maintaining body structures (W10) Flashcards
what is pausing in the cell cycle regulated by
CDKs (cell dependant kinases) - relieve breaks in cycle
what external signals control CDKs
mitogens
examples of mitogens
PDGF - platelet-derived growth factor
EGF - epidermal growth factor
erythropoietin
what are growth factors
extracellular signal proteins which stimulate cell growth (increase in cell mass)
how do growth factors work
promote synthesis of proteins and other macromolecules and inhibit their degredation
example of factor that inhibits growth? specific function?
myostatin (specifically inhibits growth of myoblasts - muscle precursors)
what factors regulate cell death
survival/death factors
motor neuron production in embryonic stage?
increase in first half (survival factor independent), decrease in second half (survival factor dependant)
cancer cells relation with growth control mechanisms and survival signals? Why could this be significant?
lost normal growth control mechanisms but may retain dependency on survival signals. Therefore suppressing survival signals could potentially be used to combat cancer
mechanisms of organ/tissue growth? (mouse experiment)
remove spleen from mouse and add different numbers of foetal spleens will result in the same overall size of spleen (extrinsic mechanism)
if you do the same with thymus glands they grow to normal size (intrinsic mechanism)
is there a universal mechanism for organ growth?
NO!!!!
where are stem cells located in the small intestine?
crypts
name for rapidly dividing cells in crypt of small intestine
transit amplifying cells
2 mechanisms of stem cell renewal?
asymmetric division
independent choice (determined by environmental factors)
what are intestinal stem cells influenced by
signals from Paneth cells and connective tissue surrounding crypt
what is WNT?
secreted signalling molecule
what is Apc?
inhibitory component of WNT pathway
what effect does the absence of WNT have on Apc
in the absence of WNT, Apc degrades beta-catenin
what effect does the presence of WNT have on Apc
In the presence of WNT, Apc is inhibited
what is beta-catenin? what is its function
transcriptional factor.
drives proliferation and stem cell state
where is WNT produced and secreted
Paneth cells
which cells have WNT receptors
intestinal stem cells
WNT pathway summarised?
Paneth cells produce & secrete WNT
WNT receptors on stem cells recieve WNT & inhibit Apc
Apc can’t degrade beta-catenin
beta-catenin translocated to nucleus & causes proliferation & stem cell state
causes of cell death
mutation (external causes eg radiation, or spontaneous DNA damage, replication errors)
DNA repair declines with age
mitochondrial damage (less ATP)
damage macromolecules (proteins, DNA)
Shrinking telomeres (protective cap on chromosomes, if not working causes DNA damage)
infection/trauma
