Cell signaling Flashcards
T/F G proteins do not synthesize GTP from GDP + Pi
True
Signal transduction is initiated by the binding of ____ to receptor molecules in the plasma membrane.
Ligands.
T/F Multiple lipid-derived messengers are produced in membranes.
True
Why are phosphorylation cascades a common feature of cellular signal transduction?
They amplify signal many times.
T/F PLCs release soluble lipid second messengers in response to diverse inputs.
True
T/F Phospholipases D and A2 create other lipid second messengers.
True
What is the description of an agonist
Initiates signal activation
T/F All G proteins are enzymes.
True
G proteins bind to both GTP and GDP but not simultaneously. T/F
True
What is an autocrine signaling?
Self stimulation of growth.
PI3 Kinase synthesizes PIP3 to modulate cell shape and motility. T/F
True
Binding of a signaling molecule to a _____ leads directly to a change in distribution of ions across the membrane?
Receptor protein
G proteins are phospohorylated by GTP. T/F
False,
They are phosphorylated by GDP
ij
G alpha subunits bind to GTP
What is the function of a protein phosphatase?
Reverse Kinase action by removing a phosphate
G proteins change their shape when they release GDP and then bind to GTP. T/F
True
What are the steps occurring following binding of ligand to receptor tyrosine kinases?
Kinase activated —> Phosphorylation of tyrosine —-> phosphate activates signaling proteins
What is the source for cAMP?
Adenylyl cyclases synthesized from ATP.
Why are serine, threonine and tyrosine the only amino acids that can be phosphorylated by protein kinases?
Because they contain -OH group which can be replased w/ phosphate
What is paracrine signaling?
Signaling between neighboring cells.
Describe the mechanism of activation of heterotrimeric G proteins.
GDP is attached to a protein scaffold, when stimuli comes around GDP turns to GTP, beta and gama subunits leave. Alpha subunits attaches to adenyl cyclase which activates ATP to make cAMP, cAMP then activates Kinase.
GTP– GDP — Alpha + Adenyl cyclase – ATP — cAMP — Kinase activation.
Which amino acids can be phosphorylated by protein kinases?
Serine, threonine and tyrosine
The function of a protein phosphatase is to ____.
Remove phosphate and reverse kinase action
How does binding GTP control the activity of G proteins?
Activate protein.
Which signaling molecules stimulates a rise in cytosolic cAMP in animal cells?
Toxins, Theophylline, Caffeine, Adrenaline
Find examples of “positive feedback” in a cell.
output enhances original signal.
blood clots
What happens when a “G protein” Cleaves GTP to GDP?
Alpha and beta subunits are dissociated
Why does signaling through a peptide growth factor allow for more rapid responses in a cell than signaling through a steroid hormone such as estrogen?
Because it is bound to a membrane and has a scaffold.
Which signaling molecules stimulates a rise in cytosolic Ca 2+?
cAMP via PKA
What is the source for this Ca2+ (where is it stored)?
Endoplasmic reticulum.
Inositol triphosphate is a product of which enzymes?
Phopholipase (PLCs)
What makes adenylate cyclase a signaling protein?
Makes cAMP which triggers other responses.
List the secondary messangers
Ca 2+, IP3, cAMP
The mitogen-activated protein kinases are among the most commonly used proteins kinases in cells. They are often employed by the cell in protein kinase cascades, where MAP3K phophorylates and activates MAP2K, which in turn phosphorylates MAPK. What are the possible advantages for the cell to employ a protein kinase cascade?
Cell proliferation
Differentiation
Cell survival.
