VF: Term 1 Week 4 ligands and drug targets

What is a receptor in pharmacology?

A cellular macromolecule that binds to a drug to initiate an effect.

What are the two main types of drug actions?

Receptor-mediated and non-receptor-mediated actions.

What is a ligand?

A molecule that binds to a receptor to produce a response.

What is the difference between endogenous and exogenous ligands?

Endogenous ligands occur naturally in the body (e.g., neurotransmitters, hormones), while exogenous ligands are drugs introduced externally.

What is the lock-and-key mechanism in drug-receptor binding?

A concept where a ligand (key) fits specifically into a receptor (lock) to initiate a response.

Name the four major types of receptors.

Ligand-gated ion channels, G-protein-coupled receptors (GPCRs), tyrosine kinase-linked receptors, and intracellular receptors.

Which type of receptor has the fastest response time?

Ligand-gated ion channels.

Which receptor type is the slowest in response?

Nuclear (intracellular) receptors.

What is an example of a ligand-gated ion channel?

Nicotinic acetylcholine receptor.

What is an example of a GPCR?

Beta-adrenergic receptor.

What is the main function of tyrosine kinase-linked receptors?

Mediating responses of growth factors like insulin and epidermal growth factor (EGF).

What type of ligands typically bind to intracellular receptors?

Highly lipid-soluble hormones such as steroid hormones.

What are the different types of bonds in drug-receptor interactions?

Ionic, hydrogen, Van der Waals, and covalent bonds.

Which type of bond is the strongest in drug-receptor interactions?

Covalent bond.

Which type of receptor is linked to second messengers like cAMP?

GPCRs.

Name a drug that targets voltage-gated sodium channels.

Local anesthetics.

What is the function of G-proteins in GPCR signaling?

They transduce signals from the receptor to intracellular effectors

Name one second messenger used in receptor signaling.

cAMP (cyclic adenosine monophosphate).

What is receptor upregulation?

An increase in receptor numbers due to long-term exposure to an antagonist.

What is receptor downregulation?

A decrease in receptor numbers due to prolonged agonist exposure.

What happens during receptor desensitization?

Reduced receptor response due to continuous agonist exposure.

What could cause reduced effectiveness of a beta-2 agonist used for asthma over time?

Receptor downregulation.

What is drug selectivity?

The ability of a drug to target a specific receptor or pathway.

What is drug specificity?

The extent to which a drug acts on only one type of receptor.

Give an example of a selective drug.

Heparin (acts as an anticoagulant).

Give an example of a non-selective drug.

Acepromazine (has multiple effects including sedation and hypotension).

What is drug efficacy?

The ability of a drug to produce a maximal response.

What does Emax represent?

The maximal response a drug can produce.

What is drug potency?

The amount of a drug needed to produce a specific effect.

What is EC50?

The concentration of a drug required to produce 50% of its maximal effect.

How is potency related to EC50?

A lower EC50 means higher potency.

What is the role of second messengers in cell signaling?

They amplify and relay signals from receptors to intracellular targets.

Name two common second messengers.

cAMP and Ca²⁺.

What enzyme converts ATP to cAMP?

Adenylyl cyclase.

What is the function of phospholipase C (PLC)?

It catalyzes the breakdown of PIP2 to DAG and IP3.

What does IP3 do in signaling pathways?

It increases intracellular calcium levels.

Name a drug target other than receptors.

Enzymes.

What is the target of non-steroidal anti-inflammatory drugs (NSAIDs)?

Cyclooxygenase (COX) enzymes.

What do ACE inhibitors target?

Angiotensin-converting enzyme (ACE).

What is the mechanism of action of proton pump inhibitors?

They inhibit the Na+/H+ pump.

Name a drug that targets nucleic acids.

Antineoplastic drugs (chemotherapy agents).

How do local anesthetics work?

They block voltage-gated sodium channels to prevent nerve signal transmission.

How do benzodiazepines exert their effect?

They enhance GABA action by acting on GABA-gated chloride channels.

What type of receptor does insulin act on?

Tyrosine kinase receptor.

How does atropine work?

It blocks muscarinic acetylcholine receptors.

How does digitalis (digoxin) affect the heart?

It inhibits Na+/K+ ATPase, increasing intracellular calcium.

What is the largest family of receptors?

GPCRs.

What is a competitive antagonist?

A drug that binds to the receptor but does not activate it, competing with the agonist.

What is an irreversible antagonist?

A drug that binds permanently to the receptor, preventing activation.

What is a partial agonist?

A drug that activates a receptor but produces a smaller response than a full agonist.