AP Biology Chapter 9 Key Terms

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