8 cell communication Flashcards
signal transduction
changing the form of a signal, either by releasing another chemical signal or binding to another cellular component
typical communication between cell
signalling cell produces extracellular signal molecule detected by target cell
target cell
have receptor proteins that recognize and respond to signal molecule and convert (signal transduction) to intracellular signaling molecules
cell signaling
signal reception and transduction (transmission from exterior to interior of cell)
examples of signal molecules
- proteins
- peptides
- amino acids
- nucleotides
- steroids
- fatty acid derivatives
- dissolved gases
types of signals (4)
- endocrine signaling –> broadcasting on radio
- paracrine signaling –> sending flyer to select people
- -> autocrine signaling –> writing reminder to yourself
- neuronal signaling –> phone call, long distance, but specific
- contact-dependent signaling –> in person
endocrine cells
cells that produce hormones
autocrine signaling
example of paracrine signal that respond to local mediators that they themselves produce
mating factor
small protein secreted when yeast cell ready to mate
is detected by the opposite sex as chemical mating call
neuronal signaling
neurons deliver message over long distance, but quickly and specifically to individual target cells.
neurotransmitter
an extracellular signal molecule from an electrical pulse from nerve terminal
paracrine signaling
diffuse signal molecule locally in the neighbourhood of the cell that produced signal
hormone
secreting signal molecule, into blood stream, broadcasting to entire body
contact dependent signaling
- intimate, short range communication
- no secreted molecule, instead direct physical contact of embedded receptor proteins
response to signal
- receptors only hear and respond to one type of signal, and are deaf to all other signals
- many receptors accept the same signal molecule, but is interpreted differently by target cells
types of extracellular signal molecules
- molecules too large or too hydrophilic to pass through membrane, use receptors on the surface of target cells
- molecules smaller, and more hydrophobic enough to pass into cytosol and bind to receptor proteins
- -> eg. steroid hormones; cortisol, estradiol, testosterone, thyroxine are hydrophobic that pass through membrane and bind to receptor proteins located in cytosol or nucleus
nuclear receptors
protein receptors located in nucleus or cytosol that are activated by signal molecules binding to the receptor which them changes the conformation
cortisol hormone example
cortisol hormone produced by adrenal gland crosses plasma membrane and binds to receptor protein which activates and enters nucleus through nuclear pore and binds to DNA and activates transcription of specific genes
ligand
a signal molecule, hormone
g-protein
protein attached to cytosolic side of membrane that binds to transmembrane protein that has changed conformation becomes activited and binds to enzyme that will change conformation and releasing another signal molecule cAMP (cyclic amp) that will elicit a cellular response
second messengers
cAMP, different molecules from the initial ligand that amplify and carry the same signal
phosphorylation cascade
when a signal molecule binds to protein that changes conformation and releases relay molecule, it interacts with intercellular proteins that exchange phosphate groups in a chain reaction, and then eventually reach the target cell, that will elicit a cellular response
receptor mediated endocytosis
- when bulk quantities of signal molecules are accepted by receptors
- the signal molecule as a substrate bind to the receptors that buds off into a vesicle along with any additional solute that enters
intercellular receptor
found in cytoplasm or nucleus, the signal molecule (ligand) must be able to pass through membrane, if small and non polar, and activate it
- can later enter nucleus and act as a transcription factor
types of cellular responses
- gene activation or inactivation (if icr enters nuclear)
- metabolic influence (activate enzyme that breaks down stored glycogen)
- initiation or halting of cell division
- -> malfunction can cause cancer, as regulates cell division
receptors
- either in membrane or inside of cell
- specifc ligands (substrates) that fit in the active sites
- will change conformation that will initiate cellular response
single pass receptor
is a cell surface receptor with one alpha helix transmembrane
- -> receptor tyrosin kinase
- -> protein tyrosin phosphate
- -> protein serine/thyreonine kinase
plasmodosmata
gap junctions where two plant cells overlap and send signal molecule (ligands)
intracellular signaling pathways
- relay signal onward
- amplify signal received to smaller messengers
- integrate multiple signaling pathways and relaying
- distribute signal to effector proteins that evoke cellular response
signaling by protein phosphorylation
phosphate covalently added by protein kinase that transfers terminal phoshate group from ATP to signaling protein
gtp binding protein
exchange gdp to gtp to recieve signal and switch back to gdp by hydrolyzing to release signal
gefs
guanine nucleotide exchange factors promote exchange of gdp for gtp by switching on gtp binding protein on.
gtpase activating proteins
stimulate hydrolysis of gtp to gdp switching off gtp binding protein off
three classes of cell surface receptors
- ion channel coupled receptors change permeability of membrane potential and produce electric current
g protein coupled receptors
activate membrane bound trimeric gtp binding proteins that activate enzyme or ion channel in membrane
