L11-Cell Signaling Flashcards
release of chemical compound where the same cell is the target cell
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stages of cell signaling.
reception, transduction and response.
reception definition?
the binding of the chemical compound/ligand to the receptor protein.
Transduction?
the cascade of events initiated by the occupancy of the receptor protein where relay molecules are activated and cause activation of other relay molecules.
types of relay molecules?
mostly enzymes and proteins but can be non proteins and ions as well.
what molecules are secondary messengers?
relay molecules are secondary messages transmitting signal downstream.
transduction cascade causes……….?
it causes the activation of proteins through the process of phosphorylation by kinases enzymes and deactivation of proteins through the process of dephosphorylation by phosphates enzyme.
Response definition?
the last step where the signal causes cellular response like secretion, contraction cell division and differentiation.
what are the 2 different types of receptors
A) cell surface receptors
B) intracellular receptors
types of cell surface receptors?
A) ligand gated ion channels
B) G-coupled protein receptor
C) Enzyme linked receptor.
explain the mechanism of ligand gated ion channels.
they are closed channels that have a receptor that binds with a specific ligand when the ligand binds with receptor it causes the channel to open and allow ions to pass through and when the ligand detaches the channel will close again. some channels are open and closes when ligand binds.
where can you find ligand gated ion channel?
Neurones and muscle cells.
Explain cystic fibrosis?
Gene mutation in chloride ion channels that are present on the surface of the epithelial cells. this defect doesn’t allow chloride ions out of the cell and reduce viscosity of mucus therefore, patients experience difficulty breathing.
Explain the G protein coupled receptor.
upon binding of ligand the protein detaches form the receptor protein and the alpha subunit seperates from the rest of the protein and the GDP molecule is replaced by GTP and goes on to activate other relay molecules usually activates kinases that initiates phosphorylation.
what are the subunits of the G-protein?
gamme beta and alpha subunits.
what happens if the protein is active for too long?
initiates gene expression.
state all the types of G proteins and their function
A) Gs –> stimulates adenylate cyclase (cyclic AMP pathway)
B) Gi –> inhibits adenylate cyclase ( cyclic AMP pathway)
C) Gq –> stimulates phospholipase (phosphinositide pathway)
D) G0 –> inhibits calcium ion channels.
the cholera toxins effects on the body
the toxins released from the bacterium called Vibrio Cholerae causes ADP ribosylation of the Gs protein making the adenylate cyclase to become more active leading to an extended response cause secretion of water and chloride in the gut and constant contraction of intestine muscles causing severe and potentially fatal diarrhea
the pertussis toxins effect on the body?
The toxins released also causes ADP ribosylation of Gi protein therefore the adenylate cyclase will not be inhibited and will be active longer causing an extended response. therefore, contractions of the airway occur causing difficulty breathing and severe coughing.
explain the mechanism of the enzyme linked receptor
the ligand binds with receptor and the receptor is made of 2 subunits.
what is special about enzyme linked receptors?
they have intrinsic enzyme activity or have enzyme closely attached to it.
what are the 4 main types of enzymes linked receptor?
A) Receptor tyrosine kinases
B) Receptor Serine/threonine kinase
C) Tyrosine kinase associated receptors
D) receptor gunnel cyclase.
receptor tyrosine kinase?
when the ligand binds with receptor, 2 receptors dimerizes activate their intrinsic tyrosine kinase inducing phosphorylation. its also the receptor for insulin hormone.
receptor serine/threonine kinases?
upon ligand binding it activates their intrinsic kinase activity.
tyrosine kinase associate receptor
upon binding of ligand it activates attached protein that phosphorylates tyrosine and initiates kinase
receptor guanyl cyclase?
when ligand binds with receptor guanyl cyclase is activated and cGMP is produced as a secondary messenger
what is RAS?
they are small proteins that are down stream from the receptor tyrosine kinase that can easily turn oncogenic, it becomes constitutively active causing uncontrollable division and cancerous transformation.
