L 4 Flashcards
Q: What is the correct definition of a receptor?
A protein that is activated by an agonist (naturally found in the body)
Produces a physiological response
Can interact with antagonists
Q: What is the difference between affinity and efficacy in drug-receptor interactions? A:
Affinity: The tendency of a drug to bind to a receptor.
Efficacy: The tendency of a drug to activate the receptor.
Q: What type of drugs have both affinity and efficacy?
A: Agonists.
What is receptor desensitization?
A gradual decrease in receptor responsiveness to an agonist, often caused by prolonged exposure.
: What do antagonists possess: affinity or efficacy?
A: Antagonists have affinity but no efficacy.
How is receptor desensitization achieved in GPCRs?
By phosphorylation of the receptor, rendering it inactive.
What happens during receptor downregulation?
Prolonged exposure to agonists results in a decrease in the number of receptors on the cell surface, typically removed by endocytosis.
What is LD50
LD50 (Median Lethal Dose) is the dose required to kill 50% of the test animals.
What are the four types of toxicity tests based on exposure time?
- Acute Toxicity: Single exposure.
- Sub-acute Toxicity: Repeated doses, up to 14 days.
- Sub-chronic Toxicity: Repeated doses, up to 90 days.
- Chronic Toxicity: Continuous exposure for more than 90 days.
What are the categories of toxicity based on LD50?
- Extremely toxic: LD50 < 1 mg/kg
- Highly toxic: LD50 < 50 mg/kg
- Moderately toxic: LD50 < 500 mg/kg
- Slightly toxic: LD50 > 500 mg/kg
What is the difference between toxicity and hazard?
Toxicity is the degree to which a substance can cause harm.
Hazard is the actual risk of poisoning, taking into account exposure levels.
What can increase or decrease toxicity in mixed substances?
Synergism: Toxicity increases.
Antagonism: Toxicity decreases.
What does the binding capacity (Bmax) represent?
A: The density of receptors (or binding sites) in the tissue when all receptors are occupied by the drug (saturation).
KA (affinity constant) is determined by which two binding rates? A:
K+1: Rate of drug binding to the receptor
K-1: Rate of drug dissociating from the receptor
Q: What does a high KA number signify about a drug’s affinity?
A: A high KA number signifies low affinity for the receptor.
What is the difference between full and partial agonists? A:
Full agonists: Produce a maximal response.
Partial agonists: Produce a sub-maximal response.
How do competitive antagonists work? A:
Competitive antagonists compete with agonists for the same binding site on the receptor.
How do non-competitive antagonists work?
A: Non-competitive antagonists reduce the response by blocking part of the signal transduction pathway, without competing for the receptor binding site.
