2nd messengers I Flashcards
4 classes of cellular signaling molecules
hormones
local mediators
neurotransmitters
growth factos
growth factos
signaling molecules that regulate cell proliferation and differentiation
hormones
have regulatory effects on specific organs or tissues at a site distrant from hormone secretion
how do hydrophilic hormones work
bind to plasma membrane receptor
either generate intracellular second messenger or activate receptor enzymatic acitivty
what do hydrophilic hormones generally result in
changes in activity of meabolic enzymes (typically rapid)
what are lipophilic hormones often derived from
cholesterol
function of lipophlic hormones
pass through plasma membrane and bind receptors in nucleus or ceyptoplasm
what does binding of lipophilic hormones result in
altered transcription (slower response)
how do water soluble hormones mainly function
binding to specific receptors
GDP bound form is waht
inactive
GTP bound form is what
active
GTPase
hydrolyze GTP to GDP and can turn themselves off
what happens when the G protein gets acitived
dissociation of the alph asubunit from the beta-gamma dimer
G-proteins frequenctly activate proteins that generate what
intracellular second messengers
Gs generally does what
stimulates activity of enzymes
Gi generally does what
inhibit activity of certain enzymes
Gq generally does what
stimulates activity of certain enzymes
2 imporant enzymes that are directly modulated by bindign to activated G proteins
adenylate cyclase, phospholipase C
what does adenylate cyclase catalyze the formation of
cAMP and PPi
hydrolysis of PPi by pyrophosphatease acitvies drives what
reaction in direction of cAMP formation
is the adenylate cyclase reaction reversible or irreveresble
irreversible
what is the principle target for cAMP
protein serine/threonine kinase (PKA)
how is cAMP signaling shu toff
degrated by phosphodiesterases
interstrinc GTPase
how does glucagon affect cAMP and PKA
elevate cAMP
activate PKA
glycogen
stoarge form of glucose
where aer the main deposits of glycogen
liver and skeletal msucle
function of glycogen in the liver
buffer blood glucose during times of fasting
function of epinephrine
glycogenolysis in muscle
fat hydrolysis in adipose
incrase rate and strength of HR
function of glucagon
glycogenolysis in liver
fat hydrolysis in adipose tissue
function of arginine vasopression
water reabsorption in kidney
function of phospholipiase C
hydrolyzes phosphatidlyinosital 4,5 bisphosphate to generate IP3 and DAG
IP3 charactersitics
water soluble
diffuses into cytosole
DAG characteristics
lipophilic, remains membrane associated
function of IP3
binds to receptors that open Ca++ channels.
affects of Ca++
help activate protein kinase C
bind calmodule
function of DAG
help active PKC
how do you turn of signaling from phosphatidylinositol 4,5-bisphosphate
receptor down regulation/interanlization and degration
protein phosphateases reverse action of PKC
how do you get rid of Ca++
pump out of cytosal
how do you stop IP3
dephosphorylated by specific phosphatase, converting it to a derviative that does not open the Ca++ channel
how do you stop DAG
phosphorylated, or hydrolyzed
