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Notes taken during lecture

Course Code
Jean Jiang Nash

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how cells interact to form complex 3d shapes?
Loss of control cell tumours form proliferate too much change from benign to
metastatic tumour
For the exam, responsible for material in the TEXTBOOK AND THE LECTURES
Find what was covered in lecture in the readings, and make sure this is know
Before coming into lecture, read the captions of the figures in the readings
figure out what they mean
Cytoskeletal machinery
Goblet cell specialized shape, structure, filled with vesicles containing mucus
that is secreted from cell
oShape depends on cytoskeleton, which allowed the cell to specialize
Sperms cytoskeleton allows it to specialized into swimming
Rod cell has membrane folding apparatus at top that capture photons
oPhoton information can come out of the synactic region at the end of the
oDue to the cytoskeleton, attachment between cytoskeleton and the
membrane allowing cells to have different functions
Microtubules attached to chromosomes, during mitosis separate chromosomes
Make sure segregate evenly into two cells
Cell-cell interactions reason behind tissue strength
Proteins embedded in plasma membrane can be pulled out hydrophobic interactions not
very strong
But inside the cell, the proteins sticking cells together are attached to cables
Blue part is the cell attachments adhesion complexes
Intermediate filaments in green
oInside the cell
oBut attached to adjacent cell huge protein interaction network, making
this entire thing into a strong tissue
oBecause of these intermediate filaments, skin is supple, can be deformed
but not broken
Lot of dynamnics in cell must be regulated
Cytoskeleton can be very dynamic and is highly regulated
Can migrate if it must
Acting like cables for
oVesicles moving on cables,
oFilaments have polarity so movement can be in one direction or other
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Polarized cable network, so vesicles can move towards plus or minus
oHighly regulated
Acting like poles
oDeform cell surface
oParallel actin microfilaments deforming membrane to form microvillus
to increase apical SA, so absorb more efficiently from lumen of intestine
Strong generalization made up of components microfilaments, microtubules
oMade up of subunits that allows for regulation to be taken apart in
one part of cell, move it and reassemble it somewhere else
oAllowing for movement and dynamics
oAllows fast assembly and disassembly of cytoskeletal networks
Formed from actin monomers
Smallest ones
Formed from tubulin monomers
Big ones
Intermediate filaments
Intermediate sized ones
Ex. keratin in hair, nails, skin
Generalize how filaments form
Rate limiting step is filament nucleation
oNot nucleus of cell, but small cluster of monomers
oTo be added to end, so can grow
But are unstable
oSo fall apart
If these oligomers are stabilized, then long polymers can be nucleated
Regulation by regulatory proteins
Nucleation is slow without regulatory protein
Nucleation can occur with just monomers in test tube very inefficient
unacceptable in a cell
Microfilament assembly without regulatory proteins
K on tendency of a subunit to bind
K off tendency of a subunit to dissociate or release
Dont worry about the chemistry or the calculation
Multiplied by the concentration of free monomers
oDoesnt matter how much the monomers want to bind if none are present
oLow concentration, frequency decrease
oK on times concentration of free monomers
K off
oLoss does not depend on free subunit concentration
As for the other end, it depends on the filament type
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