Signalling Flashcards
what are some examples of cell signals?
oxygen supply, temperature, pathogens, hormones, growth factors
why is cell co ordination important during development?
to ensure cells end up in the correct places
morphogen?
molecules secreted from one cell which diffuse out and create a conc gradient. target cells in different positions along conc gradients have different developmental fates depending on the conc of morthogen they receive
how is blood glucose levels an example of cell signalling to maintain homeostasis?
high blood sugar - insulin released and glucose taken into cells and stored and glycogen
low blood sugar- glycogen turned back into glucose in the liver and released into the bloodstream
what are some examples of diseases caused by normal signalling pathways?
diabetes and cancer
what are the different types of signalling?
physical, electrical
and biochemical
what are some examples of physical signals?
pressure or temperature
what are the classes of range of action?
endocrine
paracrine
juxtacrine
autocrine
what are the 3 common stages for all signals?
detection, transduction and response
detection
signal/stimuli
transduce
the signal from the site of detection to the part of the cell that will respond
respond
must be coordinated with responses to other signals; and with responses of other cells
what are some examples of intracellular receptors?
hydrophobic signal molecules can diffuse through plasma membrane into the cell eg steroid hormone, nitric oxide
how do steroid hormones work?
they bind directly to intracellular receptor proteins and hormone receptor complexes act as a transcription factor. the complex binds to DNA and alters gene expression
what are some examples of cell surface receptors?
water soluble signalling molecules must use a cell surface receptor protein eg insulin, adrenaline
how do surface cell receptors work?
the hormone binds to the receptor and it becomes activated and the shape/activity becomes altered which creates a cellular response intracellularly
what are the 3 types of cell surface receptors?
- ion channel linked
-G protein linked - Enzyme linked
ion channel linked receptors
neurotransmitter binds to receptor causing an ion channel to open. flow into cell changes electrical properties of cell.
G protein coupled receptor
eg Adrenaline, seratonin, glucagon. the activated G protein activates enzymes that passes on signal into cell.
ligand bids -> conformational change in cytoplasm domain -> allows G protein to bind/be activated by receptor -> activated G protein activates intracellular enzymes
enzyme linked receptors
eg many growth factors, insulin. when a signal binds to the inactive receptor it brings the two parts of the receptor together which causes activation of enzyme activity within the cell.
what are kinases
enzymes that phosphorylate
what are phosphatases?
dephosphorylate
what is amplification?
when one receptor molecule activates many relay molecules. different receptors use different transducers/amplifiers
what are enzymatic cascades?
often activated in response to growth factor RTK activation.
relay proteins Grb/Sos activate RAS (a proto oncogene commonly mutated in cancer)
Was activates a MAP kinase cascade
what are second messegers?
a small molecule produced in large amounts inside cell after reception activation eg cAMP. Second messenger coordinates cell response
how is adrenaline transduced?
second messengers
GPCR > cAMP>PKA activation>effector proteins phosphorylated
what are some of the molecular level responses?
changes in gene expression, protein activity, protein binding, protein localisation
what are G-protein coupled receptors
have 7 domains
what are some examples of the effects of adrenaline?
different tissue specific responses
-glucose released from skeletal muscle, liver
-increased heart rate
-vasodilation of some blood vessels, constriction of some others
Which molecule would participate in the transduction stage?
BRAF
Which molecule would participate in the reception stage?
VEGF receptor
Which signalling molecule binds to an enzyme linked cell surface receptor?
EGF
what is signal transduction?
when various processes occur within the second cell to conduct the signal to the correct parts of the cell and initiate the correct response
what is integration (of signal response)?
when multiple signals work together to produce an overall cellular response
what is cyclopia?
a failure of a signalling pathway called the sonic hedgehog signalling pathway . If it goes wrong you get a failure of proper development and separation of the two halves of the brain and the eyes.
what are the 2 types of biochemical signals?
-classifications based on chemical structure
-classification by the distance over which they act
what does salbutamol target?
beta 2 receptor (cell surface)
endocrine?
signal that acts over a long distance (transported via bloodstream) is termed endocrine
paracrine?
releasing a signal to act on a nearby cells (signal molecule moves by diffusion)
juxtacrine?
signal that acts on a neighbouring cell via cell to cell contact
autocrine?
a signal that acts on the same cell that releases it.
what kind of molecules are intracellular signallers?
hydrophobic or gases to plass plasma membrane
what are the 3 stages of signal transduction?
-reception
-transduction
-response
what is the MAPK cascade?
mitogen activated protein kinases
what kind of signallers are oestrogen and testosterone?
hydrophobic hormones.
what is cAMP?
second messenger produced by enzyme adenylyl cyclase
which enzyme is responsible for breaking down cAMP?
phosphodiesterase
what is an example of an ion channel receptor?
nicotinic acetylcholine receptor
what is an example of a G protein coupled receptor?
Muscarinic acetylcholine receptor
adrenaline
what is an example of an enzyme like receptor?
VEGF
