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Chapter 11 Notes - Chapter 11 Cell Communication External...

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Chapter 11 Cell Communication External signals There are two sexes or mating types o A and alpha Cell matting type a secrete a signaling molecule call a factor, which bind to specific receptor proteins on nearby cells alpha Alpha cell secretes alpha factor which binds to receptors on cell a Result is the fusion or mating of two cells of different types o Signal transduction pathway A process by which a signal on a cell’s surface is converted to a specific cellular response is a series of steps The concentration of such signaling molecules allows bacteria to sense the local density of bacterial cells called quorum sensing Signaling o Animal and plant cells use junctions that are present in the cytoplasm to communicate o Local regulators- travel short distances to influence cells in the vicinity Animals local signaling called paracrine signaling Chemical signal carried by the neurotransmitter diffuses across the synapse, between the cells o Long distance Animal and plants use chemical hormones Endocrine signaling, specialized cells release hormone molecules The transmission of a signal through the nervous system can be considered long- distance signaling o Stages of signaling Reception- is the targets cell’s detection of a signaling molecule coming from the outside the cell Transduction- the binding of the signaling molecule changes the receptor protein in some way Sometimes occurs in a single step But often required a sequence of changes in a series of different molecules – a signal transduction pathway Response- the transduced signal finally triggers a specific cellular response. Reception o A receptor protein on or in target cell allows the cell to hear the signal and respond to it. o The signaling molecule is complementary in shape to a specific site on the receptor and attaches there o Ligand- a molecule that specifically binds to another molecule, often one larger Causes the receptor protein to undergo a change o Most signal receptors are plasma membrane proteins
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Ligands are water soluble and generally too large to pass freely through the
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