Lecture 6: exocytosis, endocytosis, plasma memb and lysosomes Flashcards
what component only exists on extracellular side of memb
glycolipids
what type of phospolipid acts as a signal for phagocytosis
phosphatidyl serine
how does an a helix allow hydrophobic interactions with the bilayer
hydrophobic AAs go on the outside
how do beta barrel proteins give evidence for endosymbiotic theory
cuz they’re in bacteria
but also mt and cp
so it shows they are derived from bacteria
3 ways proteins can be associated with the membrane
amphipathic helic
convalently attached lipid anchor
peripheral membrane protein
what are the 2 routes for vesicles coming off the golgi and fusing w/ plama memb
- constitutive
- regulated
what does constitutive secretion allow
plasma membrane growth by supplying memb proteins and lipids
and protein secretion (e.g. insulin, ‘dead’ proteins)
examples of cargo transported by regulated secretion
hormones, mucus, digestive enzymes, neurotrans
example of signal that can induce regulated exocytosis
hormone
neurotrans
Ca2+
is regulated or secretory faster
regulated
secretory takes time, gotta make proteins etc.
3 main forms of endocytosis
phagocytosis
pinocytosis
receptor mediated endocytosis
what organisms takes up food via phagocytosis
protozoa
how is the microbe destroyed in the phagosome
fuses with lysosome
what organism has found a defense against phagocytosis and how
mycobacterium tuberculosis
inhibits membrane fusion between phagosomes and lysosomes => multiplies in macrophages
how is pinocytosis different
non selective
takes in mini vesicles of fluid from out to inside
what is pinocytosis mediated by
clathrin coated vesicles
how is Receptor mediated endocytosis beneficial
selective uptake of molecules
increases efficiency of uptake up to 1000 fold
example of something that gets take up by Receptor mediated endocytosis
LDL
binds to LDL receptors on cells
and internalised by clathrin coated vesicles
what happens in endosomes
has acidic pH
LDL dissociates from the receptor
and receptors go to plasma memb
other examples of things taken up by receptor mediated endocytosis
Essential metabolites
Vitamin B12, iron
Signalling molecules
Epidermal growth factor (EGF)
Virus particles
Influenza, HIV, coronaviruses
3 possible fates of receptor proteins after endocytosis
most recycled
some degraded
or transcytosis
why are lysosomal enzymes not dangerous if they leak out into cytosol
active at ph %
what is the acidic pH in lysosomes actively maintained by
atp dependent proton pump
what are lysosomal enzymes modified by
mannose-6-phosphate
this occurs at the golgi
