chapter 11 - Cell Communication Cell Signaling...

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1 Cell Communication Cell Signaling Signal-transductio n Æ signal on a cell’s surface is converted into a cellular response Similarities in chemical pathways between prokaryotes and eukaryotes suggest ancient origin of cell signaling origin of cell a-factor and alpha-factor yeast cells Saccharomyces secrete complementary signals Exchange of mating factors Mating Receptor a α α factor a factor Yeast cell, mating type a Yeast cell, mating type α 1 each cell secretes a mating factor that a α a/ α New a/ α cell binds to receptors on the other cell 2 biding factors lead to cell fusion 3 the new fused nucleus has a+alpha genes Local and Long-Distance Signaling Local signaling Æ in situ communication between nearby cells (“ direct ” signaling) Long-distance Æ ex situ communication between distant cells (“ indirect ” signaling) Direct-contact communication between cells Plasma membranes Gap junctions between animal cells Plasmodesmata between plant cells Cell-cell recognition (a) Gap junctions and plasmodesmata passage of molecules between adjacent cells (b) Ligand molecules are recognized by membrane receptors in cell-to-cell recognition
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2 Local and long-distance signaling among animal cells secretory vesicle secreting cell target cell Local signaling release of neurotransmitter neurotransmitters in synapse endocrine cell blood vessel Long-distance signaling hormone travels ib l dt Paracrine signaling regulator diffuses in extracellular fluid in bloodstream Synaptic signaling target cell is stimulated Hormonal signaling target cell secreting cell discharges regulator molecule via exocytosis nerve cells release neurotransmitters into synaptic cleft: pre Æ post synaptic cells (exocytosis) endocrine glands secrete hormones into body fluids exocytosis Stages of Cell Signaling Reception Æ cell detects a signal molecule coming from outside ( ligand-receptor binding in cell membrane Æ CM) Transduction Æ signal is converted to a form (ions molecules) that initiates a cascade of (ions, molecules) that initiates a of chemical reactions Response Æ cytoplasm and/or nucleus: cytoplasm : cytosol activities nucleus : gene activity EXTRACELLULAR FLUID Reception Plasma membrane Transduction CYTOPLASM Receptor Signal molecule EXTRACELLULAR FLUID Reception Plasma membrane Transduction CYTOPLASM Receptor Signal molecule Relay molecules in a signal transduction pathway EXTRACELLULAR FLUID Reception Plasma membrane Transduction CYTOPLASM Receptor Response Activation of cell lar Signal molecule Relay molecules in a signal transduction pathway of cellular response Reception: a signal molecule binds to a receptor protein causing it to change Binding between signal molecule ( ligand ) and receptor Æ highly specific Ligand-receptor binding Æ conformational change of receptor Æ initiates transduction Most signal receptors are CM proteins Some are intracellular receptors (cytosol, nucleus)
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3 Receptors in the Plasma Membrane
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chapter 11 - Cell Communication Cell Signaling...

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