10) - Cells in a multicellular organism communicate by...

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Cells in a multicellular organism communicate by chemical messengers Animal and plant cells have cell junctions that directly connect the cytoplasm of adjacent cells In local signaling, animal cells may communicate by direct contact, or cell-cell recognition In many other cases, animal cells communicate using local regulators , messenger molecules that travel only short distances In long-distance signaling, plants and animals use chemicals called hormones Fig. 11-5 The Three Stages of Cell Signaling (Fig. 11-6-1, 2, 3) Earl W. Sutherland discovered how the hormone epinephrine acts on cells Sutherland suggested that cells receiving signals went through three processes: o Reception o Transduction o Response Reception: A signal molecule binds to a receptor protein, causing it to change shape The binding btwn a signal molecule ( ligand ) and receptor is highly specific A shape change in a receptor is often the initial transduction of the signal Most signal receptors are plasma membrane proteins or glycoproteins Receptors in the Plasma Membrane Most water-soluble signal molecules bind to specific sites on receptor proteins in the plasma membrane There are three main types of membrane receptors: G protein-coupled receptors Receptor tyrosine kinases Ion channel receptors A G protein-coupled receptor is a plasma membrane receptor that works with the help of a G protein The G protein acts as an on/off switch: If GDP is bound to the G protein, the G protein is inactive Intracellular Receptors
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Some receptor proteins are intracellular, found in the cytosol or nucleus of target cells Small or hydrophobic chem. messengers can readily cross the membrane and activate receptors
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10) - Cells in a multicellular organism communicate by...

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