Lecture 11 Flashcards
cell signaling phases
signal reception
signal trasnduction
cellular response
transduction
converisonof one type of signal to another
often involved many steps and diff molecules called intracellular signalling molecules.
types of signals in cell signaling
proteins, peptides, aa, steroids, fatty acids derivatives, gases.
paracrine
from signal cells to nearby cells
signals include growth factors, inflammatory factors and gases
a local mediator is released, receptors on taret cell bind to it, signal is shared
neuronal
from a neuron to target
NT’s are released from terminal through synapse to receptors on target cells
contact dependent
siganling cell has mb bound signing contact, binds to the receptor found on the mb of the target cells
endocrine
if signaling cell is very far, uses circ system to travel from hormone secreting gland to the target cell.
diff bn intracellular receptors vs cell-surface receptors.
intracellular recepotrs for small hydrophobic molecules, (or hormones)
cell surface receptors = for large and hydrophilic molecules that can’t pass through mb
cortisol binding to intracellular receptors, example.
cortisol - fat soluble - passes through mb and binds to cortisol receptor.
**cortisol receptor = when is not bound to cortisol, is bound to a chaperone protein = this complex can’t enter the nucleus
receptor and cortisol can enter the nucleus through the pores.
cortisol can reg transctipiotn of several genes, cell responds by transcribing said genes.
how dissolved gases can enter the cell and activate intracellular enzymes.
acetylcholine is the sigma for the endothelial cells to make NO
is made, and released, then diffuses twds smooth muscles of vessels,
in muscles, binds to enzymes, makes GTP to cAMP, blah blah, smooth muscles relax and vessels are dilated.
3 main classes of cell-surface receptors
- ion channel coupled receptors
- G protein coupled receipts.
- enzyme coupled receptors
ion Chanel coupled receptors,
w/o signal molecule, channel closed, ions can’t move past mb
w signal, molecule binds, changes conformation, channel opens, ions can pass through.
G protein coupled receptors
In the mb, there is an inactive receptor , inactive G protein and an inactive enzyme
signal moleceule binds to receptor, activates the receptor, binds to the G protein and activates it
activated G protein unbinds to receptor, one part of it goes to bind with inactive enzyme and activates it, the 2/3 part left is still activated.
enzyme coupled receptors
there are 2 inactive catalytic domaines. and a signal in form of a dimer
dimer binds to 2 inactive catalytic domains, and activates them
ORRRRRRR
inactive receptor binds to signal molecule, and the now active receptor activates an assoc enzyme
ok so the signal molecule binds now what
the cell surface binds the signals and create new intracellular signals
each intercell. signal molecule activates or generate the next signaling molecule (can be proteins or small messenger molecs)
effector portiens directly affect the behaviour of the target cell.
relaying an incoming signal
passing the message along
amplified
make the signal stronger or one sigaling molecule activates many downstream molecs.
1 receptor activates 10 proteins, each protein activates many enzymes, each enzymes produces thousands of cAMP messengers,
large repsonse from small signal.
integrate
protein taking multiple signals form diff pathways, and combines them to decide the cells response.
distribute
signaling protein passes the signal to multiple targets, causing diverse responses.
protein gets activated and triggers - change in gene expression, changes metabolism, activates smth and deactivate smth else., for ex.
feedback
the activity of proteins and enzymes int eh pathway is reg by + or - feedback
many intracellular signaling proteins act as molecule switches
fluctuate bn inactive and active states
active = stimulate/supress other proteins in the pathway
one class = activated by phos and dephosphorylation.
other class = activated by GTP binding
fast/slow cell responses
fast; changes in
cell movement, shape, metabolism or just secretions
slow,
cell differentiation/division, or growth
each cell responds to limited sets of extracellular signals
cells can’t respond to all signals, each cell has its own type of receptors at its surface
what each has on the inside also matters, = receptor proteins inside determine response of cells
interpretation of signals,
same signal in diff cells =….
same signal + diff cells = diff responses
each cell receives and interprets the signal differently
interpretation depends on receptors, effector proteins nad any additional signals received by the cell
effect of combination of received signals
ABC = survice
ABC + DE = grow and divide
ABC + FG = differentiate
no signal/other signal = die.
diff combination = diff response needed
