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Questions and Answers
What is the primary function of receptors in pharmacodynamics?
What is the primary function of receptors in pharmacodynamics?
What characterizes ligand-gated ion channels?
What characterizes ligand-gated ion channels?
Which type of receptor is coupled to a G protein?
Which type of receptor is coupled to a G protein?
What determines the effect of a drug on its target receptor?
What determines the effect of a drug on its target receptor?
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What describes a characteristic of lipid-soluble ligands?
What describes a characteristic of lipid-soluble ligands?
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In the key & lock model of receptor-ligand interaction, what does the 'key' represent?
In the key & lock model of receptor-ligand interaction, what does the 'key' represent?
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What is the duration of the response when a ligand binds to a ligand-gated ion channel?
What is the duration of the response when a ligand binds to a ligand-gated ion channel?
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Which type of receptor will typically lead to a slower response compared to others?
Which type of receptor will typically lead to a slower response compared to others?
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What mechanism causes the influx of Na+ and Ca2+ ions when a ligand binds to a receptor?
What mechanism causes the influx of Na+ and Ca2+ ions when a ligand binds to a receptor?
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Which type of ion channel opens due to physical distortion of the cell membrane?
Which type of ion channel opens due to physical distortion of the cell membrane?
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Which ion has a significantly higher concentration outside the cell compared to inside?
Which ion has a significantly higher concentration outside the cell compared to inside?
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What kind of receptor is characterized by having 7 transmembrane helices?
What kind of receptor is characterized by having 7 transmembrane helices?
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Which subunit of the G protein binds to guanosine diphosphate?
Which subunit of the G protein binds to guanosine diphosphate?
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Which type of ion channel opens and closes randomly without external stimuli?
Which type of ion channel opens and closes randomly without external stimuli?
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Which second messenger pathway is stimulated by Gs subtype of G protein?
Which second messenger pathway is stimulated by Gs subtype of G protein?
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What characteristic action do second messengers have in relation to GPCR signals?
What characteristic action do second messengers have in relation to GPCR signals?
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What is the primary role of G protein-coupled receptors (GPCR) upon ligand binding?
What is the primary role of G protein-coupled receptors (GPCR) upon ligand binding?
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Which second messengers are produced through the activation of phospholipase C (PLC)?
Which second messengers are produced through the activation of phospholipase C (PLC)?
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What cellular response duration is typically associated with enzyme-linked receptors?
What cellular response duration is typically associated with enzyme-linked receptors?
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Which of the following correctly describes the activation process of G proteins?
Which of the following correctly describes the activation process of G proteins?
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What is the mechanism of the insulin receptor after ligand binding?
What is the mechanism of the insulin receptor after ligand binding?
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What function does diacylglycerol (DAG) serve in the cellular signaling pathway?
What function does diacylglycerol (DAG) serve in the cellular signaling pathway?
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In which part of the cell are intracellular receptors typically located?
In which part of the cell are intracellular receptors typically located?
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Which of the following is a characteristic of responses mediated by G protein-coupled receptors?
Which of the following is a characteristic of responses mediated by G protein-coupled receptors?
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What is the primary role of transcription factors in relation to ligand-receptor complexes?
What is the primary role of transcription factors in relation to ligand-receptor complexes?
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Which of the following describes the action of Tamoxifen in breast cancer treatment?
Which of the following describes the action of Tamoxifen in breast cancer treatment?
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What is a characteristic feature of tachyphylaxis?
What is a characteristic feature of tachyphylaxis?
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What happens to receptors during receptor-mediated desensitization?
What happens to receptors during receptor-mediated desensitization?
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Which mechanism does not involve receptor-mediated changes?
Which mechanism does not involve receptor-mediated changes?
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What potential outcome can occur due to receptor down-regulation?
What potential outcome can occur due to receptor down-regulation?
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Which of the following roles does the ligand play in cellular signaling?
Which of the following roles does the ligand play in cellular signaling?
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What is a potential consequence of repeated drug administration?
What is a potential consequence of repeated drug administration?
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Study Notes
Pharmacodynamics: Receptors
- Receptors are cellular macromolecules that a ligand binds to initiate its effects
- Drugs bind and transduce extracellular signals to intracellular responses
- Receptors have specific binding sites for ligands (key & lock model)
- Drug effectiveness depends on two factors: affinity and intrinsic activity
- Affinity is the tendency to bind to the receptor to form a drug-receptor complex
- Intrinsic activity is the ability to trigger a response after forming a drug-receptor complex
Types of Receptors
- Ligand-gated ion channels
- Examples: cholinergic nicotinic receptors
- G protein-coupled receptors (GPCRs)
- Examples: alpha and beta adrenoceptors, insulin receptors
- Enzyme-linked receptors
- Examples: epidermal growth factor (EGF) receptors, insulin receptors
- Intracellular receptors
- Examples: steroid receptors
Major Receptor Types
- Ligands are generally hydrophilic or hydrophobic (lipophilic)
- Ligand-gated ion channels
- Located on cell membranes
- Open when activated by an agonist
- Rapid response (milliseconds)
- Examples: Nicotinic acetylcholine receptors
- Mechanically-gated ion channels
- Open in response to physical distortion of the cell membrane
- Examples: skin pressure/temperature changes
- Leakage ion channels
- Open and close randomly
- Contribute to the resting transmembrane voltage
G Protein-Coupled Receptors (GPCRs)
- Composed of 7 transmembrane helices
- Ligand-binding site is extracellular
- Intracellular domain is linked to a G protein
- G protein has three subunits: a, β, and γ
- GPCRs have different variants with different functions
- Examples: stimulate adenylyl cyclase or phospholipase C activity
- Second messengers (like cAMP) are essential for signal amplification
Enzyme-Linked Receptors
- Consist of proteins that can form dimers or multi-subunit complexes
- Ligand binding causes conformational change and increases cytosolic enzyme activity
- Specific proteins are phosphorylated
- Duration of responses is minutes to hours
- Examples: Epidermal growth factor (EGF) receptor, insulin receptor
Intracellular Receptors
- Receptors are entirely intracellular
- Ligands must be highly lipid-soluble to diffuse across the membrane
- Primary drug targets are transcription factors
- Activated ligand-receptor complexes translocate to the nucleus and bind to specific DNA sequences
- Influencing transcription and translation
- Duration of responses is hours to days
Comparison of Receptor Types
- Receptor types differ in activation mechanisms and duration of response
Desensitization and Down-Regulation of Receptors
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Repeated administration of a drug(agonist or antagonist) can change receptor responsiveness
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Tachyphylaxis: rapid desensitization, sometimes occurring with the initial dose
-
Desensitization mechanisms:
- Receptor-mediated
- Change in receptor conformation
- Example: phosphorylation of specific amino acids (aas) blocks coupling of G proteins
- Non-receptor-mediated
- Decrease in signaling components (e.g., depletion of second messengers)
- Increase in metabolic degradation (e.g., increased metabolism or elimination)
- Receptor-mediated
-
Down regulation: decreased number of receptors (internalization into the cell)
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Description
Explore the fundamental concepts of pharmacodynamics, focusing on receptors and their interaction with ligands. This quiz covers various types of receptors, including GPCRs and ligand-gated ion channels, as well as key factors such as affinity and intrinsic activity. Test your knowledge on how drugs communicate signals within cells.
