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Test Bank for Ch 23 Beckers world of the cell 10th Edition by Jeff Hardin
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Test Bank for Ch 23 Beckers world ofthe cell 10th Edition by Jeff Hardin
Endocrine Signals - ANSProduced far from the target tissue,reach via the circulatory system
Paracrine Signals - ANSdiffusable, short range
Juxtacrine Signals - ANSrequire physical contact between sending and receiving cells, close
range
Autocrine Signals - ANSact on the same cell that produces them
ligand - ANSthe messenger that binds to a target receptor
Secondary Messengers - ANSsmall molecules or ions that relay signals, a cascade of changes
Signal transduction - ANSthe ability of a cell to respond to ligand-receptor bingding by altering
its behavior or gene expression
When receptors are occupied for too long of a time what happens? - ANSthe cell adapts to no
longer responding to the ligand
Cells adapting to signals, alterations to the reeptor that lower its affinity for the ligand, a shut off
response - ANSdesensitization
Agonists - ANSdrugs that activate the receptor they are bound to
Antagonists - ANSbind receptors without triggering a change and prevent the naturally occurring
messenger from activating the receptor
Once a ligand binds to a receptor it either induces a change in receptor conformation or causes
receptors to cluster, what happens next? - ANSa preprogrammed sequence of events inside the
cell either through a primary messenger or continuing on to a secondary messenger
What are the pathways of signal integration? - ANSa single receptor can activate multiple
pathways or multiple pathways can converge in to onto the same molecules
What are three examples of what can happen in response to a ligand binding? - ANSIt activates
multiple pathways, a single pathway, or different receptors activate different pathways; one
affects the other.
, What is signal amplification? - ANSthe multiplication of the effect of the signal, by very small
quantities that elicit a response from a target cell, resulting in a cascade of events
What are the two basic types of receptors? - ANSligand-gated channels and plasma membrane
receptors
What are the two types of plasma membrane receptors? - ANSThose linked to G-proteins and
those linked to protein kinases
What happens when a ligand binds to the G Protein-linked family? - ANSIt activates a particular
G Protein
What is the structure of G protein-linked receptors? - ANS7 transmembrane alpha helices
connected by alternating cytosolic or extracellular loops, these have unique messenger-binding
sites
What are heterotrimeric G Proteins? - ANSThey have 3 subunits and mediate signal
transduction through G protein-linked receptors Galpha Gbeta Gy
What is the purpose of Galpha subunit? - ANSIt is the largest subunit of Gaby, it binds to GDP
and GTP, when it binds to GTP it detaches from the other subunits which are permanently
bound
What is the function of the G protein? - ANSthe change in receptor conformation when a ligand
binds to the receptor causes the G protein to release its GDP, then Galpha binds to new GTP
molecule and leaves the comples, depending on the G protein either the Galpha or Gbetay
initiates signal trasnduction
When does G protein become inactive? - ANSThe dephosphoralation of GTP or the absence of
a ligand
What is cyclic AMP? - ANSa secondary messenger that is formed by cytosolic ATP by adenylyl
cyclase (from the plasma membrae)
What happens to cAMP when the G protein becomes inactive? - ANSadenylyl cyclase stops
making new cAMP, the remains of cAMP is degraded to AMP by phosphodiesterase
What is the function of cAMP? - ANSIts main target is protein kinase A (PKA) by regulating it by
separating regulatory and catalytic subunits.
What is the function of PKA? - ANSIt phosphorylates a variety of proteins on serine or threonine
residues, using ATP as a source of phosphate
What is IP3? - ANSA second messenger generated by the activation of phospholipase C
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