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18 Cards in this Set
- Front
- Back
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What is a ligand?
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A small molecule which binds to a site on a receptor and may be endogenous or exogenous.
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What are 3 types of cell surface receptors?
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Ligand-gated ion channel
G-protein coupled receptor Enzyme-linked receptor |
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What is the equation for saturation of receptors?
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B = [L]
Bmax Kd+[L] |
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What is Kd?
D should be uppercase |
Dissociation constant - concentration of ligand at which half the available receptors are occupied
= affinity of the ligand |
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Compare a ligand with a low dissociation constant with one with a high one
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Higher affinity for receptor
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What is the equation for physiological response?
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R = [L]
Rmax EC50 + [L] |
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What is EC50?
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Concentration of ligand that gives 50% of maximal response
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What are reasons for plotting a logarithmic graph?
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Spreads out experimental points of lower half of graph, allows EC50/Kd to be estimated, sigmoid curve produced
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How will spare receptors affect EC50 and Kd?
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EC50<Kd
As full response could be achieved without binding all of receptors |
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What is EC50 dependent on?
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Amount of receptor and ligand
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What is upregulation?
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Increase in receptor number
Makes response more sensitive |
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What are agonists/antagonists to receptors?
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Agonists bind to receptors and cause response
Antagonists bind to receptors without activating |
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What is efficacy?
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Activation of receptor site
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Describe what would happen to the graph with a competitive antagonist
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Graph would shift to right
Antagonist overcome by increasing L |
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What would happen to the graph with an irreversible antagonist?
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Initial shift to the right, but when spare receptors are occupied, maximal response decreased
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What would happen to the graph with a higher/lower affinity agonist?
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Higher - curve shifts to left
Lower - curve shifts to right Maximal response is the same but may take more or less drug to achieve |
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What would happen to the graph with a partial agonist?
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Maximal response reduced even at full occupancy
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What happens in binding with a full and partial agonist?
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Full - only binds to active receptors and produces a response
Partial - binds to inactive receptors (no response) and to active receptors (response) |
