Homeostasis Flashcards
why does phased seperation occur
contact is minimised between polar and non-polar components by grouping polar together so they can have as many polar interactions as possible
why does phased separation occur
contact is minimised between polar and non-polar components by grouping polar together so they can have as many polar interactions as possible
what is added to the phospholipid bilayer to prevent it freezing at body temperature
cholesterol
which kind of molecules cannot cross the lipid bilayer
hydrophilic
examples of what can pass through the phospholipid bilayer
CO2, steroids (testosterone), some drugs
4 types of diffusion transport
direct free diffusion
uniporter
co-transporter
antiporter
where are high sodium levels found? where are high potassium levels found?
sodium - outside cell
potassium - inside cell
what does the Na+/K+ ATPase do
3Na+ out, 2K+ in
example on how the NA+/K+ ATPase can be used
lower concentrations of Na+ in cell cause it to diffuse in through other receptors, providing energy for eg glucose to enter with it
4 classifications of paths?
autocrine
juxtacrine
paracrine
endocrine
autocrine?
signalling to itself
signalling in general to another cell
paracrine
juxtacrine
signalling to an immediate neighbour
endcrine?
passing via blood to otherc ells
are steroids hydrophobic or hydrophilic
hydrophobic
how do steroid signals alter gene expression?
pass through lipid bilayer, bind to transcription factor, affects transcription of DNA
what are steroids generally used for? examples?
long term things:
sex determination
menstrual cycles and puberty
stress
inflammation
etc
signals which cannot pass through the cell membrane (too hydrophilic)
neurotransmitters, peptide hormones
two ways hydrophilic signalling molecules pass on their signals into the cell?
binds to receptor causing conformational change
dimerization - each half of signal holds together two receptors which act on each other if held together long enough
G-protein signalling? - example for calcium
G-protein coupled receptor activates, binds G-protein which is activated then can activate another enzyme - phospholipase, which breaks many phospholipids (amplification) which bind to calcium channels in the ER releasing Ca2+ down conc gradient and calcium activates various proteins
how can calcium blood concentration levels be raised
PTH from parathyroid gland causes reabsorption from urine and reabsorption called bone.
integral control?
how far wrong something is and for how long - more and more active the longer something is in error
proportional control?
looks at how far wrong something is
differential control?
how quickly things are changing
