life at extremes Flashcards
how are cells dynamic
not static
active
can respond to their environments
define robustness
the ability of a cell to maintain performance and function in the face of internal and external disruptions
how does fever during infection help the mmune system?
increased white blood cell movement
increased proliferation of T cells/WBC
enhanced rate of phagocytosis
what happens to cells at high tempertures eg above 37
they get stressed
enzymes cant work properly.denatured
proteins dont fold properly
membrane more fluid
what is the consequence of an ill-folded protein?
faulty protein
loss of regulatory component
loss of control of the protein
what happens to membranes as they become too hot?
hard to control movement
too fluid
what does the membrane do if it becomes too hot?
change the lipid composition to being fully saturated
cholestrol added
what does a fully saturated lipid membrane mean>
single bonds only
most viscous
compact
less permeable
what does cholesterol do to membranes?
adds strength and stabilises the membrane
how is the issue of proteins not folding properly fixed?
heat shock proteins
what is a heat shock proteins?
produced when the cell is exposed to elevated, sub-lethal temperatures
what is the function of a heat shock protein?
help proteins fold properly
they bind to proteins that are newly synthesied and hold them in place for binding
what issues are caused by low temperatures
slow enzyme reactions
rigid and viscous membranes
ice crystals making holes in membranes
how does the membrane respond to being too cold
unsaturate the lipids making them have double bonds
this makes the membrane more fluid
cholesterol is removed and the membrane made less stable and more fluid
what is the function of glycoproteins and glycolipids
protect the cell
stablise protein structures in ECM
buffer
how are glycolipids and gycoproteins produced?
carbohydrates are added to proteins in the RER
glycosidic bonds link these to the side chains of amino acids
flags the protein to be moved to membrane
how can ice crystals be bad?
kill the cell by punching holes in the membrane
How do artic fish prevent ice crystals forming?
glycoproteins in blood arrange the formation of the crystals so they form along protein making them harmless to cells
what’s special about the wood frog?
can freeze solid and thaw out multiple times and be fine
antifreeze glycopoteins and high gluose levels help them
how can bacteria survive extreme temperatures
proteins and metabolism in some mean they can be optimised for cold temps
their proteins are flexible and only work at the certain temperature ranges
what is chitin
structural carbohydrate used with other substances to create a harder material
whats wrong with low oxygen?
essential in ATP synthesis
low oxygen is toxic
death via necrosis
what oxygen do cells like?
low oxygen
as you get further from blood vessels, nutrients and oxygen decrease anyway
what is hypoxia
and environment low in oxygen
high altitude
aquatic
when can hypoxia occur?
premature babies
poisoning
anaemia
what is local hypoxia
ischaemiea strokes
cancer and vessels collapse
how do cells sense hypoxia?
special oxygen sensing enzymes
how do oxygen sensing enzymes work?
they activate a range of transcriptional factors
stop cell cycle after G1
stop things that arent essential
switch to anaerobic respiration
what is angiogenesis?
making new blood vessels
how does angiogenesis occur?
in response to hypoxia cells activate genes
cells are stimulated in vessles to branch off, proliferate and move towards hypoxic cells
what causes the cells to proliferate in angiogenesis?
genes involved in growth factors such as VEGF and FGF
what is VEGF?
vascular endothelial growth factor
how do cancer cells exploit angiogenesis?
they are high demand cells and use energy quickly
they send out growth signals that act on nearby vessels
the vessels send off shoots towards the tumour in all directions and the tumour ends up with an extensive blood supply helping it grow
what is quiescence?
state of reversible cell cycle arrest
what happens in quiescence?
stay in G0 phase
starvation of the cell
low metabolic rates
non-essential things are shutdown
what is irreversible cell cycle arrest called?
senescent
what is autophagy
Self-eating
protective mechanism
how does autophagy work?
cells form membrane vesicles called autophagosomes
to digest organelles and proteins with enzymes
why is autophagy used?
efficient method to recycle building blocks in times of nutrient deprivation
example of a small scale autophagy?
proteasome
what does a proteasome do?
recycle individual proteins and amino acids for more protein synthesis
examples of toxic environments for cells
raidation, UV light
free radicals and oxidative stress
toxins and posions
how is a reactive oxygen species made
last step in transferring electrons to oxygen doesnt happen
creates highly reactive oxygen species
made in cells as side effect of normal metabolism
what can reactive oxygen species do to cells?
react with biological molecules
chain reaction of macromolecules creating more radicals
modify proteins
what effect can ROS have on proteins?
modify structure and function
crosslink or fragment them
modify nucleotides
how can you prevent ROS damage?
antioxidants
how do antioxidants prevent reactive oxygen species damage
react with them and neutralise them
an example of natural antioxidant in the body
glutathione
found in the liver
donates electrons to ROS to make them more stable
what is superoxide?
converts superoxide to hydrogen peroxide
then catlase converts that to water
line of defence to help
whats a drug transporter?
transmembrane protien using ATP to transport drugs and substances across membranes
the purpose of drug transporters?
stops exposure to chemicals
gets things out of cells before they cause damage
transports small dangerous chemicals they dont like
what is the DNA damage response mechanism?
detection
cell cycle stops
repair initiated, genes turned on
if damage extensive cell undergoes apoptosis
list some things damaging dna
cellular metabolism UV light ionising radiation chemical exposure replication errors
what is the integrated stress response?
series of mechanisms to protect the cell and fluctuations in the environment
what are the cells defences?
antioxidants
DNA repair
apoptosis
ECM
