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In many transduction processes, an increasing number of enzymes and other molecules become engaged in the events that proceed from the initial stimulus. In such cases the chain of steps is referred to as a " signalling cascade " or "second messenger pathway" and the result is that a small stimulus elicits a large response.
In bacteria and other one-cell organisms, the variety of signal transduction processes of which the cell is capable influences how many ways it can react and respond to its environment. In a less direct way the same is true of animals and plants. Sensing in all forms of life depends, at the cellular level, on signal transduction.
The environment of a cell may impinge on it in many ways: different kinds of molecules may buffet its surface, its body may be heated or cooled, it may be struck by light of various wavelengths, stretched, sheared or electrified (the nerves and muscles, for example). Signal transduction mediates how cells respond to such stimuli.
Most stimuli impinge from the outside and interact with the cell membrane. Many "signaling molecules," such as the neurotransmitterA neurotransmitter is a type of molecule that carries signals between neurons (nerve cells) at synapses in the nervous system. Neurotransmitters may be either excitatory ( EPSPs) or inhibitory ( IPSPs). That is, they may foster the initiation of a nerve is that allow nerve cellsNeurons (also called nerve cells are the primary cells of the nervous system. In vertebrates, they are found in the brain, the spinal cord and in the nerves and ganglia of the peripheral nervous system. Classes There are three classes of neurons: afferent to communicate across synapsenerve cells to communicate with one another through axons and dendrites, converting electrical signals into chemical ones. For the technology festival, see Synapse Festival. Synapses are specialized junctions through which cells of the nervous system signs, bind to receptor proteinsTransmembrane receptors are integral membrane proteins, which reside and operate typically within a cell's plasma membrane, but also in the membranes of some subcellular compartments and organelles. Binding to a signalling molecule or sometimes to a pair in the membrane and open portalsIon channels are present in the membranes that surround all biological cells. By conducting and controlling the flow of ions, these pore-forming enzymes help establish the small negative voltage that all cells possess at rest (see cell potential). Basic f in it.
Responses triggered by signal transduction include the activationTranscription may be one of the following: In linguistics, transcription is the conversion of spoken words into written language. In genetics, transcription is the process of copying DNA to RNA by an enzyme called RNA polymerase (RNAP). In music transcrip of a geneDNA and to a chromosome (right). Introns are regions often found in eukaryote genes which are removed in the splicing process: only the exons encode the protein. This diagram labels a region of only 40 or so bases as a gene. In reality many genes are much, the production of metabolic energyCell metabolism is the process (or really the sum of many ongoing individual processes) by which living cells process nutrient molecules and maintain a living state. Metabolism has two distinct divisions: anabolism in which a cell uses energy and reducing and cell locomotion, for example through remodelling of the cell skeleton.
Gene activation leads to further effects, since genes are expressed as proteins, many of which are enzymes, transcription factors or other regulators of metabolic activity. Because transcription factors can activate still more genes in turn, an initial stimulus can trigger via signal transduction the expression of entire suite of genes and a panoply of physiolgical events. Such mass activations are often referred to as " genetic programs," one example being the sequence of events that take place when an egg is fertilized by a sperm.