Term
| What are pharmacokinetics? |
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Definition
| Factors determining the concentration of the ligand delivered to target sites e.g. route of administration, volume of distribution, metabolism, excretion, etc. |
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Term
| What are pharmacodynamics? |
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Definition
| Mechanisms by which drugs cause their effects once presented to their targets |
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Term
| What is the affinity of a ligand? |
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Definition
| The attractiveness of the ligand for the receptor. This can be thought of as how strong the ligand and receptor interact. The information encoding the affinity of this interaction is contained in the chemical structure of the ligand and the complimentary binding site on the receptor. Thus the structure of the ligand has a profound effect on its activity (structure-activity relationship). Forces mediating this interaction include Van der Waals, ionic, hydrogen bonds, hydrophobic, and covalent. |
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Term
| What is the specificity of a receptor? |
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Definition
| Classically, receptors interact with their ligands in a highly specific fashion. This characteristic is, in part, what determines the specific response elicited by the ligand in a whole organism. Again, information encoding the specificity of this interaction is encoded in the structures of the ligand and receptor (Again, the importance of the structure-activity relationship). |
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Term
| What are the characteristics of the classical Dose-Response Relationship? |
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Definition
1. Binding is directly proportional to ligand concentration. The concentration of ligand producing half-maximum occupancy (the Equilibrium Dissociation Constant, Kd) is a measure of ligand-receptor affinity
2. Responses are graded as opposed to quantal
3. Binding is saturable |
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Term
| What is the Quantitative Receptor Theory? |
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Definition
| Ligands and receptors bind to each other following the Laws of Mass Action. The forward reaction is bimolecular, dependent on the concentrations of ligand and receptor, while the reverse reaction is unimolecular, dependent on the concentrations of ligand-receptor complex only. At equilibrium, the rates of the forward and reverse reactions are equal. |
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Term
| What is the Equilibrium Dissociation Constant (Kd)? |
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Definition
[L][R]/[LR]
It is a measure of the affinity of the ligand for receptor. At equilibrium, it is the concentration of ligand yielding half-maximum occupancy of receptors.
A small Kd = high affinity
A large Kd = low affinity |
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Term
| What is a Scatchard plot? |
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Definition
| A plot of the bound/free ligand ([LR]/[L])versus bound ligand ([LR]). Should be linear with a slope of (-1/Kd) and an X intercept of Rt (Bmax). |
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Term
| What is adenylyl cyclase's second messenger? |
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Definition
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Term
| What is guanylyl cyclase's second messenger? |
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Definition
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Term
| What is Phospholipase C's second messenger? |
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Definition
| Phosphoinositol and diacylglycerol |
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Term
| In addition to graded, concentration-dependent, and saturable, what are the other 2 characteristics of Dose-Response graphs? |
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Definition
Potency - the concentration of ligand required to yield an effect; the concentration of a drug producing a half-maximum effect is EC50, analogous to Kd.
Efficacy - The ability to produce a biologic effect; Ligands with greater efficacy produce greater maximum biological effects (Emax) than those with lesser efficacy; This characteristic is related to the ability to activate effector mechanisms once bound to the receptor |
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