CHAPTER 5: Cell Signaling Flashcards
receptors
target-cell proteins that chemical messengers bind to which changes the conformation of it by activating it
signal transduction
a sequence of events in the cell leading to the cell’s response to that messenger
“signal” = receptor activation
“transduction” = process by which a stimulus is transformed into a response
arriving chemical messengers bind to ______ parts of receptor and signal transduction events occur in ______ regions
extracellular, intracellular
name all the domains in transmembrane receptor for a hormone
-n-terminal
-DNA-binding domain
-hinge
-ligand-binding domain
key distinction of plasma membrane receptors and all intracellular ones
PM receptors can transduce signals without interacting with DNA
4 major features of receptor & ligand interactions
1) specificity = ability of a receptor to bind only one type or limited number of chemical messengers
2) saturation = the degree to which receptors are occupied by messengers
3) affinity = the strength of binding
4) competition = different molecules competing with a ligand for binding to its receptor
antagonist
a molecule that competes with a ligand for binding to its receptor by preventing the actions of the natural ligand (ex: antihistimines)
agonist
a chemical messenger that binds to a receptor and triggers the cell’s response
down-regulation
a decrease in total number of receptors for a given messenger –> chronically high concentration of messenger
up-regulation
an increase in total number of receptors for a given messenger –> chronically low concentration of messenger
super-sensitivity (associated with up0regulation)
increased responsiveness of a target cell to a given messenger
internalization is associated with ____ and means:
down-regulation, messenger-receptor complex is taken into the cell by endocytosis
true or false: a single cell may express multiple receptor types
true
receptor activation
initial step leading to the cell’s responses to the messenger
true or false: more than one gene may be subject to control by a single receptor type
true
true or false: the transcription of gene(s) is always increased
false (ex: cortisol)
first messengers
EC chemical messengers that reach the cell and bind to their specific PM receptors
second messengers
substances that enter or are generated in the cytoplasm as a result of receptor activation by the first messenger
protein kinase
enzyme that phosphorylates other proteins by transferring a phosphate group to them from ATP
receptor tyrosine kinases
receptors that possess intrinsic enzyme activity - specifically phosphorylate tyrosine residues
sequence of receptors (intrinsic tyrosine kinase activity)
1) binding of a specific messenger to the receptor changes the conformation of the receptor
2) autophosphorylation of the receptor, then those phosphotyrosines serve as docking sites for cytoplasmic proteins
3) bound docking proteins then bind and activate other proteins, which in turn activate one or more signaling pathways
guanylyl cyclase
catalyzes the formation of molecule cyclic GMP (which functions as a second messenger to activate cGMP-dependent protein kinase)
janus kinases
receptor and janus kinase functions as a unit
activated by the binding of a first messenger to the receptor, causing a conformational change in the receptor
g-proteins
protein complex bound to the inactive receptor located on the cytosolic surface with an alpha, beta, and gamma subunit
alpha subunit binds ____ and ____
GDP and GTP
phospholipase C
plasma membrane enzyme that catalyzes formation of second messengers DAG and IP3
eicosanoids
activates phospholipase A
