin in modern critical care medicine. Best Pract Res Clin Anaesthesiol. Jun 2009;23(2):183-91 2. Rothschild MA, Oratz M, Schreiber SS. Albumin synthesis. 1. N Engl J Med. Apr 6 1972;286(14):748-57. [Medline]. 3. Peralta,Ruben. Hypoalbuminemia.webMD.Apr 15 2010
