Module 6: Signal Transduction Mechanism Flashcards
Extracellular messages
messages from outside of the cell
4 types of messengers
Hormones: act at a distance (long distances from remote locations)
NTs: secretion close to target cells
(locally over very short distances)
Pheromones: act upon cells in different organism
Growth Factors: act at various distances
3 types of hormones
Peptide: short chain of linked aa
(insulin/glucagon)
Steroids: derived from lipid cholesterol
(vitamin D/estrogen)
Amino acid (amine) derivative: derived from modified aa (epinephrine/thyroxine)
Hormones
small molecules secreted by endocrine glands which travel long distances
through the bloodstream and bind to specific receptors on/in target cells
Epinephrine
secreted from the adrenal gland
promotes generation of energy (ATP) in muscle when it is required for exercise
Glucagon
secreted by the pancreas
acts on the liver to promote glycogen breakdown and gluconeogenesis when blood glucose levels are low
Insulin
secreted by the pancreas
promotes uptake of glucose into cells when blood glucose levels are high
3 steps of cell signalling
- Reception of the extracellular signal
- Transduction of the signal from the outside of the cell to the inside of the cell
- Cellular response to the signal
- Reception
Hormones (or ligands) act on their target cells by binding to receptors
ex: Epinephrine=ligand binds to beta adrenergic receptor
- Transduction
describe G-pr-
Transducer= G pr-
G pr-: heterotrimeric protein made up of alpha, beta and gamma subunits
Binding of hormone–>conformational change in receptor–>stimulates exchange of the bound GDP for GTP
GDP bound=G pr- inactive
GTP bound=active
- Response
describe adenylate cyclase and cAMP
Effector=adenylate cyclase
Active G pr- activates adenylate cyclase
Adenylate cyclase: catalyzes the conversion of ATP to cAMP
cAMP=second messenger
cAMP cellular response
cAMP activates kinase A by binding to it
active kinase A phosphorylates phosphorylase kinase b (become active)
active phosphorylase b kinase then activates glycogen phosphorylase
glycogen phosphorylase b =dephosphorylated, inactive
glycogen phosphorylase a =phosphorylated, active
active glycogen phosphorylase a then catalyzes the breakdown of glycogen, releasing glucose-1-phosphate for degradation and ATP synthesis to support muscle contraction
Insulin example
what is the message, messenger, transduction of the signal
Message: intake of a meal
Messenger: insulin released from pancreas
Transduction: signals to the target cells in muscle and adipose tissue to take up the glucose and either use it or store it away
Insulin signalling pathway
when insulin (signal/messenger) binds to receptor (receives signal), tyrosine kinase activated which activates another mech where PIP3 (second messenger) is synthesized GLUT4 pr- relocalized to the plasma membrane and responsible for taking up glucose from the bloodstream after a meal (cellular response)
