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Chapter 11 Terms
Cell Communication
16
Biology
Undergraduate 1
02/09/2010

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Term
signal transduction pathway
Definition
A series of steps linking a mechanical or chemical stimulus to a specific cellular response.
Term
local regulator
Definition
A secreted molecule that influences cells near where it is secreted.
Term
hormone
Definition
In multicellular organisms, one of many types of secreted chemicals that are formed in specialized cells, travel in body fluids, and act on specific target cells in other parts of the body to change their functioning.
Term
Ligand (lig′-und)
Definition
A molecule that binds specifically to another molecule, usually a larger one.
Term
G protein-coupled receptor
Definition
A signal receptor protein in the plasma membrane that responds to the binding of a signaling molecule by activating a G protein. Also called a G protein-linked receptor.
Term
G protein
Definition
A GTP-binding protein that relays signals from a plasma membrane signal receptor, known as a G protein-coupled receptor, to other signal transduction proteins inside the cell.
Term
receptor tyrosine kinase
Definition
A receptor protein in the plasma membrane, the cytoplasmic (intracellular) part of which can catalyze the transfer of a phosphate group from ATP to a tyrosine on another protein. Receptor tyrosine kinases often respond to the binding of a signaling molecule by dimerizing and then phosphorylating a tyrosine on the cytoplasmic portion of the other receptor in the dimer. The phosphorylated tyrosines on the receptors then activate other signal transduction proteins within the cell.
Term
ligand-gated ion channel
Definition
A protein pore in cellular membranes that opens or closes in response to a signaling chemical (its ligand), allowing or blocking the flow of specific ions.
Term
protein kinase
Definition
An enzyme that transfers phosphate groups from ATP to a protein, thus phosphorylating the protein.
Term
protein phosphatase
Definition
An enzyme that removes phosphate groups from (dephosphorylates) proteins, often functioning to reverse the effect of a protein kinase.
Term
second messenger
Definition
A small, nonprotein, water-soluble molecule or ion, such as a calcium ion (Ca) or cyclic AMP, that relays a signal to a cell’s interior in response to a signaling molecule bound by a signal receptor protein.
Term
cyclic AMP (cAMP)
Definition
Cyclic adenosine monophosphate, a ring-shaped molecule made from ATP that is a common intracellular signaling molecule (second messenger) in eukaryotic cells. It is also a regulator of some bacterial operons.
Term
adenylyl cyclase (uh-den′-uh-lil)
Definition
An enzyme that converts ATP to cyclic AMP in response to a signal.
Term
inositol trisphosphate (IP3) (in-ō′-suh-tol)
Definition
A second messenger that functions as an intermediate between certain nonsteroid hormones and a third messenger, a rise in cytoplasmic Ca2+ concentration.
Term
diacylglycerol (DAG) (dī′-a-sil-glis′-er-ol)
Definition
A second messenger produced by the cleavage of a certain kind of phospholipid in the plasma membrane.
Term
Apoptosis (ā-puh-tō′-sus)
Definition
A program of controlled cell suicide, which is brought about by signals that trigger the activation of a cascade of suicide proteins in the cell destined to die.
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