quiz 4 Flashcards
juxtacrine cell signaling
requires physical contact
paracrine cell signaling
on the local level
autocrine cell signaling
cell signals back to itself
endocrine cell signaling
cell signaling from a distance (signaling cell travels through circulatory system)
why does transduction of signal occur due to allosteric changes?
when a signal/ligand binds to its receptor, it changes its shape which changes its function
intracellular receptors
inside of cell, for small or nonpolar ligands that can diffuse across the cell membrane
membrane receptors
membrane-embedded receptors, for large or polar ligands that can’t enter the cell so their message is just relayed
steroid receptor mechanism
cortisol binds to intracellular cortisol receptor, causing it to change shape and release chaperone protein. without chaperone, receptor can now enter nucleus
how do acetylcholine receptors work (ligand-gated)?
Ach binds to receptor, allowing it to open and let Na+ ions flow in
protein kinase receptors
two pieces come together and phosphorylate themselves and/or other proteins
how does the insulin receptor (protein-kinase) work?
receptor binds insulin, causing it to change shape and form a dimer with another insulin receptor, leading to auto-phosphorylation. then it phosphorylates target proteins (insulin response substrates) which initiates cellular responses
GPCRs
ligand binds to GPCR, causing the receptor to change shape, assemble a GTP molecule, and activate a G protein. GTP binding subunit separates from G protein and binds to an effector protein, activating it which causes a change in cell function.
What happens when GTP is hydrolyzed to GDP
The G-protein is inactive again
mitogen
small molecule that induces a cell to begin cell division
second messengers
small non-protein molecules needed in some signal transduction pathways that relay signals from receptors on the cell surface to target molecules
why are second messengers needed?
they allow the cell to respond to a single event at the plasma membrane with many events within the cell (allows for diversification & amplification of cell responses)
what do map kinases do to each other?
they activate and phosphorylate the following enzyme/kinase (signal is amplified at each step)
what does mapk do?
enters the nucleus and promotes the expression of genes that allow the promotion of cell division
how do we get glucose needed for ATP
liver cells receive the signal epinephrine, indicating to stop storing glucose as glycogen, glycogen begins to break down to generate glucose, and glucose is released out of the cell into the blood
one molecule of epinephrine can trigger the release of ____ molecules of glucose
10,000
where does epinephrine bind on liver cell?
GPCR
after epinephrine binds to GPCR on liver cell, what does the activated G protein activate?
adenylyl cyclase (an effector protein)
what does adenylyl cyclase produce?
turns ATP into cAMP, cAMP then activates protein kinase A which inactivates glycogen synthase (preventing glucose from being stored as glycogen)
H zone
myosin only
I band
actin only
Z line
binds the actin
M band
binds the myosin
A band
myosin + actin overlap
