Chapter 16 Key Terms

Question 1

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.

Answer 1

Adaptation

Question 2

Enzyme that phosphorylates target proteins in response to an increase in Ca+2 ion concentration through its interaction with the Ca+2 binding protein calmodulin.

Answer 2

Ca+2/calmodulin-dependent protein kinase (CaM kinase)

Question 3

The molecular mechanisms by which cells detect and respond to external stimuli and send messages to other cells.

Answer 3

Cell signaling

Question 4

Small intracellular signaling molecule generated from ATP in response to hormonal stimulation of cell-surface receptors

Answer 4

Cyclic AMP

Question 5

Enzyme that phosphorylates target proteins in response to a rise in intracellular cyclic AMP concentration

Answer 5

Cyclic-AMP-dependent protein kinase (protein Kinase A, PKA)

Question 6

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).

Answer 6

Enzyme-coupled receptor

Question 7

Any molecule present outside the cell that can elicit a response inside the cell when the molecule binds to a receptor.

Answer 7

Extracellular signal molecule

Question 8

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.

Answer 8

G protein

Question 9

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 alpha helices.

Answer 9

G-protein-coupled receptor (GPCR)

Question 10

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.

Answer 10

GTP-binding protein

Question 11

Extracellular signal molecule that is secreted and transported via the bloodstream (in animals) or the sap (in plants) to target tisues on which it exerts a specific effect.

Answer 11

Hormone

Question 12

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.

Answer 12

Insitol phospholipid

Question 13

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.

Answer 13

Intracellular signaling pathway

Question 14

Transmembrane receptor protein or protein complex that opens in resposne to the binding of a ligand to its external face, allowing the passage of a specific inorganic ion.

Answer 14

Ion-channel-coupled receptor

Question 15

Secreted signal molecule that acts at a short range on adjacent cells.

Answer 15

Local mediator

Question 16

Mitogen-activated protein kinase. Signaling molecule that is the final kinase in a three-kinase sequence called the MAP kinase signaling module.

Answer 16

MAP kinase

Question 17

Intracellular signaling protein that toggles between an active and inactive state in response to receiving a signal.

Answer 17

Molecular switch

Question 18

Small, single-subunit GTP-binding protein. Proteins of this family, such as Ras and Rho, are part of many different signaling pathways.

Answer 18

Monomeric GTPase

Question 19

Small signaling molecule secreted by a nerve cell at a synapse to transmit informaion to a postsynaptic cell. Examples include acetylcholine, glutamate, GABA, and glycine.

Answer 19

Neurotransmitter

Question 20

Locally acting gaseous signal molecule that diffuses across cell membranes to affect the activity of intracellular proteins.

Answer 20

Nitric oxide (NO)

Question 21

Protein inside a eukaryotic cell that, on binding to a signal molecule, enters the nucleus and regulates transcription.

Answer 21

Nuclear receptor

Question 22

One of a large family of small GTP binding proteins (the monomeric GTPases) that helps relay signals from cell-surface receptors to the nucleus. Many human cancers contain an overactive mutant form of the protein.

Answer 22

Ras

Question 23

Protein that recognizes and responds to a specific signal molecule.

Answer 23

Receptor

Question 24

Enzyme-coupled receptor that phosphorylates target proteins on serine or threonine.

Answer 24

Receptor serine/threonine kinase

Question 25

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.

Answer 25

Receptor tyrosine kinase (RTK)

Question 26

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.

Answer 26

Signal transduction

Question 27

Nucleotide, lipid, ion, or other small molecule generated or released in response to an extracellular signal. Examples include cAMP, IP3, and Ca+2. Also called second messengers.

Answer 27

Small intracellular signaling molecule

Question 28

Hydrophobic signal molecule related to cholesterol; can pass through the plasma membrane to interact with intracellular receptors that affect gene expression in the target cell. Examples include estrogen and testosterone.

Answer 28

Steroid hormone

Question 29

Enzyme that phosphorylates target proteins on tyrosines.

Answer 29

Tyrosine kinase