Examples of cellular responses to signals Flashcards
what is an important part of cell-to-cell communication?
the release of signal molecules
how are water soluble molecules released?
released from vesicles via regulated exocytosis
how are lipid soluble molecules released?
released by diffusion as soon as they are synthesized
what happens in the golgi body?
vesicles are generated by the Golgi and tagged to specific destinations
these include the cell surface where they release their contents by exocytosis
what is constitutive regulation?
extracellular matrix materials
what are regulated regulations?
signals (paracrine, endocrine and neuronal)
what in the function of vessicle associated proteins?
-building the vesicle
-loading of signal molecules into the vesicle
-guiding the vesicle to the correct location
-regulating exocytosis
-vesicle recovery after exocytosis
how do SNARES and Rabs work?
interact with each other to bring the vesicle into the right place.
They also twist together to keep the vesicle in place
what happens when the vesicle gets to the correct site?
exocytosis
what proteins are involved in getting the vesicle to the correct place?
SNARES and Rabs
what is synaptotagmin?
protein involved in exocytosis of vesicles
- makes exocytosis Ca2+ dependent
how does synaptotagmin make exocytosis Ca2+ dependent?
Ca2+ binding to synaptotagmin changes its shape bringing the vesicle towards the cell membrane
thus for regulated exocytosis to occur a cell must increase its Ca2+ concentration at the site of release
where are adrenal chromaffin cells found?
within the adrenal medulla
what is the function of adrenal chromaffin cells?
releases catecholamines (adrenaline and noradrenaline) in response to stress
what stimulates the secretion of catecholamines from adrenal chromaffin cells?
secretion is stimulated by acetylcholine release from nerve
how does acetylcholine stimulate adrenal chromaffin cells?
-activates nicotine acetylcholine receptor
-the receptor channel opens and Na+ influxes
-cell depolarizes and opens voltage-gated Ca2+ channels
-Ca2+ influx also causes exocytosis
-Ca2+ can also stimulate tyrosine hydroxylase (TH) to make replacement catecholamines
where are beta cells of the pancreas found?
found within the islets of Langerhans
what is the function of pancreatic beta cells?
release insulin in response to increased glucose concentration in the blood
how are beta cells signalled to produce insulin?
-glucose is transported into the beta-cell
-then metabolized to form ATP
-ATP acts to close a K+ channel
-more +ve charge within the cell causes it to depolarize
-opens voltage-gated Ca2+ channels
-Ca2+ enters the cell
-stimulates exocytotic release of insulin
-also increases insulin synthesis
-insulin acts on insulin receptors to remove glucose from the blood into cells
what are mast cells?
cells of the immune system found within connective tissue
what is the structure of mast cells?
contain multiple granules (vesicles)
what is mast cell degranulation?
Massive exocytosis called degranulation
what is the function of mast cells?
-release a cocktail of biologically active molecules
-provide first-line of defense to foreign antigens, tissue damage and pathogens
how are mast cells signaled to undergo degranulation?
-allergens cross-link two IgE (FcR1) receptors
-trigger a pathway that releases Ca2+ from the endoplasmic reticulum
-increased Ca2+ causes degranulation
-receptor activation also activates other intracellular pathways that increases production of more cytokines
