W1: Hormone-Receptor Interaction & Signalling Mechanisms Flashcards
intracellular vs intercellular signalling
com w/in a cell
com btwn diff cells (I.e. extracellular signalling) -
Endocrine, autocrine, paracrine, neuroendocrine, NT
ligand (key)
any molecule that binds to a specific site on a protein or other molecule e.g. hormone that binds to a receptor
receptor (lock)
a molecule that recognises & binds to a ligand w/ high specificity
affinity
Some hormones can bind to multiple diff receptors, but w/ diff affinities
Some ligands don’t fit exactly into the receptor, but do work w/ a bit of adjustment
what molecules can a ligand be?
protein, lipid or carbohydrate
ligands - agonist vs antagonist
molecules that bind to a receptor & trigger a signalling pathway
molecules that bind to a receptor but do NOT trigger signalling (block the signal)
ligands - precursor form
e.g pro-hormones
ligands - binding partner
if ligand not soluble in blood, needs something to carry it around blood system
characteristics of protein & peptide hormones
Small or large
Often pro-hormone (prod as AA chain, then processed)
Hydrophilic
Soluble (free) in blood, so shorter half-life (bc don’t always need carrier protein, so get degraded faster)
Degraded by proteolytic enzymes
Extracellular receptor (bc ligand can’t easily cross cell mem)
Stored & rapid release (bc can’t get out of cell easily, able to make it inside cell then store it)
characteristics of steroid hormones
Small
Hydrophobic
Bound to plasma proteins, so longer half-life (protected from degradation)
Intracellular receptor (bc ligand can cross mem)
Synthesised on demand (bc tricky to store inside, as they’re able to cross plasma mem)
Excreted (thru urinary system)
characteristics of thyroxine
Small, potent
Hydrophobic
Bound to plasma proteins
Intracellular receptor
Stored in thyroid by binding partner (has BP inside cell, so able to build up amount before releasing)
characteristics of epinephrine
Small, potent
Hydrophilic
Soluble (free) in blood
Degraded
Extracellular receptor
Stored in adrenal medulla
receptors
Proteins
Molecular switches
Trigger cellular mechanism
Extracellular or intracellular
Specificity - accuracy
Affinity - strength, higher affinity constant (Ka) = stronger
Avidity = total strength (sometimes ligands bind at multiple places on receptor, so multiple interactions, so helpful to work out total strength)
types of intracellular receptors
Some receptors are cytoplasmic (e.g. cortisol, oestradiol, testosterone, progesterone)
Some are nuclear (e.g. thyroid hormones) (affect gene reg, so take longer to have an effect)
how does extracellular signalling work?
Signalling cascades ‘amplify’ the original signal (i.e. highly sensitive to hormone - often potent) (can also include gene reg)
