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20 Cards in this Set

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Signal transduction pathway
Process by which signal on the cell surface is converted into a specific cell response
local regulator
influences local cells
paracrine
single cell produces growth factor that stimulates growth of local cells.
autocrine
is a form of signaling in which a cell secretes a chemical messenger (called the autocrine agent) that signals the same cell.
3 steps from cell signal to response
1) Reception - detects signal. 2) Transduction - binding of a signal molecule changes the receptor protein. Transduction converts the signal to a form that can bring about a specific cellular response. 3) Response
G protein-linked receptors
plasma membrane receptors that work with the help of a G protein. Made of 7 alpha helices spanning the membrane. Cytoplasmic side is the G protein which acts like a switch binding either GDP or GTP. When GDP is bound it is inactive.
Tyrosine Kinase receptors
Designed to simulate more than one pathway at once. Tyrosine kinase on cytosolic side transfers phosphate from ATP to tyrosine. Has a single alpha helix binding site extracellularly. Cytosolically it has multiple tyrosine kinase receptor proteins.
Steps to activation of tyrosine kinase
Ligand binds causing 2 receptor polypeptides to form a dimer. Aggregation activates tyrosine kinase parts to add phosphates to tyrosine in the tail of the other. Now activated it is a recognized by relay proteins. Each binds to a special phosphorylated tyrosine undergoing structural changes that activates them.
None
Ligand gated ion channels
protein pores that open to allow ions through. These are important in transmission of electrical signals down neurons or muscle fibers.
Intracellular receptors
lipid soluble hormones and others that can diffuse through the cell membrane bind to cytosolic receptors activating them and are then transported into the nucleus. The cell is signal physically brought into the nucleus rather than having a relay chemical.
Protein kinase
transfers phosphate groups from ATP to a protein. Usually a protein kinase transports their substrates onto serine or threonine.
Many of the molecules in signal transduction pathways are protein kinases and they often act on each other.
Second messenger
part of the signal transduction pathway. Small water soluble non-proteins. cAMP and Ca2+ are second messengers.
Cyclic AMP
second messenger. Immediate effect is usually the activation of a serine/threonine kinase called protein kinase A
Adenylyl cyclase
enzyme built into the plasma membrane that converts ATP to cyclic AMP in response to an outside stimulation.
Further fine tuning of metabolism is provided by other G protein systems that inhibit adenylyl cyclase.
Diacylglycerol (DAG)
second messenger created by a cleavage of a phospholipid in the plasma membrane
Inositol triphosphate (IP3)
second messenger created by a cleavage of a phospholipid in the plasma membrane. Stimulates the release of Ca2+ from the ER.
Calmodulin
Ca2+ binding protein found in high levels in animal cells (up to 1% of animal protein). Mediates many Ca2+ regulated processes. When Ca2+binds calmodulin changes shape and binds to other proteins activating or inactivating them.
dimer
a molecule composed of two identical subunits or monomers linked together. The molecules are connected with a covalent bond or more weak interactions such as hydrogen bond.