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47 Cards in this Set
- Front
- Back
2 major types of receptors
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ionotropic and metabotropic
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Define ionotropic receptors
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ligand gated ion channels
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Define metabotropic receptors
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ligand-induced second messenger generators that alter the "metabolism" of the cell
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which receptor has fast onset and termination
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ionotropic
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Which receptor shows amplification of response and diversity
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metabotropic
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are there transmitters that bind to both iono and metabotropic receptors
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yes, Ach, GABA, Glutamate
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Describe location of ionotropic and metabotropic receptors
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ionotropic are often located near transmitter release sites, metabotropic are usually not near transmitter release sites
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Name Ach ionotropic receptor
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nicotinic
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Name Ach metabotropic receptor
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muscarinic
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name model organism for study of nicotinic Ach receptors
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electric organ of Torpedo electric fish
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How many subunits are there in nAchR
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5 subunits - 2 alpha, beta, gamma and delta, all 5 subunits form staves on barrel arrangement
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Describe subunit of nAchR
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4 regions (M1-M4), M2 from each subunit forming lining of pore
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Which subunit has binding sites for transmitter
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alpha subunits
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What happens when Ach binds to receptor
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if only one Ach binds will have brief flickering, if 2 Ach bind will have normal opening
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Name toxins that block Ach binding
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alpha bungarotoxin/curare
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describe ion selectivity of Ach receptors
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multi ion selectivity - equally permeable to Na and K. some permeability to Ca, depends on alpha subunit 7
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what is the equilibrium potential of Ach receptor
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0 mV
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Name 2 classes of glutamate receptors
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NMDA and non NMDA
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What NMDA stands for
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N mmethyl D aspartate
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Describe NMDA receptor
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-activated by NMDA agonist
- high conductance (50 pS) -permeable to Ca, Na, K -pore is plugged by Mg at resting potential, plug is removed by depolarization -relatively slow gating -lots of modulatory sites (glycine, Zn, PCP) |
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Name 2 classes of non NMDA receptors
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AMPA and kainate
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Describe non NMDA receptor
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-lower conductance (20 pS)
-permeable mostly to only Na and K -fast gating |
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what is the most common inhiitory NT
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GABA, inhibitory because does not conduct Na or K , but Cl, used by many interneurons
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Ionotropic GABA receptor is..
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ligand gated Cl channel
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Chloride is _ outside, _ inside
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high, low
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Equilibrium potential for Cl channel
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-70
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Pertussis toxin
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travels across cell membrane and inactivates galpha i protein and g alpha 0 , uncouples and prevents action of metabotropic receptor
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what happens if add NT and receptor is metabotropic
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will inhibit activity
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what effects which pathway you chose
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primary effector effects, not g protein or receptor
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Direct pathway
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g protein directly associates with final receptor
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what is most common direct pathway
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beta gamma
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How do you know beta gamma acts on K channel directly
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use reconstitution, overexpress K channels
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How many subunits does g protein have
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3 subunits - alpha beta gamma
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describe g protein in resting state
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all three subunits associate with each other and receptor, alpha subunit binds GDP (high affinity)
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what happens to g protein when NT binds
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it loses affinity for GDP, and binds GTP since its more abundant, alpha dissociates from beta and gamma
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How does alpha subunit inactivate
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it turns itself off since it is a slow GTPase, when GTP is cleaved back to GDP, complex reassociates and protein returns to active state
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what experiments can be done to prove GTP is used
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1) remove GTP
2)replace GTP with GTP gamma s which is non hydrolyzable form and will cause persistent activation 3)replace with GDP beta s which has high affinity binding to alpha subunit of g protein will causes block of signaling |
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what determines diversity and specificity of actions
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1. specific g protein receptor interactions
2.use of either beta gamma or alpha subunits 3 diverse second messenger cascades |
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Specific g protein receptor interactions
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there are 20 alpha, 5 beta 7 gamma subunits, allows number of combinations
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Describe antisense oligonucleotides experiment
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inject into cells sequence of about 20-30 amino acids that is complimentary to MRNA that codes for g protein. When bound, mRNA will be double stranded and will not be translated into protein, after time protein will be depleted
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Both somatostatin and Ach reduce Ca, is it same g protein
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no, uses different alpha, beta and gamma subunits, this may reduce crosstalk , allows for specificity
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Receptor signaling compartmentalization
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receptor , g proteins and interacting proteins are all within different compartments of the cell
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General scheme of messenger action
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First messenger-->receptor-->transducer-->primary effector-->second messenger--> secondary effector
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what does activation of muscarinic receptors do in heart cells
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opens K+ channels causing hyperpolarization and decreasing heart rate
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How do you do reconstitution
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inject oocyte with GIRK channels and g protein subunits
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what happens when you express beta gamma RNA with GIRK channel but exclude GTP
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doesnt block beta gamma effect
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same but add GDP beta s
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doesnt block beta gamma effect
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