Secretion is the process of, elaborating and releasing chemicals from a cell, or a secreted chemical substance or amount of substance. In contrast to excretion, the substance may have a certain function, rather than being a waste product.
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Secretin Life Line
"The Secretions are men of peace in a world of mayhem. ... to get a few former Secretions such as Dave Leon and ... Secretions are reviewed in The Examiner ...secretinlifeline.blogspot.com/Microbiology Blog: The weblog for microbiologists
The Type V secretion system was first described twenty years ago. ... This secretion mechanism has been subdivided into sub-types (a), (b) and (c), as ...www.horizonpress.com/blogger/labels/protein%20secretion.htmlsecretion " Blog Archive " First impressions of the site
Check the site out for his Blog, book information, upcoming events and the ability to email... seem to delete comments from my own blog and can't comment ...tomgreen.com/blogs/secretion/2009/04/04/first-impressions-of...Bacterial Secretion Systems - Type II
Microbiology Blog: The weblog for microbiologists: Microbiology news and views ... Labels: bacteria, protein, protein secretion, proteins, Pseudomonas, toxin ...www.horizonpress.com/blogger/2008/11/bacterial-secretion-sys...Paranormal Research and Investigative Studies Midwest (P.R.I.S.M.)
Privately funded paranormal research organization provides investigative support for any haunting experience. Site provides various paranormal investigative reports and images.www.doyouseedeadpeople.org/Secretion is the process of, elaborating and releasing chemicals from a cell, or a secreted chemical substance or amount of substance. In contrast to excretion, the substance may have a certain function, rather than being a waste product.
Secretion in bacterial species means the transport or translocation of effector molecules for example proteins, enzymes or toxins (such as cholera toxin in pathogenic bacteria for example Vibrio cholerae) from across the interior (cytoplasm or cytosol) of a bacterial cell to its exterior. Secretion is a very important mechanism in bacterial functioning and operation in their natural surrounding environment for adaptation and survival.
Mechanism
Eukaryotic cells, including human cells, have a highly evolved process of secretion. Proteins targeted for the outside are synthesized by ribosomes docked to the rough endoplasmic reticulum. As they are synthesized, these proteins translocate into the ER lumen, where they are glycosylated and where molecular chaperones aid protein folding. Misfolded proteins are usually identified here and retrotranslocated by ER-associated degradation to the cytosol, where they are degraded by a proteasome. The vesicles containing the properly-folded proteins then enter the Golgi apparatus.
In the Golgi apparatus, the glycosylation of the proteins is modified and further posttranslational modifications, including cleavage and functionalization, may occur. The proteins are then moved into secretory vesicles which travel along the cytoskeleton to the edge of the cell. More modification can occur in the secretory vesicles (for example insulin is cleaved from proinsulin in the secretory vesicles).
Eventually, the vesicle fuses with the cell membrane at a structure called the porosome, in a process called exocytosis, dumping its contents out of the cell's environment.
Strict biochemical control is maintained over this sequence by usage of a pH gradient: the pH of the cytosol is 7.4, the ER's pH is 7.0, and the cis-golgi has a pH of 6.5. Secretory vesicles have pHs ranging between 5.0 and 6.0; some secretory vesicles evolve into lysosomes, which have a pH of 4.8.
Nonclassical secretion
There are many proteins like FGF1 (aFGF), FGF2 (bFGF), interleukin1 (IL1) etc which do not have a signal sequence. They do not use the classical ER-golgi pathway. These are secreted through various nonclassical pathways.
Secretion in human tissues
Many human cell types have the ability to be secretory cells. They have a well developed endoplasmic reticulum and Golgi apparatus to fulfill their function. Tissues in humans that produce secretions include the gastrointestinal tract which secretes digestive enzymes and gastric acid, and the lung which secretes surfactants.
Secretion in Gram negative bacteria
Secretion is not unique to eukaryotes alone, it is present in bacteria and archaea as well. ATP binding cassette (ABC) type transporters are common to all the three domains of life. The Sec system is also another conserved secretion system which is homologous to the translocon in the eukaryotic endoplasmic reticulum consisting of Sec 61 translocon complex in yeast and Sec Y-E-G complex in bacteria. Secretion via the Sec pathway generally requires the presence of an N-terminal signal peptide on the secreted protein. Gram negative bacteria have two membranes, thus making secretion topologically more complex. There are at least six specialized secretion systems in Gram negative bacteria.























