Glossary of Chapter 11 - Cell Communication

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Signal transduction pathway
the process by which a signal on a cell's surface is converted into a specific cellular response
Local regulator
a substance that influences cells in the vicinity of the releasing cell;
e.g., growth factor or neurotransmitter
chemicals that are used to to influence cells in other, more distant, areas of the body
G-protein linked receptor
a plasma membrane receptor that works with the help of a protein called a G protein;
contain seven alpha-helices spanning the membrane
G protein
part of the G-protein linked receptor that functions as a switch that is on or off depending on which of two guanine nucleotides is attached, GDP (inactive) or GTP (active)
Tyrosine kinase
part of the receptor protein on the cytoplasmic side of the membrane that functions like an enzyme;
catalyzes the transfer of phosphate groups from ATP to the amino acid tyrosine on a substrate protein
Tyrosine-kinase receptors
membrane receptors that attach phosphates to protein tyrosines
Ligand-gated ion channels
protein pores in the plasma membrane that open or close in response to a chemical signal, allowing or blocking the flow of specific ions, such as Na+ or Ca++
Protein kinase
the general name for an enzyme that transfers phosphate groups from ATP to a protein
Protein phosphatases
enzymes that remove phosphate groups from proteins
Second messengers
small, nonprotein, water-soluble molecules or ions;
small size facillitates the diffusion of second messenger throughout the cell;
cAMP and Ca++ are most common
cyclic AMP
a common second messenger
Adenylyl cyclase
an enzyme built into the plasma membrane of a cell that converts ATP to cAMP in resposne to an extracellular signal
Diacylglycerol (DAG)
Inositol trisphosphate (IP3)
two messengers produced by cleavage of a certain kind of phospholipid in the plasma membrane;
stimulates the release of Ca++ from the ER in
a Ca++ binding protein present at high levels in eukaryotic cells that mediates many calcium-regulated processes in cells;
Ca++ binds to calmodulin, causing it to change its configuration and act on other proteins

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