Lecture 14: Signal Transduction Part I Flashcards
What is signal transduction?
Process by which extracellular signal are communicated to specific parts of cell.
What 3 steps are required for signaling?
signal, receptor, target molecule
Signal transduction pathways not only communicate signals but _________ them as well.
amplify
Signal amplification across several steps in a cascade is __________.
exponential
Signal—receptor—________—Target molecule 1—2nd messenger—__________
1st messenger, downstream target (nucleus)
What are some extracellular signaling molecules?
Neurotransmitters, peptides, endocannabinoids
What are some cell-impermeant molecules?
Most neurotransmitters
What are some cell-permeant molecules?
Cholesterol derived hormones
What are some cell associated molecules?
cell-cell adhesion molecules
GCPRs are ________ receptors
metabotropic
Heterotrimeric (large) g-proteins are composed of how many subunits?
3, (alpha, beta, gamma)
the _______ subunit binds either to guanosine triphosphate (GTP) or guanosine diphosphate (GDP)
alpha
G proteins function as molecular __________.
switches (They are “on” when they bind GTP, they are “off” when they bind GDP.)
3 classes of G-alpha subunits are…?
GsA: stimulatory
GiA: inhibitory
GqA
Gα subunit will eventually hydrolyze the attached __________ through its own enzymatic activity, allowing it to re-associate with Gβγ to form the “resting” G-protein. ____________ accelerate the hydrolisis of GTP to GDP. This way they regulate the activity of G-proteins and terminate the signal. The effector (e.g. adenylyl cyclase) itself may possess intrinsic GAP activity, which helps deactivate the pathway.
GTP to GDP, GTPase-activation proteins (GAPs)
