Cells & the 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 a

Related Essays

Cells Communicating with their Environment Cells need to communicate with their environment so they can respond appropriately (Overview, 2005). The external signal to the .... (1622 6 )

Place cells .... pyramidal cells, and they derive their name from the fact that they only fire when an animal is in the cell's firing field, ie in a part of its environment .... (2638 11 )

Place Cells .... pyramidal cells, and they derive their name from the fact that they only fire when an animal is in the cell's firing field, ie in a part of its environment .... (2638 11 )

Brain Cells in Embryos, Fetus, Infants, Young Children .... the 17th week of pregnancy, the fetus has about 1 billion brain cells, and they .... feel secure, and can then devote time to exploring their environment, but those .... (3338 13 )

Genetics & Environment .... by the environment...and the most important feature of the environment for an infant is .... On examining cells from each rat's hippocampus, the region of the brain .... (1974 8 )

s. Small G proteins such as Ras, Rac and Rap activate MAPKKK, the kinase of MAPKK, to produce the MAPKK which is the kinase of MAPK, and produces MAPK. Three major MAPK pathways have been identified in mammals: MAPK/ERK, SAPK/JNK and p38 MAPK. Receptors are complex molecules which interact specifically with certain substances in the environment (Agullo, 2005). After binding of these substances, receptors undergo an alteration of their tridimensional structure which results in the production of enzymes which changes the concentration of certain molecules within the cell, known as second messengers, which mediate the final response of the cell to the environmental modification detected by the receptor. Sometimes the receptors synthesize the second messengers, but more often other complex molecules that interact with the receptors are needed to produce the second messengers. There are three general types of signal transducing receptors (King, 2004). The first is receptors that penetrate the plasma membrane and have intrinsic enzymatic activity, such as the tyrosine kinases (PDGF, insulin, EGF and FGF receptors), tyrosine phosphatases (CDA45 protein of T cells and macrophages), guanylyl cyclases (natriuretic peptide recepto

Category: Science - C