cell signalling Flashcards
why do cells need to respond to their environment?
- respond to their environment
- survive and communicate
when did cell signals become a thing?
early history of life
as life became more complicated, so did signals
what do most cell communicate through?
chemicals:
hormones
growth factors
inhibition
what do cells respond to
temp
osmosis
stress
nutrients
how do batceria/ prokaryotes respond to signals
moving towards or away from the signal using flagella for motion
spinning of the flagella causes the bacteria to move direction
how can bacteria respond to the new signals
synthesise new proteins to optimise survival
activate gene expression to make new enzymes
how do yeast respond to each other and partneres
exchange of chemicals to find partners
mting factors are short peptides about 12 amino acids
secreted into environment
yeast move along concentration gradient to bind in mating
two different mating factors based on sexes to give two genotypes
what allows yeast to become diploid durin mating?
two diffferent mating factors of genotypes allow sex and diploid mating
what signals so multicellular organisms respond to?
phyical and environmental presence of other cells
where they are, right or wrong
what makes multicullular cells stay alive
being in the correct place means they get correct signals and can stay alive
how does place impact cells
the matrix cells are in will contain proteins to tell them they are in the correct place and can survive
different tissues make differing growth factors for cells to bind to
what makes cancer cells different?
they no longer respect environmental signals
dont need signal for growth or death
become independent through mutations
types of stimuli for cells
growth factors matric contact hormones light photons cell to cell contact odorants, smell and taste touch temperature
what is signal transduction
mechanism by which a cell is able to respond or adapt to changes in the envirnment
how are extran stimuli converte to cellular responses?
cell juctions cell-cel recognition paracrine synapses endocrine
how do cell junctions work for communication
exhcange of ions and small molecule through pores between close cells
protein pores allow adjacent cels to communicate or use ion channels too
what type of cell junctions are there?
in animal cells: gap junctions
in plant cells: plasmodesmata
how does cell-cell recognition work for communication?
two cells can recognise each other and their context through surface receptors
this type of signalling is for survival and to tell cells they are in the correct place
how is paracrine signalling used
occurs locally
growth factors for example made and secreted by transmitting cells
diffuse locally until they encounter target cells with correct receptors
how do the paracrine signal fators work
growth factors for example made and secreted by transmitting cells
diffuse locally until they encounter target cells with correct receptors
factor creates a concentration gradient telling the cell how close or far it is from the signals by how much they recieve
how does synaptic signals work
specialised form is paracrine signals
highly directional compared to normal paracrine
what is endocrine and hormone signalling
long distance signals that use the blood system to transport sigals throught the whole body to reach targets
difference between paracrine and endocrine
paracrine uses blood stream and has a wide effect
paracrine si very localised
steps of the signal transduction pathway
receptor on surface –> signals in cell –> response
three phases of cell signalling
- reception or recognition
- tranduction
- response
process of cell signalling reception/ recognition
target cells detect signal from outside
chemical binds to protein on cellular surface
what is a ligand
external stimuli that binds to a receptor
its a first messenger
how does transduction occur in cell signalling
converts one type of signal into another ( the initial stimulus or ligand binding) into another signal such as internal signal or second messengers.
how are cell signals amplified?
enzymes
types of receptors
ion channel-linked
G-protein linked
enzyme linked
what is a G-protein linked receptor
loops inside and outside the membrane to connect with ligands or other proteins inside the cell
how do tyrosine-kinase receptors work
- resting in cell, unstimulated
- receptor binds ligand and becomes activated
- recruits different effectors to propagate the signal further into the cell
explain dimerisation using tryosine kinase receptors
- when ligand binds it changes shape of molecules
- enzymatic part phosphorylates tyrosin
- leads to activation of proteins in a bindin equence leading to cellular response
- tyrosin phosphylates shows receptor is activated,
- proteins can now bind
what is an effector
enzymes in the cell that transduce ligand actavated signals into the cell
catalyse the formation of second messenger moelcules
whats a second messenger molecule
small chemical that act as messengers
carry signals from one part of the cell to another through diffusion
what is ras-MAP
common growth factor for activating signalling pathways
regulates changes of gene expression and cell cycle
activation of this pathway is linked to many cancers
describe a simple signalling cascade
ligand, first messenger cell surface receptor effector enzyme, second mesenger amplifiers target response proteins
what are the key concepts in cell signals
the process is highly specific and organised
molecular switches are used
cascade amplifies the signal
what is molecular recognition?
ligand- receptor interaction determines specificity of the signalling
lock and key fit of the ligands fitting the receptor
molecular switches
receptor phosphorylation leading to signalling molecules binding and activation is a switch
how are signals amplified?
receptors when activated activate transducers and continue till negative feedback. these can modify cell behaviour.
why is amplification used?
more efficient
ways signals are amplified
- ion channels
- chain enzymes in series
how do chain enzymes in series work
amplification at each step in the series causes more proteins to be activated
much more efficient process
what response can a cell have from a signal?
secretions into environment change in cytoskelton change in function move the cell change gene expression metabolism aactivation/inhibition of pathways activation of certain genes
what is a target response protein
something that brings about the change in the celll
signal component at the end of the pathway
