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Cells Communicating with their Environment

Cells need to communicate with their environment so they can respond appropriately (Overview, 2005). The external signal to the cell may come from one of four major pathways: hydrophobic molecules, ion channels, G-protein-coupled receptors, or enzymes. The signal often continues to propagate through the cell and may reach the nuclear DNA to induce the expression of proteins. Hydrophilic molecules can move in and out of cells by passing through the lipid bilayer. Nitric oxide (NO), arachidonic acid and steroids play important roles in cell signaling. With NO and arachidonic acid, cascades do not occur within the same cell, but newly generated nitric oxide and arachidonic acid diffuse to react with target molecules on neighboring cells.

NO may stimulate soluble guanylyl cyclase to produce cGMP which is used to regulate several enzymes and ion channels, and relaxes smooth muscle (Overview, 2005). Normally, cGMP is soon converted to GMP by phosphodiesterase. Arachidonic acid is generated from phospholipid hydrolysis catalyzed by phospholipase. Its target is usually on another cell also, and it may activate protein kinase, resulting in phosphorylation of target molecules. Its target molecules are often involved in neural activities including learning.

The main role of steroids is in regulating transcription, and many steroid receptors are transcription factors (Overview, 2005). The bound steroid receptor may recruit steroid receptor coactivator (SRC) and histone acetyltransferase to stimulate transcription. In the absence of steroid, several steroid receptors may recruit corepressors (e.g. SMRT and NcoR) and histone deacetylase to repress transcription.

Ion channels are transmembrane proteins that allow ions to pass through (Overview, 2000). As to specificity, they are usually classified as calcium channels, sodium channels, potassium channels, etc. The channels may be volume-gated, ligand-gated, etc. The major ...

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Cells Communicating with their Environment. (1969, December 31). In LotsofEssays.com. Retrieved 08:35, March 29, 2024, from https://www.lotsofessays.com/viewpaper/1702901.html