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Question 1

Q: What is the correct definition of a receptor?

Answer 1

A protein that is activated by an agonist (naturally found in the body)
Produces a physiological response
Can interact with antagonists

Question 2

Q: What is the difference between affinity and efficacy in drug-receptor interactions? A:

Answer 2

Affinity: The tendency of a drug to bind to a receptor.
Efficacy: The tendency of a drug to activate the receptor.

Question 7

Q: What type of drugs have both affinity and efficacy?

Answer 7

A: Agonists.

Question 9

What is receptor desensitization?

Answer 9

A gradual decrease in receptor responsiveness to an agonist, often caused by prolonged exposure.

Question 10

: What do antagonists possess: affinity or efficacy?

Answer 10

A: Antagonists have affinity but no efficacy.

Question 10

How is receptor desensitization achieved in GPCRs?

Answer 10

By phosphorylation of the receptor, rendering it inactive.

Question 11

What happens during receptor downregulation?

Answer 11

Prolonged exposure to agonists results in a decrease in the number of receptors on the cell surface, typically removed by endocytosis.

Question 12

What is LD50

Answer 12

LD50 (Median Lethal Dose) is the dose required to kill 50% of the test animals.

Question 13

What are the four types of toxicity tests based on exposure time?

Answer 13

1. Acute Toxicity: Single exposure.
2. Sub-acute Toxicity: Repeated doses, up to 14 days.
3. Sub-chronic Toxicity: Repeated doses, up to 90 days.
4. Chronic Toxicity: Continuous exposure for more than 90 days.

Question 13

What are the categories of toxicity based on LD50?

Answer 13

1. Extremely toxic: LD50 < 1 mg/kg
2. Highly toxic: LD50 < 50 mg/kg
3. Moderately toxic: LD50 < 500 mg/kg
4. Slightly toxic: LD50 > 500 mg/kg

Question 14

What is the difference between toxicity and hazard?

Answer 14

Toxicity is the degree to which a substance can cause harm.
Hazard is the actual risk of poisoning, taking into account exposure levels.

Question 15

What can increase or decrease toxicity in mixed substances?

Answer 15

Synergism: Toxicity increases.
Antagonism: Toxicity decreases.

Question 16

What does the binding capacity (Bmax) represent?

Answer 16

A: The density of receptors (or binding sites) in the tissue when all receptors are occupied by the drug (saturation).

Question 17

KA (affinity constant) is determined by which two binding rates? A:

Answer 17

K+1: Rate of drug binding to the receptor
K-1: Rate of drug dissociating from the receptor

Question 18

Q: What does a high KA number signify about a drug’s affinity?

Answer 18

A: A high KA number signifies low affinity for the receptor.

Question 19

What is the difference between full and partial agonists? A:

Answer 19

Full agonists: Produce a maximal response.
Partial agonists: Produce a sub-maximal response.

Question 20

How do competitive antagonists work? A:

Answer 20

Competitive antagonists compete with agonists for the same binding site on the receptor.

Question 21

How do non-competitive antagonists work?

Answer 21

A: Non-competitive antagonists reduce the response by blocking part of the signal transduction pathway, without competing for the receptor binding site.