Signal transduction

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  1. What are the difficulties in transducing a signal outside the cell into a cellular response inside the cell?
    The cell membrane is impermeable to all but the most simple molecules.
  2. What are the two major classifications of signal transduction?
    membrane receptors and intracellular receptors. (inside and outside of the cell)
  3. What is a ligand?
    A ligand is a molecule that binds to a receptor.
  4. What is the property of ligands that accounts for the two major classifications of signal transduction?
    if it can not penetrate the cell it binds to a receptor outside of the cell. If it can then it is to an intracellular receptor.
  5. The three histamine receptors all bind histamine, but what are the differences in their response to histamine?
    • H1 - binds to the brain, smooth muscle and endothelium (blood vessels). Binding produces nasal and sinus secretions.
    • H2 - binds to the brain, cardiac muscles, stomach. binding produces gastric secretions.
    • H3- binds to the brain, other neurons
  6. Ciproxifan is a potent and specific histamine H3 receptor antagonist. Would it be expected that ciproxifan would alleviate allergy symptoms or suppress gastric acidity.
    Ciproxifan would reduce the affinity of the H3 receptor for histidine. H3 has no allergenic or gastric response, so it must have some other neurological effect.
  7. What are the three types of molecular switches for intracellular signaling?
    • GTP/GDP exchange
    • Kinase (adds a phosphate group)
    • Cyclase
  8. How are the actions of the "3 switches" reversed?
    • GTP/GDP exchange - hydrolysis
    • Kinase - phosphatase
    • Cyclase - phosphodiesterase
  9. Describe the effect of cholera toxin on signal transduction. Begin with how the toxin enters the cell and end with what the physiological consequences are.
    Cholera is an excess of signal transduction. Cholera's toxin binds to the ganglioside causing an increase in cAMP, increasing greatly the amount of intestinal secretions. 
  10. What molecule that is a precursor for a lipid involved in signal mediation of inflammation, blood clotting, control of vascular tone, pain, and fever is released from membranes by a phospholipase?
    arachidonic acid is cleaved which is a precursor for eicosanoids
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Signal transduction

Signal transduction
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