Pharmacodynamics: Molecular Mechanisms of Drug Action
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Questions and Answers

What is the relationship between agonist concentration and receptor occupancy?

  • The relationship is inverse, but only at high concentrations
  • Increased agonist concentration increases receptor occupancy (correct)
  • Increased agonist concentration decreases receptor occupancy
  • There is no correlation between agonist concentration and receptor occupancy

    • Surmountable and insurmountable receptor antagonism are the same.

    False

    What is pharmacology?

    Pharmacology is the study of how drugs act.

    A receptor is a ______________________ molecule that binds to a specific drug or ligand.

    <p>protein</p> Signup and view all the answers

    Match the following terms with their definitions:

    <p>Agonism = The binding of a drug to a receptor, resulting in a response. Partial Agonism = The binding of a drug to a receptor, resulting in a partial response. Antagonism = The binding of a drug to a receptor, blocking the response. Affinity = The ability of a drug to bind to a receptor. Efficacy = The ability of a drug to produce a response.</p> Signup and view all the answers

    What is the relationship between agonist concentration and response?

    <p>The response increases with agonist concentration until a maximum is reached</p> Signup and view all the answers

    What is the primary function of receptors in cells?

    <p>To initiate a change in cell function</p> Signup and view all the answers

    Receptors are found only on the surface of cardiac cells.

    <p>False</p> Signup and view all the answers

    What is the name of the receptor that responds to noradrenaline?

    <p>a-adrenoceptor</p> Signup and view all the answers

    Different cell types have different ______________ of receptor profiles.

    <p>densities</p> Signup and view all the answers

    Match the following receptors with their corresponding chemical agents:

    <p>Muscarinic acetylcholine receptors = Acetylcholine b-adrenoceptors = Adrenaline a-adrenoceptors = Noradrenaline</p> Signup and view all the answers

    What is the role of transporters or carrier molecules in cells?

    <p>To transport ions and small organic molecules across cell membranes</p> Signup and view all the answers

    What is pharmacokinetics concerned with?

    <p>what the body does to a drug</p> Signup and view all the answers

    Paul Ehrlich was awarded the Nobel Prize in 1954.

    <p>False</p> Signup and view all the answers

    What is the fundamental concept in drug action indicated by Paul Ehrlich?

    <p>A drug will not work unless it is bound.</p> Signup and view all the answers

    Drugs can exert their effects by binding to _________ targets.

    <p>protein</p> Signup and view all the answers

    Match the following terms with their descriptions:

    <p>Receptors = Ion channels</p> Signup and view all the answers

    What is the function of agonists in the body?

    <p>To mimic the actions of endogenous ligands</p> Signup and view all the answers

    Receptors show absolute ligand selectivity.

    <p>False</p> Signup and view all the answers

    What is the term for the ability of a drug to bind to specific receptors in the body?

    <p>Selectivity</p> Signup and view all the answers

    Drugs that bind to and activate receptors are called ______________________.

    <p>agonists</p> Signup and view all the answers

    Match the following drugs with their primary effects:

    <p>Phenylephrine = relieves nasal congestion Diphenhydramine = decongestant and dry mouth Paracetamol = pain relief</p> Signup and view all the answers

    What is the result of increasing the dose of a drug that acts on multiple receptors?

    <p>Adverse effects</p> Signup and view all the answers

    Agonist binding to receptors is usually irreversible.

    <p>False</p> Signup and view all the answers

    What is the term for the strength of attraction between an agonist and a receptor?

    <p>Affinity</p> Signup and view all the answers

    The binding of an agonist to a receptor requires intermolecular forces such as ______________________ and hydrogen bonding.

    <p>van der Waals forces</p> Signup and view all the answers

    What are the 4 major types or superfamilies of receptors?

    <ol> <li>Ion channel receptors, 2. G protein-coupled receptors, 3. Enzyme-linked receptors, 4. Nuclear receptors</li> </ol> Signup and view all the answers

    Where are ion channel receptors located?

    <p>Cell membrane</p> Signup and view all the answers

    Enzyme-linked receptors respond to fast neurotransmitters.

    <p>False</p> Signup and view all the answers

    Ions __ cross the cell membrane when the ion channel is closed.

    <p>cannot</p> Signup and view all the answers

    Match the receptor superfamilies with their respective effector proteins:

    <p>Ion channel receptors = Channel G protein-coupled receptors = Enzyme or channel Enzyme-linked receptors = Enzyme Nuclear receptors = Gene transcription</p> Signup and view all the answers

    Study Notes

    Pharmacodynamics: Molecular Mechanisms of Drug Action

    • Pharmacodynamics is the study of the effects of drugs on the function of living systems.
    • It involves the interaction between a drug and components of the organism.

    Drug Action

    • Most drugs exert their effects by binding to protein targets such as receptors, ion channels, enzymes, and transporters.
    • A drug must bind to a target to produce an effect.

    Receptors

    • Receptors are proteins that allow a chemical agent (drugs, hormones, neurotransmitters) to initiate a change in cell function.
    • Receptors are the cell's 'sensing elements' and provide molecular communication between the chemical agent and the transduction process.
    • Different cell types have different receptor profiles, which determines the hormones and neurotransmitters to which the cell responds.

    Agonists and Antagonists

    • Agonists mimic the actions of endogenous ligands and bind to the receptor to produce a response.
    • Antagonists block the actions of endogenous ligands and bind to the receptor to prevent a response.

    Ligand Selectivity

    • Receptors show ligand selectivity, meaning each receptor type is activated by a small number of substances.
    • Receptor activation requires a good 3-D "fit" between the agonist and receptor.

    Selectivity of Drugs

    • Useful drugs show selectivity, binding only to certain receptors to produce a specific response.
    • Selectivity is reciprocal, meaning each drug only binds to certain receptors and each receptor recognises only certain drugs.

    Limitations of Selectivity

    • Selectivity is not absolute, as most drugs act on more than one receptor.
    • Increasing the dose of a drug can activate other receptors, leading to adverse effects.

    Drug-Induced Responses

    • Drugs act by binding to specific drug targets, such as receptors, to produce a response.
    • Agonist binding requires intermolecular forces between the agonist and receptor and is usually reversible.
    • The strength of agonist binding is determined by the forward and backward rate constants.

    Receptors and Other Drug Targets

    • A drug will not work unless it is bound to a protein target, such as receptors, ion channels, enzymes, or transporters.
    • Receptors are sub-divided into 4 major types or superfamilies: ion channel receptors, G protein-coupled receptors, enzyme-linked receptors, and nuclear receptors.

    Ion Channel Receptors

    • Located in the cell membrane
    • Collection of proteins form a central pore/channel
    • Ions cannot cross the cell membrane without binding of an agonist
    • Examples: nicotinic acetylcholine receptor
    • Characteristics:
      • Mechanism of signal transduction: binding of an agonist alters ion channel structure, allowing ions to flow into the cell
      • Receptor location: cell membrane
      • Effector protein: channel
      • Time scale of action: milliseconds, very fast
      • Agonist: ACh (acetylcholine)
      • Antagonist: pancuronium (used to produce paralysis during anaesthesia)

    G Protein-Coupled Receptors

    • Also located in the cell membrane
    • 7 transmembrane domains
    • Examples: adrenoceptors, muscarinic acetylcholine receptors
    • Characteristics:
      • Mechanism of signal transduction: binding of an agonist activates a G protein, which in turn activates an effector protein
      • Receptor location: cell membrane
      • Effector protein: enzyme or channel
      • Time scale of action: seconds, fast
      • Agonist: salbutamol (relieves bronchospasm in asthma)
      • G proteins link GPCRs to effector proteins that generate intracellular second messengers

    Enzyme-Linked Receptors

    • Also located in the cell membrane
    • Examples: insulin receptor, receptors for cytokines, growth factors
    • Characteristics:
      • Mechanism of signal transduction: binding of an agonist activates a linked enzyme
      • Receptor location: cell membrane
      • Effector protein: enzyme (e.g. kinase)
      • Time scale of action: minutes, slow
      • Agonist: insulin (used to reduce blood glucose levels)

    Nuclear Receptors

    • Located in the intracellular compartment
    • Examples: glucocorticoid receptor, other steroid hormone receptors
    • Characteristics:
      • Mechanism of signal transduction: binding of an agonist activates gene transcription
      • Receptor location: intracellular
      • Effector protein: gene transcription
      • Time scale of action: hours, very slow
      • Agonist: glucocorticoid (prednisolone, an anti-inflammatory agent)

    Protein Targets for Drug Action

    • Receptors: agonists bind to and activate receptors, while antagonists bind to but do not activate receptors
    • Ion channels: blockers physically plug the ion channel, while modulators bind to accessory sites and modulate channel activity
    • Enzymes: substrate analogues competitively inhibit the enzyme, while some drugs act as false substrates for enzymes
    • Transporters: specific carrier proteins transport ions and small organic molecules across cell membranes, and some drugs inhibit transporters or act as false substrates.

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    Related Documents

    Foundations of Pharmacology PHAR2210 Introduction to Drug Action PDF
    Receptors and Drug Channels PDF

    Description

    This quiz covers the effects of drugs on living systems, including drug-target interactions and protein binding.

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