Chapter 16 Flashcards
adaptation
Adjustment of sensitivity following repeated stimulation;
allows a cell or organism to register small changes in a
signal despite a high background level of stimulation.
adenylyl cyclase
Enzyme that catalyzes the formation of cyclic AMP from
ATP; an important component in some intracellular
signaling pathways.
Ca2+/calmodulin-dependant protein kinase (CaM-kinase)
Enzyme that phosphorylates target proteins in response to
an increase in Ca2+ ion concentration through its interaction
with the Ca2+-binding protein calmodulin.
cell signaling
The molecular mechanisms by which cells detect and
respond to external stimuli and send messages to other
cells.
cyclic AMP
Small intracellular signaling molecule generated from
ATP in response to hormonal stimulation of cell-surface
receptors.
Cyclic-AMP-dependant protein kinase (PKA)
Enzyme that phosphorylates target proteins in response to
a rise in intracellular cyclic AMP concentration.
diacylglycerol (DAG)
Small messenger molecule produced by the cleavage
of membrane inositol phospholipids in response to
extracellular signals. Helps activate protein kinase C.
enzyme-coupled receptor
Transmembrane protein that, when stimulated by the
binding of a ligand, activates an intracellular enzyme (either
a separate enzyme or part of the receptor itself).
extracellular signal molecule
Complex network of polysaccharides (such as
glycosaminoglycans or cellulose) and proteins (such as
collagen) secreted by cells. A structural component of tissues
that also influences their development and physiology.
G protein
A membrane-bound GTP-binding protein involved in
intracellular signaling; composed of three subunits, this
intermediary is usually activated by the binding of a
hormone or other ligand to a transmembrane receptor.
G-protein-coupled receptor (GPCR)
Cell-surface receptor that associates with
an intracellular trimeric GTP-binding
protein (G protein) after activation by an
extracellular ligand. These receptors are
embedded in the membrane by seven
transmembrane α helices.
GTP-binding protein
Intracellular signaling protein whose activity is determined
by its association with either GTP or GDP. Includes both
trimeric G proteins and monomeric GTPases, such as Ras.
hormone
Extracellular signal molecule that is secreted and
transported via the bloodstream (in animals) or the sap (in
plants) to target tissues on which it exerts a specific effect.
inositol 1,4,5-triphosphate (IP3)
Small intracellular signaling molecule that triggers the
release of Ca2+ from the endoplasmic reticulum into the
cytosol; produced when a signal molecule activates a
membrane-bound protein called phospholipase C.
inositol phospholipid
Minor lipid component of plasma membranes that plays a
part in signal transduction in eukaryotic cells; cleavage yields
two small messenger molecules, IP3 and diacylglycerol.
intracellular signaling pathway
A set of proteins and small-molecule second messengers
that interact with each other to relay a signal from the
cell membrane to its final destination in the cytoplasm or
nucleus.
ion-channel-coupled receptor
Transmembrane receptor protein or
protein complex that opens in response to
the binding of a ligand to its external face,
allowing the passage of a specific inorganic
ion.
local mediator
Secreted signal molecule that acts at a short range on
adjacent cells.
molecular switch
Intracellular signaling protein that toggles between an
active and inactive state in response to receiving a signal.
neurotransmitter
Small signaling molecule secreted by a nerve cell at a
synapse to transmit information to a postsynaptic cell.
Examples include acetylcholine, glutamate, GABA, and
glycine.
nitric oxide (NO)
Locally acting gaseous signal molecule that diffuses
across cell membranes to affect the activity of intracellular
proteins.
nuclear receptor
Protein inside a eukaryotic cell that, on binding to a signal
molecule, enters the nucleus and regulates transcription.
phospholipase C
Enzyme associated with the plasma membrane that
generates two small messenger molecules in response to
activation.
protein kinase
Enzyme that catalyzes the transfer of a phosphate group
from ATP to a specific amino acid side chain on a target
protein.
protein kinase C
Enzyme that catalyzes the transfer of a phosphate group
from ATP to a specific amino acid side chain on a target
protein.
protein phosphotase
Enzyme that catalyzes the removal of a phosphate
group from a protein, often with high specificity for the
phosphorylated site.
receptor
Protein that recognizes and responds to a specific signal
molecule
receptor tyrosine kinase (RTK)
Enzyme-coupled receptor in which the intracellular domain has a tyrosine kinase activity, which is activated by ligand binding to the receptor’s extracellular domain.
serine/threonine kinase
Enzyme that phosphorylates target proteins on serines or
threonines.
signal transduction
Conversion of an impulse or stimulus from one physical or
chemical form to another. In cell biology, the process by
which a cell responds to an extracellular signal.
tyrosine kinase
Enzyme that phosphorylates target proteins on tyrosines.
