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Paper Topic:

signal transduction in cells

Signal Transduction

Cells are not only the smallest units of life ' but they also depict the best machineries in the world . Cells not only work exceptionally well within their own systems but coordinate efficiently with other cells in to ensure their survival . Reactivity , which refers to the living thing 's ability to respond to signals from the environment enables the organism to react to various stimuli , either behaviorally or physiologically ( HYPERLINK "http /www .okstate .edu /artsci /zoo_home /zoo_lrc /1114www /life /life .htm The Characteristics of Life . Signals come in various forms such

as changes in temperature , illumination , pressure and even intercellular chemical concentration . Other signals which take subtler forms are those which signal either cell division or cell differentiation . Protective responses are also carried out by most cells whenever foreign substances intrude the organism 's body . Such feats are only possible through signaling systems which are either intracellular or intercellular HYPERLINK "http /www .biology .arizona .edu /CELL_BIO /problem_sets /signaling /Index .ht ml " The Cell Signaling Test ) and are generally referred to as signal transduction pathways

Signal transduction figures in information metabolism . Information metabolism refers to the cell 's reception , processing and consequent response to information from the environment (Signal Transduction Pathways : An Introduction to Information Metabolism . At the cellular level , signal transduction refers to the movement of signals from the outside to the inside of the cell . The process through which signal transduction occurs varies depending upon the nature of chemicals and their associated receptors . Signal movement can be as simple as those which involve the receptor molecules of the acetylcholine class or can be as complex as those which involve combinations of ligand - receptor interactions and several intracellular events . In the case of simple signal transduction , signals pass in or out of the cell through receptors which are mainly composed of channels . The process is effected out by ligand interaction through the form of small ion movements . These ion movements in turn result to changes in the cell 's electrical potential and consequently , to the propagation of the said signal along the cell (Mechanisms of Signal Transduction . Complex signal transduction , as mentioned before , does not only involve ligand interactions but also several intracellular events . These events include phosphorylations induced by the enzymes tyrosine kinases and /or serine /threonine kinases . Protein phosphorylations are specifically helpful in understanding the process of gene expression since they influence , to a large extent , enzymatic activities and protein conformations (Mechanisms of Signal Transduction

Pathways of signal transduction could therefore be depicted as molecular circuits . A pathway typically begins with the transfer of information from the environment towards the cell 's internal system Nonpolar molecules (steroid hormones such as estrogen ) could easily penetrate the cell membrane and could therefore , enter the cell . Once inside the cell , these molecules bind to proteins and interact with the cell 's DNA . The consequence of this interaction is that the molecules directly influence gene transcription . Other molecules , such as those which are too large or too polar , are not...

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