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pharmacology > Drugs and Receptors > Flashcards

Drugs and Receptors Flashcards

1
Q

drugability

A
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2
Q

what are drug targets

A
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3
Q

what is a receptor

A
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4
Q

Name three types of chemicals that communicate via receptors.

A

Neurotransmitters, Autacoids (local), and Hormones.

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5
Q

Give two examples of neurotransmitters.

A

Acetylcholine and serotonin.

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6
Q

What does “autacoid” mean, and give two examples.

A

“Autacoid” comes from Greek words meaning “self” (autos) and “relief” (acos); examples are cytokines and histamine.

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7
Q

Provide two examples of hormones that communicate through receptors.

A

Testosterone and hydrocortisone.

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8
Q

What are the four main types of receptors?

A
  • G-protein-coupled receptors (GPCRs)
    These are the largest and most diverse group of cell surface receptors in eukaryotes. They receive messages in the form of light energy, peptides, lipids, sugars, and proteins.
  • Ligand-gated ion channels
    These receptors are a vital component of nervous system signaling. They convert a chemical neurotransmitter message to an electrical current.
  • Enzyme-linked receptors
    These cell-surface receptors have intracellular domains that are associated with an enzyme. When a ligand binds to the extracellular domain, it activates the enzyme, which sets off a chain of events within the cell.
  • Cell-surface receptors
    Also known as transmembrane receptors, these receptors are involved in most of the signaling in multicellular organisms. They convert an extracellular signal into an intracellular signal
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9
Q

Give an example of a ligand-gated ion channel receptor.

A

Nicotinic ACh receptor.

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10
Q

What is an example of a G protein-coupled receptor?

A

Beta-adrenoceptors.

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11
Q

What type of receptors are kinase-linked receptors associated with?

A

Receptors for growth factors.

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12
Q

What is an example of a cytosolic/nuclear receptor?

A

Steroid receptors.

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13
Q

What are ion channels?

A

Ion channels are pore-forming membrane proteins that allow ions to pass through, causing a shift in electric charge distribution.

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14
Q

What types of ions can mediate changes in charge through ion channels?

A

Cations (+ve) for influx and anions (-ve) for efflux.

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15
Q

What happens when a ligand-gated ion channel is activated?

A

The channel opens, allowing ions to flow in or out of the cell.

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16
Q

What is the role of a receptor in ligand-gated ion channels?

A

The receptor binds to a messenger (ligand), triggering the opening of the channel.

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17
Q

What are GPCRs?

A

GPCRs (G protein-coupled receptors) are the largest and most diverse group of membrane receptors in eukaryotes.

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18
Q

How many membrane-spanning regions do GPCRs have?

A

GPCRs have 7 membrane-spanning regions.

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19
Q

What percentage of genes are GPCRs thought to make up?

A

About 4% of all genes.

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20
Q

What percentage of drugs target GPCRs?

A

Over 30% of drugs.

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21
Q

What types of ligands activate GPCRs?

A

Ligands include light energy, peptides, lipids, sugars, and proteins.

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22
Q

What are G proteins?

A

G proteins, or guanine nucleotide-binding proteins, are a family of proteins involved in transmitting signals from GPCRs. Humans have 35 types.

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23
Q

How is the activity of G proteins regulated?

A

By factors that control their ability to bind and hydrolyse GTP (guanosine triphosphate) to GDP (guanosine diphosphate).

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24
Q

What role do G proteins (GTPases) play?

A

They act as molecular switches, catalysing the exchange of GDP to GTP when a ligand binds to GPCRs.

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25
Q

What happens when GTP binds to a G protein?

A

It activates downstream signalling pathways.

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26
Q

what do the majority of GRCRs interact with

A

The majority of GPCRs interact with PLC or adenylyl cyclase

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27
Q

What are kinase-linked receptors?

A

are enzyme that catalyze the transfer of phosphate groups between proteins - process is known as phosphorylation.

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28
Q

What is the role of kinases in kinase-linked receptors?

A

Kinases catalyse the transfer of phosphate groups between proteins, a process called phosphorylation.

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29
Q

What does the substrate gain during phosphorylation?

A

A phosphate group “donated” by ATP.

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30
Q

What happens after ligand binding in kinase-linked receptors?

A

Tyrosines in the receptor are phosphorylated, creating docking sites for intracellular proteins.

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31
Q

What do nuclear receptors do?

A

Nuclear receptors work by modifying gene transcription.

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32
Q

How do nuclear receptors bind to DNA?

A

Through zinc fingers, which interact with specific DNA sequences.

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33
Q

What is Tamoxifen, and what does it do?

A

Tamoxifen is a selective estrogen receptor modulator (SERM) that acts as a partial agonist of estrogen receptors, used in ER+ cancers such as breast cancer.

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34
Q

How can an imbalance of chemicals cause disease?

A
  • Too much histamine can cause allergies.
  • Too little dopamine can lead to Parkinson’s disease.
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35
Q

How can an imbalance of receptors cause disease?

A
  • Losing acetylcholine (ACh) receptors causes muscle weakness in myasthenia gravis.
  • Too many active c-kit receptors cause abnormal mast cell behaviour in mastocytosis.
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36
Q

Why is targeting imbalances in chemicals or receptors a useful medical approach?

A
  • Because correcting these imbalances can help treat or manage the related diseases.
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37
Q

Why is receptor characterization important in developing treatments?

A

It helps identify the receptor involved in a disease process.

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38
Q

What is the next step after identifying a receptor involved in a disease?

A

Develop drugs that target that specific receptor.

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39
Q

How is the effectiveness of a drug at a receptor measured?

A

By quantifying the drug’s action at that receptor.

40
Q

What is an agonist?

A

A compound that binds to a receptor and activates it.

41
Q

What is an antagonist?

A

A compound that reduces the effect of an agonist by blocking the receptor.

42
Q

What happens when both an agonist and an antagonist bind to a receptor?

A

The receptor’s activation is reduced compared to when only an agonist is present.

43
Q

What is a ligand?

A

A molecule that binds to another (usually larger) molecule, such as a receptor.

44
Q

two state model of receptor activation

A
45
Q

What does the log concentration-response curve show?

A

It demonstrates the relationship between increasing drug concentration and the percentage of the maximal response, typically sigmoidal in shape.

46
Q

What does EC50 represent in a drug’s potency?

A

EC50 is the concentration of a drug required to produce 50% of the maximal response.

47
Q

How is the potency of two drugs compared using dose-response curves?

A

By determining which drug requires a lower concentration to achieve the same response, indicating higher potency.

48
Q

How do partial agonists compare to full agonists in efficacy?

A

Partial agonists have lower efficacy and cannot achieve the same maximal response as full agonists.

49
Q

What does intrinsic activity (IA) describe in drug-receptor interactions?

A

It describes the ability of a drug-receptor complex to elicit a maximum response relative to a full agonist.

50
Q

How can agonists differ in potency and efficacy?

A

Potency refers to the concentration needed to achieve a given response, while efficacy is the maximum response an agonist can produce.

51
Q

What is the main characteristic of antagonists regarding receptor activation?

A

Antagonists bind to receptors but do not activate them, preventing agonists from eliciting a response.

52
Q

How do competitive antagonists affect receptor activation?

A

They bind to the same site as the agonist, shifting the response curve, and higher antagonist concentrations require more agonist to achieve the same response.

53
Q

How do non-competitive antagonists affect receptor activation?

A

They bind to a different (non-agonist) site on the receptor and prevent activation, reducing the maximum possible response.

54
Q

How can agonists be used to classify receptors?

A

By measuring the potency of a range of agonists (selective agonism).

55
Q

How can antagonists be used to classify receptors?

A

By using competitive antagonists (selective antagonism).

56
Q

What are the two categories of cholinergic receptors?

A

Nicotinic (nAChR) and muscarinic (mAChR).

57
Q

What is the agonist, antagonist, and type for muscarinic receptors?

A

Agonist: Muscarine
Antagonist: Atropine
Receptor Type: mAChR (GPCR)

58
Q

What is the agonist, antagonist, and type for nicotinic receptors?

A

Agonist: Nicotine
Antagonist: Curare
Receptor Type: nAChR (Ion Channel)

59
Q

What concept does the classification of cholinergic receptors introduce?

A

The concept of receptor subtypes.

60
Q

What type of receptors are all histamine receptors?

A

GPCRs (G-protein-coupled receptors).

61
Q

What is the primary role of H1 receptors?

A

They are involved in allergic conditions.

62
Q

What is the primary role of H2 receptors?

A

They regulate gastric acid secretion.

63
Q

What conditions are H3 receptors associated with?

A

Central nervous system disorders such as narcolepsy and schizophrenia.

64
Q

What is the primary role of H4 receptors?

A

They are involved in immune responses and inflammatory conditions.

65
Q

what factors govern drug action

A
66
Q

what is affinity

A

Describes how well a ligand binds to the receptor
Affinity is a property shown by both agonists and antagonists

67
Q

efficacy

A

Describes how well a ligand activates the receptor

68
Q

affinity vs efficacy in agonists and antagonists

A
69
Q

What happens if receptors are inactivated?

A

The inactivation of receptors reduces the system’s ability to respond to agonists, leading to decreased physiological effects (e.g., relaxation).

70
Q

How does receptor number influence the response to an agonist?

A

A lower number of active receptors reduces the maximum possible response, even if the agonist concentration is high.

71
Q

What does a dose-response curve show in relation to receptor inactivation?

A

It illustrates the relationship between agonist concentration and the level of response, showing diminished response when receptors are inactivated.

72
Q

How is physiological relaxation affected by receptor activity?

A

Fewer active receptors result in less relaxation or other intended effects of the agonist.

73
Q

What happens when an irreversible antagonist binds to a receptor?

A

It permanently inactivates the receptor by binding in a way that it cannot be removed, preventing the receptor from responding to agonists.

74
Q

What is a receptor reserve?

A

A receptor reserve exists when only a small fraction of receptors need to be activated by a full agonist to produce the maximal system response.

75
Q

Does a receptor reserve exist for partial agonists?

A

No, partial agonists cannot produce a maximal response even when all receptors are occupied.

76
Q

What determines the size of a receptor reserve?

A

The size of the receptor reserve depends on the tissue and the agonist being used.

77
Q

What is signal transduction?

A

Signal transduction is the process where receptor activation triggers a series of steps, called a signalling cascade, leading to a cellular response.

78
Q

What is a signalling cascade?

A

A signalling cascade is a sequence of steps that transmits a signal from the receptor to produce a specific cellular response.

79
Q

What can activation of a receptor lead to?

A

It can lead to differing cellular responses, depending on the type of receptor and signalling pathway involved.

80
Q

What is allosteric modulation?

A

Allosteric modulation occurs when a molecule (allosteric ligand) binds to a site on the receptor separate from the active site (orthosteric site), influencing the receptor’s response.

81
Q

What is the difference between an orthosteric and an allosteric site?

A

The orthosteric site is where the agonist binds, while the allosteric site is where the allosteric ligand binds to modulate the receptor’s activity.

82
Q

How does an allosteric ligand affect receptor response?

A

It can either enhance or inhibit the receptor’s response to the agonist.

83
Q

What is inverse agonism?

A

Inverse agonism occurs when a drug binds to the same receptor as an agonist but produces the opposite pharmacological response.

84
Q

How does an inverse agonist differ from an antagonist?

A

An inverse agonist actively reduces receptor activity below its baseline, while an antagonist simply blocks the receptor without altering its baseline activity.

85
Q

What type of response does an inverse agonist induce?

A

It induces a response that counteracts the receptor’s natural activity or the effect of an agonist.

86
Q

What is tolerance in pharmacology?

A

Tolerance is a slow reduction in the effect of an agonist over time with continuous, repeated, or high-concentration exposure.

87
Q

What is desensitization in pharmacology?

A

Desensitization is a rapid loss of receptor response due to processes like uncoupling, internalization, or receptor degradation.

88
Q

How do tolerance and desensitization differ?

A

Tolerance develops slowly over time, while desensitization occurs rapidly.

89
Q

specific vs selectivity

A
90
Q

What type of agonist is isoprenaline?

A

Isoprenaline is a non-selective β-adrenoceptor agonist.

91
Q

Which receptors does isoprenaline target?

A

It targets both β₁-adrenoceptors (heart) and β₂-adrenoceptors (lungs).

92
Q

What is isoprenaline commonly used for?

A

It is used for conditions like bradycardia (slow heart rate) and heart block.

93
Q

What type of agonist is salbutamol?

A

Salbutamol is a selective β₂-adrenoceptor agonist.

94
Q

Which receptors does salbutamol primarily target?

A

It primarily targets β₂-adrenoceptors, which are found in the lungs.

95
Q

What is salbutamol used for?

A

It is used to open the airways in conditions like asthma and COPD.

pharmacology (7 decks)

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