CELLS - cell-cell interactions

what are the three types of cell junctions?

tight junctions, desmosomes, gap junctions

tight junctions

watertight seal, nothing can get through space between cells
ex: bladder, intestines

desmosomes

ions and small molecules like what can get through, cells anchored to each other via attachments at each others cytoskeleton
ex: skin, intestines

gap junctions

like a tunnel between cells to pass water and ions
ex: neurons, cardiac muscle

membrane receptor protein type

integral protein that binds a specific ligand

general process of membrane receptors

ligand binds, conformational change, intracellular signal transduction

what are the 3 main types of membrane receptors?

ligand gated ion channel, GPCR, enzyme linked receptors

ligand gated ion channels

transmembrane ion channels bind a ligand allosterically and the channel opens or closes, common in neurons, rare for ligand binding to happen intracellular

g protein components

alpha, beta, gamma subunits; beta and gamma associated; gtp/gdp binds the alpha subunit; alpha and beta subunits attached to membrane via lipid anchors

g protein coupled receptors

only euks, largest class, most drug targets, stim or inhib activity, 7 transmembrane alpha helixies

what type of gprot is associated with GPCRs?

heterotrimeric

GPCR signal transduction

1. ligand binds
2. conformational change
3. GDP on alpha exchanges for a GTP to become active
4. alpha dissociates and regulates other prot
5. target protein relay signal via second messenger as long as ligand is bound
6. return to normal when GTP becomes GDP

what are the 2 domains of an enzymes linked receptors?

ligand binding - extracellular; enzymatic domain - intracellular

receptor tyrosine kinases

enzyme linked membrane receptors that attach phosphates to tyrosines, often associated with growth factors and hormones, occur in pairs