cell signals and responses Flashcards
cell commicaiton methods
secretion
contact signalling via membrane bound molecules
contact signalling through gap junctions
contact signalling via gap junctons
small ions rapidly transferred between cells
chemical signalling secreted examples
endocrine
paracrine
autocrine
synaptic
endocrine
hormone produced and enter blood stream
carried to target cell
paracrine
local chemical mediator released
acts on cells in immediate evironment
autocrine
on itself
synaptic
neutrotransmittors released at synapses
diffuse to post synaptic cel
signal flow chart
signal
reception
transducer and transferred
responce
signals to cells
1) Growth factors
2) hormones
3) extracellular matrix (receptors can interact with the ECM)
4) chemicals
5) proteins
6) sugars
7) synaptic
cell responses
1) Growth (Cell division)
2) differentiation
3) metabolism
4) contract/relax
- eg muscle cells
5) apoptosis
6) gene transcription
7) secretion
8) migration
9) membrane charge
- eg excitable cell
what can a signal focus on
cell surface receptor
internal cell receptor
what happens on binding to cell surface receptor
translate extraceullar to intracellular signal
what can pass through the cell membrane
hydrophobic signal for intracellular receptors
transported to the nucleus
types of membrane receptors
G protein coupled (heptahelical) enzyme linked (receptor tyrosine kinases ion channels
characterisitcs of signal transduction
- specificity and high affinity
- amplification
- desensitisation when signal is present (may desensitise when fall below a threshold)
- integration of multiple signals to produce a unified responce
how many times does a G coupled receptor go through the membrane
7 times
what do G coupled protein receptors respond to
light
taste
smell
hormones
G protein coupled receptor
integral transmembrane protein (outside binds to signal, inside interacts with signalling molecules)
Initiates signalling through secondary messengers e.g. CAMP via G protines
G protein coupled receptor steps
1) Hormone binds to the G protein coupled receptor
2) Pink G protein is associated with the receptor, when inactive it is bound to GDP
3) When the hormone has bound, GDP is exchanged for GTP
4) This alters the structure of the G protein which is associated with the receptor
5) affinity is lost between the different subunits
6) The alpha unit with GTP is lost and can interact with other parts of the cell
what happens if the alpha subunit is bound to GDP (G coupled protein receptor)
G protein will reform
inactive state of complex returns
what type of receptor is Beta adrenergic receptor
G protein coupled receptor
what does Beta adrenergic receptor bind to
adrenaline
noradrealine
What is the beta adrenergic receptor targeted fro
beta blokers
B2 antagonists
(prevents signal by competing reducing blood pressure)
What can be added to 3 different amino acids
phosphate
phosphoryaltion and enzyme
kinase catalyses reaction of phosphate sticking to another moelcile
what removes phosphate
phosphatases
what are receptor tyrosine kinases
receptors on cell surface which are kinase
stick a phosphate on tyrosine
they are also enzymes themselves
what do receptor tyrosine kinases do
stick phosphate onto themselves
molecule binds, 2 diff subunits of protein comes together
forms dimer on cell surface
activate themselves by phsophroyaltion
reactions of cell surface receptors for growth factors cytokines and hormones
have intrinsic enzyme activity - unlike enzyme linked receptors
leads to change in charge once ligand binds
conformational change allows signalling molecules to bind and cascade
enzyme linked receptos
2 subunits come together
change in conformation allows associated enzyme to join
then has activity
- receptor itself does not have activity until the enzyme joints
ligand gated ion channel and types
receptor is an ion channel - ligand binds and opens io channel - voltage or mechanical gates Responce to ligan - change in membrane potential action potential
example of ligand gated receptor
GABAa receptor neurotransmittor - opens Cl- sensitive pore hyperpolarises neurone (inside cell is -) firing of AP
what can therapeutic targets do and effects of signalling
inhabit pathways by using targets to prevent signalling events occuring
- can be used in diseases, mutations in proteins ect, as these are dysregualted
examples of therapeutic targeters
small molecule inhibitors
monoclonal antibodies
