Second messengers Flashcards
Gq activates
PLCB
PLCB acts on/cleaves
PIP2
The products of the cleavage of PIP2 by PLCB are second messengers:
IP3 and DAG
DAG is
Lipophilic
Dag remains
in the membrane
IP3 is
Hydrophilic
IP3 diffuses to
the cytosol
IP3 is water….
water soluble
Where does IP3 go?
diffuses to the cytosol and then to the ER
What does IP3 bind to?
IP3-gated Ca 2+ release channels in the ER
Ca2+ stored in the ER does what?
Ca2+ stored in the ER is released when the channels open and raises the concentration in the cytosol
DAG stays in
the plasma membrane
DAG with Ca2+ and phosphatidylserine activate
PKC-protein kinase C
PKC then….
phosphorylates target proteins
DAG can also be….
DAG can also be cleaved to release arachidonic acid
Extracellular calcium
The principal mineral in bone
Intracellular calcium is part of the
second messenger system
What stimuli activates channels in the plasma membrane?
Extracellular stimuli
What stimuli activates Ca2+ channels in the ER and SR membrane?
Intracellular stimuli (GPCR mediates IP3 receptor)(ryanodine receptor)
What terminates Ca 2+ signal?
- calcium pumps
- Ca 2+ transporters
Calcium pumps are..
calcium pumps use the energy of ATP hydrolysis to pump Ca 2+ out of the cytosol
Ca transporters are..
Ca transporters couple the efflux of Ca2+ to the influx of Na+ in muscle and nerve cells
What helps relay calcium’s signal in the cytosol?
Ca binding proteins like Calmodulin
The effects of calcium are indirect and mediated by what?
protein kinases: CaM-kinases: Ca/Calmodulin-dependent kinases
effects of calcium are mediated by
CaM-Kinase II- a protein kinase that autophosphorylates (positive feedback)
