Endocytosis
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- Created by: Sarah
- Created on: 16-05-17 20:32
how do cells take up materials from the extracellular environment?
endocytosis
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when can recycling occur back to the cell surface happen?
early endosomes and late endosome
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what is taken up in endocytosis?
enzymes, viruses, bac, membrane, signals, nutrients, antibodies, morphogens growth hormones
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how does iron get into cells?
trasferrin
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how do babies in the womb get Igg?
by endocytosis
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what were used as tools for endocytosis?
viruses used electron microscopy
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what allows the selection of macromolecules for endocytosis?
clathirin coats
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what happens to regions of uptake?
become invaginated (more curved) and pinch off forming vesicle
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what needs to be lost to expose snares?
coat
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what are the 4 different fates of endocytosed material
1) degradation 2) storage 3) transcytosis 4) recycled
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example of storage?
hens egg takes up nutrients
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what is trancytosis?
move across cells like epithelium
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example of trancytosis?
Igg in womb
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2 types of endocytosis?
phagocytosis, pinocytosis
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what does it have to be to be phagocytosis?
eating bigger than 0.5um, into vacuole
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what is pinocytosis?
cell drinking less than 0.5um into vesicle
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hw does macrophage engulf rbc?
completely encapsyulate by using pseudopods
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what is the movement of he phagocytes membrane by formation of pseudopods?
actin dependent
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what is frustrated phagocytosis?
2 mscrophages try to engulf bacteria but nether can
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what does frustrated phagocytosis tell us?
tells you the fusion event cell autonomous is particular for a particular cell, knows that other mac is a different m to bac
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wha did they do with macrophages and latex beads?
measure latex bead, feed mac latex bead, can count number of beads other time can work out how much m in each time
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how much of the totl surface area internalised per hour?
30%
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what was there no change inn? what does this tells us?
no change in cell size therefore M must be recycled
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why do we use LDL protein?
brown and dalton, looked at hyporcholestrimia
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what was one of the reasons you have hypocholestrimia?
defects in LDL metabolism
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what does LDL do?
big particle, transports cholesterol in serum
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when cells need cholesterol what is the first response?
synthesis LDL receptors, try to take up LDL from diet
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what is the structure of LDL rec?
TM domain to anchored, cyto domain interact with peripheral m proteins, Extracellular domain to bind LDL
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advantage of rec?
even if ldl low abundance high affinity rec scoops up any
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what happens with LDL endocytosis?
LDL binds to rec, recs cluster in clathirin coated pit,, lattice like coat, clathirin is peripheral m, coated pit invaginated ->coated vesicle->coat lost for snares->vesicle fuses with early endosome(red ph)
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what is he ph of the early endosome?
ph 6.5
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different ph does what to the rec?
the rec and ligand dissociates
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where does LDL go from early endosome?
to lysosome where hydrolytic enzymes break down into cholesterol
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what happens to the ldl receptor?
tubular parts of early endosome -> back to m, recycled
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how many times do the ldl rec recycle?
60 times
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how did they show ldl receptors are being recycled?
stopped protein syn but endocytosis carried on
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what is red ph for?
cargo sorting to correct destination, targetting to lysosomes
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what is there a gradient of in the endocytic pathway?
ph- it decreases
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what is Ras?
a GTPase, important in signlalling
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what is rab?
related to ras family
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what do GTPases act as?
moleculear switches, GTP-on GDP-off, do membrane trafficking
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where is ras on (GTP)?
when its on the m
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what is between early endosomes and lysosomes?
late endosome
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why is it called early and late endosomes?
how long it takes matrial to get there
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what are late endosomes full of?
multivesicular bodies
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what are mutlivesicular bodies?
endosomal membrane invaginates forms lots of vesicles
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what are multivesicular bodies important for?
turning off switches/signals
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what are multivesicular bodies other name?
intra lumenal vesicles
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what can you stain lysosomes with
acid phosphatase
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how is it easy to purify clathirin?
freeze fracture
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what do we know less about the pathway?
its regulation
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clathirin is one of the ways cargo gets into cells whats others?
macropinocytosis, noncoated outs, caveolae, phagocytosis
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how does macropinocytosis work?
similar pro+machinery to phagocytosis, IS,dendritic cells form ruffles that fold back onto themselves, no selective method
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what shapes are clathirin coated pits and vesicles made of?
hexagons and pentagons structures from clathirin pro
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what does clathirin triskelia polymerise into?
lattices
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where are light chains in clathirin?
light chains near hub of triskelia, much smaller
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how did they understand how clathirin works?
take purified clathirin in vitro it can form structures similar to coated vesicles
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what does clathirin do?
provided structural scaffold for cargo
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what adaptin molecules do?
select cargo and link it to clathirin as it doesnt bind clathirin directly
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size of coated ut?
200um
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a hens oocte have adapted coated pits how? why?
made larger, store lots of stuff in eggs so can undergo lots of division after fertilisation
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what does dynamin do?
the scission of coated pits+vesiicles
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what is dynamin?
is a large GTPase, pinches off coated pit and makes it coated vesicle
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Other cards in this set
Card 2
Front
when can recycling occur back to the cell surface happen?
Back
early endosomes and late endosome
Card 3
Front
what is taken up in endocytosis?
Back
Card 4
Front
how does iron get into cells?
Back
Card 5
Front
how do babies in the womb get Igg?
Back
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