signalling molecules Flashcards
what kinds of molecules to plasma membrane receptors accept?
hydrophilic molecules, small charged molecules like adrenaline and histamine or proteins like insulin and glucagon
what happens when a plasma membrane ligand binds?
the active receptor generates an intracellular chemical signal (second messenger)
how do intracellular signalling molecules act on cells?
they are bound to carrier proteins in the blood, then cross the plasma membrane and bind to a receptor in the cytosol which translocates to the nucleus and binds to the dna as a transcription factor
why is there specific and non specific binding in a binding assay?
because some ligands get stuck to the plastic well and not a receptor
why are high affinity ligands used in a binding assay?
to ensure ligand-receptor colllex stability for measurement
how is specific binding found in a binding assay?
total binding - non specific binding
what is measured in a competition assay?
inhibition of a known amount of bound high affinity ligand when a competitor is introduced
what does a curve further to the left on a competitive assay convey?
high affinity and ability to displace the known ligand at a low concentration
what does a curve further to the right on a competitive assay convey?
low affinity and displacement of the known ligand at a high concentration
how does the number of receptors bound correlate with physiological response?
maximal cellular response can occur with only some receptors being bound, increase in signal strength induces proportional increase in cell response
how does the number of surface receptors impact cell sensitivity to external signals?
high number requires less ligands to be present to induce a response and low number requires more ligands
how does the receptor affinity for ligands impact the cell sensitivity to external signals?
high affinity requires fewer ligands to produce a response and low affinity requires more ligands
how can the HER2 receptors promote cancer growth?
if HER2 is up regulated and a cell has too many the cell becomes hypersensitive to normal epithelial growth factor levels which wouldn’t normally stimulate growth and will undergo cell division which can stimulate cancer growth
how can affinity labelling be used as a method to track and recover cell receptors during purification for further study?
cells are incubated with a radioactive ligand and washed to remove excess ligand. the ligand-receptor complex is bound covalently and extracted from the cell membrane, however receptor-ligand binding ability is lost so further study cannot be done
how can affinity chromatography be used to recover receptors for further study?
beads in a column are covalently bonded to the ligand and a preparation of detergent solubilised membrane proteins is passed through the column, only binding the receptor, however these are very low abundance
