apoptosis
programmed cell death
autocrine signal
signal that is sent and received by the same or similar nearby cells
autoinducer
signaling molecule secreted by bacteria to communicate with other bacteria of its kind and others
cell-surface receptor
cell-surface protein that transmits a signal from the exterior of the cell to the interior, even though the ligand does not enter the cell
chemical synapse
small space between axon terminals and dendrites of nerve cells where neurotransmitters function
cyclic AMP (cAMP)
second messenger that is derived from ATP
cyclic AMP-dependent kinase
(also, protein kinase A, or PKA) kinase that is activated by binding to cAMP
diacylglycerol (DAG)
cleavage product of PIP2 that is used for signaling within the plasma membrane
dimer
chemical compound formed when two molecules join together
dimerization
(of receptor proteins) interaction of two receptor proteins to form a functional complex called a dimer
endocrine cell
cell that releases ligands involved in endocrine signaling (hormones)
endocrine signal
long-distance signal that is delivered by ligands (hormones) traveling through an organism's circulatory system from the signaling cell to the target cell
enzyme-linked receptor
cell-surface receptor with intracellular domains that are associated with membrane-bound enzymes
extracellular domain
region of a cell-surface receptor that is located on the cell surface
G-protein-linked receptor
cell-surface receptor that activates membrane-bound G-proteins to transmit a signal from the receptor to nearby membrane components
growth factor
ligand that binds to cell-surface receptors and stimulates cell growth
inhibitor
molecule that binds to a protein (usually an enzyme) and keeps it from functioning
inositol phospholipid
lipid present at small concentrations in the plasma membrane that is converted into a second messenger; it has inositol (a carbohydrate) as its hydrophilic head group
inositol triphosphate (IP3)
cleavage product of PIP2 that is used for signaling within the cell
intercellular signaling
communication between cells
internal receptor
(also, intracellular receptor) receptor protein that is located in the cytosol of a cell and binds to ligands that pass through the plasma membrane
intracellular mediator
(also, second messenger) small molecule that transmits signals within a cell
intracellular signaling
communication within cells
ion channel-linked receptor
cell-surface receptor that forms a plasma membrane channel, which opens when a ligand binds to the extracellular domain (ligand-gated channels)
kinase
enzyme that catalyzes the transfer of a phosphate group from ATP to another molecule
ligand
molecule produced by a signaling cell that binds with a specific receptor, delivering a signal in the process
mating factor
signaling molecule secreted by yeast cells to communicate to nearby yeast cells that they are available to mate and communicating their mating orientation
neurotransmitter
chemical ligand that carries a signal from one nerve cell to the next
paracrine signal
signal between nearby cells that is delivered by ligands traveling in the liquid medium in the space between the cells
phosphatase
enzyme that removes the phosphate group from a molecule that has been previously phosphorylated
phosphodiesterase
enzyme that degrades cAMP, producing AMP, to terminate signaling
quorum sensing
method of cellular communication used by bacteria that informs them of the abundance of similar (or different) bacteria in the environment
receptor
protein in or on a target cell that bind to ligands
second messenger
small, non-protein molecule that propagates a signal within the cell after activation of a receptor causes its release
signal integration
interaction of signals from two or more different cell-surface receptors that merge to activate the same response in the cell
signal transduction
propagation of the signal through the cytoplasm (and sometimes also the nucleus) of the cell
signaling cell
cell that releases signal molecules that allow communication with another cell
signaling pathway
(also signaling cascade) chain of events that occurs in the cytoplasm of the cell to propagate the signal from the plasma membrane to produce a response
synaptic signal
chemical signal (neurotransmitter) that travels between nerve cells
target cell
cell that has a receptor for a signal or ligand from a signaling cell