module 5 (4) Flashcards
(16 cards)
define negative feedback
work to reverse changes and restore conditions to their base level
how does positive feedback happen
effectors are stimulated to reinforce a change and increase the response
> blood clotting cascade
what do homeostatic changes depend on
exothermic chem reactions
latent heat of vaporisation
radiation
convection (heating or cooling by currents)
conduction (heating as a result of particle collision)
what happens in vasodilation
shunt vessel constrict
forces blood through capillary networks close to the surface of the skin
what are some adaptations for cold climates
minimised SA:V (small ears) reduce cooling
thick insulating layer of fat
hibernation
what is the heat loss centre
activated when blood temp increases
sends AP through autonomic to skin and muscles
what is the heat gain centre
activated when blood temp decreases
sends AP through autonomic to skin and muscles
how does rejection work
antigens on donor organ different to antigens on body cells (self)
immune system recognises the antigens as foreign and attacks
how do we produce heterochromatin
make histones more positive
by methylation
how do we produce euchromatin
make histones less positive
by acetylation or phosphorylation
what is the lac operon
group of inducible genes
group meaning, more than 1 gene is under control of the same regulatory sequence
where does the polymerase bind to in the lac operon
promoter region
when there is glucose, what is the levels of lac genes transcribed
none
in high levels of glucose, what is the level of CAP protein
more glucose
less cAMP
less CAP
less transcription
if there is no lactose and no glucose, what is the level of transcription
none
repressor still binded to operator
so no transcription even if CAP is present
in low levels of glucose, what is the level of the CAP protein
less glucose
more cAMP
more CAP
more transcrption
