chapter 16 key terms cell communication

  1. adaptation
    adjustment of sensitivity of a cell or organism following repeated stimulation. can allow a response even when there is a high background level of stimulation.
  2. adenylyl cyclase
    enzyme that catalyzes the formation of cyclic AMP from ATP. An important component of some intracellular signaling pathways.
  3. Ca 2+/ calmodulin-dependent protein kinase (CaM-kinase)
    enzyme that phosphorylates target proteins in response to an increase in Ca2+ ion concentration, through its interaction with the Ca2+ binding protein calmodulin.
  4. calmodulin (CaM)
    small Ca2+ binding protein that modifies the activity of many target enzymes and membrane transport proteins in response to changes in Ca2+ concentration.
  5. cell signaling
    the molecular mechanisms by which cells detect and respond to external stimuli and send messages to other cells.
  6. cyclic AMP (cAMP)
    nucleotide generated from ATP in response to hormonal stimulation of cell-surface receptors. cAMP acts as a signaling molecule by activating protein kinase A; it is hydrolyzed to AMP by a phosphodiesterase.
  7. cyclic-AMP-dependent protein kinase (PKA)
    enzyme that phosphorylates target proteins in repsonse to a rise in intracellular cyclic AMP concentration.
  8. cytokine
    small protein made and secreted by cells that acts on neighboring cells to alter their behavior. cytokines act via cell-surface cytokine receptors.
  9. diacyglycerol (DAG)
    lipid produced by the cleavage of membrane inositol phospholipids in response to extracellular signals. composed of two fatty acid chains linked to glycerol, it serves as a membrane-located signaling molecule to help activate protein kinase C.
  10. enzyme-coupled receptor
    transmembrane receptor proteins that activate an intracellular enzyme (either a seperate enzyme or part of the receptor itself) in repsonse to lignad binding to the extracellular part of the receptor.
  11. extracellular signal molecule
    any molecule present outside the cell that can elicit a response inside the cell when the molecule binds to a receptor protein. some signal molecules, such as steroid hormones, can enter cells and act on internal receptors, whereas other, such as proteins, act at receptors embedded in the plasma membrane and exposed on the cell surface.
  12. G protein
  13. G-protein coupled receptor (GPCR)
    cell-surface receptor that associates with an intracellular trimeric GTP-binding protein (G protein) after receptor activation by an extracellular ligand. these receptors are sevenpass transmembrane proteins.
  14. GTP-binding protein
    an allosteric protein whose conformation and activity are determined by its association with either GTP or GDP. includes many proteins involved in cell signaling, such as Ras and G proteins.
  15. hormone
    a chemical substance produced by one set of cells in a multicellular organism and transported via body fluids to target tissues on which it exerts a specific effect.
  16. inositol phospholipids (phosphoinositides)
    minor lipid components of plasma membranes that contain phosphorylated inositol derivatives; important both for distinguishing different intracellular membranes and for signal transduction in eukaryotic cells.
  17. inositol 1,4,5-triphosphate (IP3)
    small intracellular signaling molecule produced during activation of the inositol phospholipid signaling pathway; causes Ca2+ release from the endoplasmic reticulum.
  18. ion-channel- coupled receptor
    transmembrane receptor protein or protein complex that forms a gated ion channel that opens in response to the binding of a ligand to the external face of the channel.
  19. intracellular signaling molecule
    molecule (usually a protein) that is part of the mechanism for transducing and transmitting signals inside a cell.
  20. intracellular signaling pathway
    the set of proteins and small-molecule second messengers that interact with each other to relay a signal from the cell membrane to its dinal destination in the cytoplasm or nucleus.
  21. local mediator
    secreted signal molecule that acts at a short range on adjacent cells.
  22. MAP kinase
    mitogen-activated protein kinase. protein kinase that performs a crucial step in relaying signals from cell-surface receptors to the nucleus. it is the final kinase in a three-kinase sequence called the MAP kinase casade.
  23. MAP-kinase signaling molecule
  24. molecular switch
    protein or protein complex that operates in aan intracellular signaling pathway and can reversibly switch between an active and inactive state.
  25. monomeric GTPase
    small, single-subunit GTP-binding protein. proteins of this family such as Ras and Rho, are part of many different signaling pathways.
  26. neurotransmitter
    small signaling molecule secreted by a nerve cell at a chemical synapse to signal to the postsynaptic cell. examples include acetylcholine, glutamate, GABA , and glycine.
  27. nitric oxide (NO)
    small highly diffusible molecule widely used as an intracellular signal.
  28. nuclear receptor
    receptor proteins present inside a eukaryotic cell that can bind to signal molecules that enter the cell, such as steroid hormones; the complex of nuclear recpetor annd signal molecule subsequently acts as a transcription regulator.
  29. phosphoinositide 3-kinase (PI 3-kinase)
    enzyme that phosphorylates inositol phospholipids in the plasma membrane in response to signals recieved by a cell. the phosphorylated lipids become docking sites for intracellular signaling proteins.
  30. phospholipase C
    enzyme associated with the plasma membrane that performs a crucial step in inositol phospholipid signaling pathways.
  31. protein kinase C (PKC)
    enzyme that phosphorylates target proteins in response to a rise in diacyglycerol and Ca2+ ions.
  32. protein phosphatase (phosphoprotein phosphatase)
    enzyme that removes, by hydrolysis, a phosphate group from a protein, often with high specificity for the phosphorylated site.
  33. Ras
    one of a large family of small GTP-binding proteins (also called the monomeric GTPases) that help relay signals from cell-surface receptors to the nucleus. named for the Ras gene, first identified in viruses that cause rat sarcomas.
  34. receptor
    a cell (such as the photoreceptor cells of the eye) or cellular component (such as a receptor protein) that detects an external signal and triggers a specific cellular response.
  35. receptor protein
    protein that detects a stimulus, usually a change in concentration of a specific molecule, and then initiates a response in the cell. cell-surface receptors, such as the acetylcholine receptor and the insulin receptor, are located in the plasma membrane, with their ligand-binding site exposed to the external medium. intracellular receptors, such as steroid hormone receptors, bind ligands that diffuse into the cell across the plasma membrane.
  36. receptor serine/threonine kinase
    enzyme coupled receptor with an extracellular signal binding domain and an intracellular kinase domain that phosphorylates signaling proteins pon serine or threonine.
  37. receptor tyrosine kinase (RTK)
    enzyme-coupled receptor in which the intracelllular domain has tyrosine kinase activity, which is activated by ligand binding to the receptor's extracellular domain.
  38. second messenger
    small molecule formed in or released into the cytosol in response to an extracellular signal that helps to relay the signal to the interior of the cell. examples include cAMP, IP3, and Ca2+.
  39. serine/theonine kinase
    enzyme that phosphorylates specific proteins on serines or threonines.
  40. signal transduction
    conversion of an impulse or stimulus from one physical or chemical form to another. in cell biology, the process by which a cell responds to an extracellular signal.
  41. small messenger
    see second messenger
  42. steroid hormone
    lipophilic molecule related to cholesterol that acts as a hormone. examples include estrogen and testosterone.
  43. tyrosine kinase
    enzyme that phosphorylates specific proteins on tyrosines.
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chapter 16 key terms cell communication
key terms from chapter 16