Sensing and reacting to extracellular conditions Flashcards
Why do we need to sense and react
cells in ac and plants can respond to hormonal and other signals to maintain homeostasis
Where are receptors located
- cell surface
- inside the cell
Three types of transmembrane receptors in eukaryotes
- protein kinases
- ion channel receptors
- G protein linked receptors
what do protein kinase receptors do
catalyse phosphorylation of themselves and/or other proteins
What do insulin receptors do and initiate
phosphorylates itself and other insulin response substrates
- this initiates insertion of glucose transporters into the plasma membrane
What are ion channel receptors
channel proteins that allow ions to enter or leave a cell
What are G protein linked receptors
Ligand binding changes the shape of the cytoplasmic region which bind to G proteins
What are G proteins
Mobile membra.ne proteins with three subunits
What do G proteins bind to
GDP and GTP
Basic biological circuit
Receptors - Signal transduction - Biological response
GTP is hydrolysed into what in G protein receptors
GDP
What does binding to the G protein receptor do
activates the effector which causes a change in cell function
Activation of an effector by a G protein
Adrenaline binds to G rec in heart muscle; this activates an enzyme to produce cyclin AMP (cAMP)
Inhibition of an effector by a G protein
can be inhibited by adrenaline as well
- the enzyme that produces cAMP is inhibited
What does direct signal transduction result from
from the action of the receptor itself on effector proteins
