Antagonists in action Flashcards
Describe a receptor
Cellular protein that control chemical signalling between and within cells
Control Important physiological processes (sight, smell and taste)
Cellular targets of many drugs and some toxins
What is a receptor
Several binding sites
Bind ligands
Release ligand unchanged
membrane bound or free in cytosol
What are the 3 main receptor classes
Ligand-gated ion channel
G protein-coupled receptors (GPCR)
Receptor tyrosine kinase (RTK)
What are ligands
Specifically binds to receptor
Diverse chemical structure
What is the difference between endogenous and exogenous ligands
Endogenous - produced in body
Exogenous - drugs and toxins
Describe ligand binding to receptors
specifically binding
Affinity - how strongly a ligand binds to a receptor
Describe activation
Starts a chain of events via signal transduction
Describe inhibition
prevents activation by an agonist - antagonist
Signal transduction doesn’t occur
Describe efficacy in agonists
relative grading of responses that an agonist may have - High efficacy agonists can produce a maximal response even when low proportion of receptors
Lower efficacy may not be able to produce the small maximal response even when occupy entire receptor pop. - partial agonist
How is efficacy measured
measured by Emax in concentration-response curve
Partial lower than full agonist
Describe an inverse agonist
Constitutively active - ‘basal’ activity/signalling
inverse agonist - decrease in receptor activity by binding to receptors and reducing fraction of an active conformation - reducing signalling (negative efficacy)
Describe potency
Potency - measure of how much ligand it takes to produce a response
EC50 - measure potency of an agonist [produces 50% of its maximal response]
What is the most common type of antagonist
Competitive reversible antagonist - binds to receptor in reversible manner to compete directly with agonist binding - can overcome by increasing concentration of agonist
