Cell to cell communication: Receptors and pharmocology Flashcards
What are ligands?
-a substance that forms a complex with a receptor which will directly or indirectly affect a cellular activity
-drugs or chemicals
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What are ligand gated ion channels?
ionotropic receptors i.e. neurotransmitter: nicotinic acetylcholine receptors
a group of transmembrane ion-channel proteins which open to allow ions such as Na⁺, K⁺, Ca²⁺, and/or Cl⁻ to pass through the membrane in response to the binding of a chemical messenger (i.e. a ligand), such as a neurotransmitter.
What are receptors with intrinsic enzymatic activity?
- receptor tyrosine kinases
- upon receptor activation they can perform enzymatic reactions- phosphorylation- on themselves and other proteins
- hormone insulin receptor
What are intracellular/ nuclear receptors?
receptors inside the cell or in the nucleus
receptors for steroid (testosterone
thyroid hormone and vitamin D)
What are G protein- coupled receptors?
- 7 transmembrane domain receptor
- receptor for hormones: glucagon, neurotransmitter: muscarinic ACh receptors extracellular nucleotides (ATP): P2Y
How to measure the action of a drug/ligand?
use increasing drug concentrations and record the corresponding induced response amplitude to determine the effective range of drug concentrations
What is EC50?
effective concentration of ligand producing 50% of Emax maximal response
What is potency?
a measure of drug activity expressed in terms of the amount of drug required to produce an effect of given intensity (50% of Emax)
-the drug dose that causes 50% of the maximum effect.
What is affinity?
defined as a drug’s ability to bind to a receptor
it indicates how tight he bond between a ligand and receptor is
What does potency depend on?
affinity
number of receptors available for binding
How can affinity be determined?
can be determined by measuring the proportions of receptors-ligand complexes formed compared to the total number of receptors at different ligand concentrations
What is Bmax?
maximum binding has occurred and all receptors are occupied
What is Kd?
affinity of the ligand for its receptor lower Kd means less drug is used to saturate 50% of its receptors
Need a lower concentration to bind 50% of the receptors
What is Efficacy?
the ability of the ligand, following its binding to the receptor, to induce a biological response via the receptor activation: magnitude of this response
What is an agonist?
affinity for its receptor and causes its activation upon binding leading to a response
induces a response which is concentration dependant
