11 - Cell Transduction II

11 - Cell Transduction II - Signal Transduction II...

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Signal Transduction II
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G-proteins associated with GPCRs and G- proteins that regulate nuclear import and export are similar because (A) Both have different conformations in GTP and GDP-bound states (B) Both have GAP proteins that activate GTP hydrolysis (C) Both have GEF proteins that help to exchange GDP to GTP (D) All of the above (E) None of the above
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Quiz The key differences between second messengers and ligands for receptors are: (A) Second messengers are hydrophilic and regulate cytosolic proteins (B) Second messengers have short half-life (C) Ligands for receptors can not cross the membrane and enter the cell (D) None of the above (E) All of the above
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GPCRs that directly regulate ion channels GPCRs that indirectly regulate ion channels (2 messenger: cGMP) GPCRs that work through adenylyl cyclase (2 messenger: cAMP) GPCRs that work through phospholipase C (2 messengers: Ca 2+ , IP3, DAG) Muscarinic Acetylcholine receptor Rhodopsin Different types of GPCRs
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In the dark the membrane is depolarized that generates constant signals to neurons. Depolarized state is caused by open nonselective ion channels (allows Na and Ca inside) Channels are open because of high level of cytoplasmic cGMP. Light close the channels by decreasing cGMP concentration that is hydrolyzed by phosphodiesterase (PDE) that activated by G α Closing the channels polarize the membrane that stop the signal to neurons Signal amplification : 1 photon -> 1 activated opsin molecule -> 500 activated G α -> … one photon can be detected on cellular level and 5 photons is enough for humans to see the light GPCRs that regulate ion channels. Indirect interaction. Light detection by rhodopsin. Smell (olfactory) pathway is very similar
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GPCRs that regulates adenylyl cyclase In reality, they work through different GPCRs
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cAMP activates cAMP-dependent protein kinase (also known as Protein kinase A or PKA) cAMP activates PKA by binding to inhibitory
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This note was uploaded on 01/12/2012 for the course BI 9 taught by Professor Aravin during the Spring '10 term at Caltech.

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11 - Cell Transduction II - Signal Transduction II...

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