cell communication Flashcards
autocrine signal
a cell targets itself; signal affects the cell secreting it
signaling across gap junctions
a cell targets a cell connected by gap junctions
paracrine signalling
a cell targets nearby cell
example of paracrine signaling
synapse: paracrine signal causes neurotransmitter secretion
endocrine signalling
a cell targets a distant cell through the bloodstream
steps of responding to a signal
reception
transduction
response
reception: signal molecules bind to
receptors; receptor does not move signal molecule, only connects to it
signals are ligands, what is a ligand?
small molecules that bind to larger molecules
membrane receptors location
-Partly inside and outside the membrane, making it a connection point between outside and inside of the cell.
-They detect signals outside the cell and make signals inside the cell
(Hydrophilic signals cannot pass through membrane)
categories of membrane receptors
G protein coupled
Receptor tyrosine kinases
Ion channel
G protein coupled receptors have multiple
transmembrane regions
G protein coupled receptors have an internal or external site for signal molecules?
external
G protein coupled receptors have an internal connection to
G protein
how are G protein coupled receptors activated?
by attaching GTP so that it can activate 1 cell process
receptor tyrosine kinases energizes something by…
giving it ATP
kinase:
transfer phosphate from ATP to give energy to another molecule to activate things
how many tyrosine amino acids in receptor tyrosine kinases?
6 tyrosine amino acids, each can hold phosphate to form ATP
ion channels:
channel that ions can pass through
in ion channels, ions must move…
down concentration gradient
intracellular receptors
found INSIDE cell (often in nucleus) and detects signals that can pass through cell membrane
transduction definition
converting info from one form to another
pathway:
series of interactions that accomplish something
-Each triggers the next like falling dominoes
phosphorylation
take phosphate off ATP and give it to something
phosphorylation cascades:
pathway of enzymes, and each adds phosphate to the next
dephosphorylation
removes a phosphate group, deactivates enzyme, turns off pathways
dephosphorylation is accomplished by
protein phosphatases
where can response to a signal occur?
in cytoplasm (turns enzyme pathways on or off) or in the nucleus (turns genes on or off)
response regulation: control mechanisms
signal amplification, different responses in different cells, pathway optimization, ending signal
signal amplification:
*phosphorylation often occurs in cascades, where each step can activate multiple molecules of the next step.
*Small amount of signal can cause a large response, so you can control length of cascade to control signal.
different responses in different cells:
*Receptor can be connected to different pathways
*Pathways determines cell behavior change
*Cells respond differently to same signal
pathway optimization
*Pathway efficiency is determined by how close to each other steps are (where is B relative to A?)
if proteins for each step are far apart, pathway is _____.
slower
scaffolding proteins:
position pathway components in proper order to maximize pathway efficiency (holds protein A next to protein B)
ending signal
Cell signal pathways must be inactivated when no longer needed
when external signal becomes weak…
pathways are turned off
apoptosis:
controlled cell suicide
possible reasons for apoptosis:
-Cells only needed during one portion of development
-Cell damage
-Infected cells
-Cells no longer function properly
