Midterm 2 - Principles of Hormone Action Flashcards
where are hormones secreted
into blood
where do hormones act
at a distance from the release site
what do hormones need to be able to do
travel in the blood (solubility)
survive long enough
be active at the target site
what do hormones trigger
specific actions in specific target cells
what is the requirement for specific recognition
receptors
what is the principle of action based on
hormone biochemical structure and properties
what are the key to hormone action
receptors
what initiate the effects of hormones
the hormones bind to receptors
what do lipophilic hormones do
diffuse out of producing cells
circulate mainly bound to carriers in the blood
diffuse in target cells to intracellular receptors
what do water-soluble hormones do
they are secreted via exocytosis
they circulate freely in blood
stay out of target cell to surface (extracellular) receptor
what are examples of lipophilic hormones
steroid hormones
thyroid hormones
are lipophilic hormones soluble in water
no, circulate associated to carrier proteins
types of carriers for lipophilic hormones
specific
non specific
examples of specific lipophilic hormone carriers
globulins:
CBG
DBG
SHBG
TBG
examples of non-specific lipophilic hormone carriers
albumin
pre albumin
what are some reasonings for carrier proteins being big
they keep hormones in vessel
prevent hormone degradation
does all of a lipophilic hormone get carried
no - a small portion remains free and diffuses to the tissues
what is the free lipophilic hormone characteristics
the active portion, but also susceptible to degradation
what is the free form (active) lipophilic hormone involved in
feedback loops
what does the carrier serve as
hormone reservoir
hormone buffer
hormone protection
what do carrier proteins play a major role in
controlling lipophilic hormones
in nuclear hormone receptors, what does the ligand binding domain do
binds hormone
in nuclear hormone receptors, what does the DNA binding domain do
binds the DNA of target gene
in nuclear hormone receptors, what does the activation domain do
stimulates gene transcription
in nuclear hormone receptors, what is the orphan receptor
NHR is cloned by no ligand is found
what does the action of lipophilic hormones affect
the synthesis of new proteins by gene regulation = slow acting hormones
what is the major circulating form of thyroid hormones
T4 (thyroxine)
what happens to T4 when it enters the target cell
it is converted to T3 (try-iodo-thryonine)
what is the cellular active form of thyroid hormone
T3
what does T3 do
binds to its specific receptor after entering the nucleus
what happens to hormones after acting
hormones dissociate from the receptor and can be partly degraded in target cells, then go back to circulation and is degraded in the liver
can water soluble hormones pass the phospholipid membrane barrier
no
how are water soluble hormones secreted
in vesicles by exocytosis
how do water soluble hormones circulate
freely
what is the water soluble hormone that does not circulate freely (the exception)
IGF-1 circulates bound to carrier
what do water soluble hormones bind to
specific receptors on surface of target cell
do water soluble hormones enter cell to act
no - need secondary messengers
what is the key mediator between hormone and secondary messengers of water soluble hormones
receptor
for cell surface receptors, where is the hydrophobic region
hiding in the membrane’s phospholipids - transmembrane domain
for cell surface receptors, where are hydrophilic regions
outside (extracellular domain) and inside (intracellular domain) cell
what activates the intracellular secondary messenger
hormone-receptor
for G-protein coupled receptors, what are the messengers
adenylate cyclase (cAMP)
Phospholipase C; Ca2+
for tyrosine kinase receptor, what is the messenger
auto-phosphorylation
for the interleukin/cytokine family of receptors, what is the messenger
JAK-STAT
for the Serine kinase (TGFB) family of receptors, what is the messenger
SMADs
what do the 3 major types of G-proteins differ by
alpha-subunit
what is unique about the tyrosine kinase receptor
there is no need for a second messenger, directly phosphorylates target proteins
what are the 3 domains of the tyrosine kinase receptor
transmembrane domain
extracellular domain for ligand recognition
cytoplasmic domain
what does the cytoplasmic domain of the tyrosine kinase receptor have
an autophosphorylation site that transmits regulatory signals and contains ATP binding sites
examples of receptors for cytokine
GHwhat wh
prolactin
erythropoietin
interferons
interleukins
what do cytokine receptors not have
intrinsic kinase activity
what is the TGFB family mainly involved in
control of cell proliferation and differentiation
what are in the TGFB family
active
inhibit
MIS
what does the cascade of intracellular messenger do
amplifies the signal several thousand times
what do the specific effects of cell surface receptors on target cells depend on
the type and amount of messenger activated
what are the immediate effects of messenger activation
enzyme activation
exocytosis
what are the slow effects of messenger activation
stimulation of gene transcription, de novo protein synthesis
what happens to the receptor-hormone complex after signalling
it is internalised
how is the receptor-hormone complex internalized
fuses to lysosomes and degrades
dissociates and receptor is recycled to cell surface
why is the receptor-hormone complex internalized
need the termination of message to prevent desensitization
