Chapter 16 - Cell Signaling (exam 4)
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76 Terms
cells communicate through a large variety of…
extracellular signals
cells must interpret signals from other cells to help…
coordinate their behaviors
information can come in a variety of forms, so cellular communication involves…
converting those signals from one form to another
what is signal transduction?
the process of converting an extracellular signal into an intracellular signal to elicit a cellular response
describe a typical communication between cells
the signaling cell produces a signal molecule that is detected by a target cell
what do target cells have and what do they do?
receptor proteins
recognize and respond to the signal molecule
when does signal transduction begin?
when the receptor protein on the target cell receives an incoming extracellular signal and converts it to an intracellular signal
extracellular signal molecules…
stimulate a target cell by binding to its receptor proteins (could be intracellular or cell-surface receptors)
extracellular signals can occur…
slowly or rapidly
cell signals can act over what ranges?
long or short
what are two examples of long-range signals and communication?
endocrine and synaptic/neuronal
what are two examples of short-range signals and communication?
paracrine and contact-dependent
endocrine signals
hormones are carried in the blood to distant target cells
synaptic/neuronal signals
transmitted along axons to remote target cells
paracrine signals
signals released by cells into extracellular fluid and act locally
contact-dependent signals
direct communication through cell-cell contact
endocrine signals can be described as…
a “public” style of communication
with endocrine cells, the signal is broadcasted…
throughout the whole body through secretion in the bloodstream
cells that produce hormones are called…
endocrine cells
when do electrical signals get converted into chemical signals in neuronal cells?
when action potentials reach the axon terminal
chemical signals in neuronal cells are in the form of…
neurotransmitters
paracrine signals remain in…
the vicinity of the cell that secretes them (short range)
paracrine signals act as…
a “local mediator”
autocrine signaling may be used with cancer cells to…
promote their survival
autocrine signaling
local mediators that are produced by the cells themselves to promote survival or proliferation
with a contact-dependent signal, how does the cell make physical contact?
a membrane bound signaling molecule in the signaling cell and a receptor protein embedded in the plasma membrane of the target cell
the notch receptor is a…
transcription regulator
what membrane-bound signal protein binds to notch?
Delta
what happens when the Delta signal protein on one cell binds to its receptor, Notch, on a neighboring cell?
the receptor is cleaved
what happens to the released part of Notch?
the cytosolic tail of Notch migrates to the nucleus
in the nucleus, what does the cytosolic tail of Notch do?
it activates Notch-responsive genes (like genes that control nerve cell production in fruit flies)
cells of a multicellular organism are exposed to how many signals in its environment?
hundreds
what determines if a cell responds to a signal?
if that cell possesses a receptor protein for that signal
receptors can be…
cell surface receptors or intracellular receptors
what two categories do extracellular signals fall into?
those that are too large or too hydrophilic to cross the plasma membrane
those that are small enough or hydrophobic enough to diffuse across the plasma membrane
large and hydrophilic molecules typically bind to…
cell-surface receptors/membrane receptors (same things, two names)
small and hydrophobic molecules typically bind to…
intracellular enzymes or intracellular receptor proteins
how do cell surface receptors relay extracellular signals?
via intracellular signaling pathways
describe the first signal transduction step by receptor proteins
binds the primary messenger and generates new secondary messengers
signals get passed from one intracellular signaling molecule to the next in what fashion?
downstream
signals get passed downstream from one intracellular signaling molecule to the next until…
the response has been completed
cell surface receptors relay…
extracellular signals
what are the crucial functions that intracellular signaling pathways perform?
relay the signal onward
amplify the signal received
receive signals from multiple intracellular pathways and integrate them
distribute the signal to more than one signaling pathway or effector protein
intracellular signaling proteins can act as…
molecular switches
molecular switches function to allow signals to switch between…
inactive and active states
once proteins are activated, what can they do?
these proteins can turn on other proteins in the signaling pathway
proteins persist in the active site until…
another switch turns them off
what are some proteins that act as molecular switches…
kinases and GTP-binding proteins
list the two types of kinases
serine/threonine kinases
tyrosine kinases
what are the three classes of cell-surface receptors?
ion-channel-coupled receptors
G-protein-coupled receptors (GPCRs)
enzyme-coupled receptors
ion-channel-coupled receptors
allow the flow of ions across a plasma membrane
what changes to ion-channel coupled receptors result in?
changes in the membrane potential and produce an electrical current
what do G-protein-coupled receptors activate?
activates membrane-bound, trimeric GTP-binding proteins (G proteins)
G-proteins
activate either an enzyme or an ion channel in the plasma membrane
G-protein-coupled receptors are composed of…
a single polypeptide chain that is a seven-pass transmembrane receptor protein
a signal protein for G-protein coupled receptors binds to…
an inactive receptor
once the signal molecule binds to the inactive receptor protein, what happens?
the proteins undergoes a conformational change that enables it to activate a G protein on the underside of the plasma membrane
each variety of G protein is specific…
for a set of receptors and target enzymes or ion channels
each G protein contains what subunits?
alpha, beta and gamma subunits
how are gamma and alpha subunits attached to the plasma membrane?
short lipid tails
when the G protein is in its unstimulated (inactive) state, that means…
that the alpha subunit has GDP bound and the G protein is idle (without purpose or effect)
when the signal molecule (extracellular ligand) binds to the receptor…
this activates the G protein, and causes the alpha subunit to release GDP and exchange it for GTP
enzyme-coupled receptors
transmembrane proteins that display their ligand-binding domains on the outer surface of the plasma membrane
what does the cytoplasmic domain of the receptor do?
either acts as an enzyme itself or forms a complex with another protein that acts as an enzyme
what do enzyme coupled receptors do?
they respond to growth factors and regulate cell growth, proliferation, differentiation, and survival
enzyme-coupled receptors mediate and direct…
the rapid reconfigurations of the cytoskeleton to control cell shape and movement
enzyme-coupled receptors are inactive when…
they are apart
enzyme-coupled receptors can be activated by…
a signal molecule in the form of a dimer
just a plain signal molecule
what does the activation of a receptor tyrosine kinase (RTK) do?
stimulates the assembly of an intracellular signaling complex
receptor tyrosine kinases (RTKs)
large class of enzyme-coupled receptors
the main domain of RTKs is located in…
the cytosol
what does the cytoplasmic domain of RTKs do?
phosphorylates specific tyrosines on selected intracellular proteins
when the signal molecule (in the form of a dimer) binds to the inactive RTKs…
the 2 receptors dimerize
what does dimerization of RTKs cause?
the activation of the kinases, which enables them to phosphorylate their tyrosines
each phosphorylated tyrosine…
serves as a specific binding site for different intracellular signaling protein
the intracellular signaling protein…
relays the signal to the cell’s interior