BICD 110 Lecture Notes - Lecture 10: Phagocytosis, Phagosome, Filamin
28 Jun 2018
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BICD110 Lecture 10 Notes 5/8/18
- The cytoskeleton: can be rigid or dynamic
oKeratocytes: skin cells on scales of fish. They can move rapidly to heal scratches
- Cytoskeletons of the eukaryotic cell
o3 major types of filaments make up
the cytoskeleton
microfilaments: actin
microtubules: alpha/beta-
tubulin dimer
intermediate filaments: various
- Overview of actin
oHighly conserved, 43 kDa, 5% of cell protein, can exist as a monomer or polymer
oeach actin binds an ATP
oin the cell, actin polymerizes into microfilaments/long polymers. There’s a (-) and (+)
end, and actin monomers get added at the (+) end
ohas double helical structure. Rarely found as a single filament; instead, found in bundles
or networks
- Actin forms many important structures: these vary with cell type, so cells
can perform different functions
oActin bundles: found in microvilli, adherens belt, filopodia, stress
fibers, and contractile ring
Can be non-contractile: filaments crosslinked by fimbrin (short
crosslinking protein) to keep filaments straight and parallel. (+)
ends at one side and (-) ends at other side of cell. Filaments stay attached to
PM through lateral sidearm created by myosin I, allowing permanent
structure. Myosin II can’t fit in between filaments, so can’t contract
Ex: microvilli
oFound on epithelial cells of kidney or gut
oIncreases SA of PM for absorption
oFairly permanent structures
oAlso found on cells of inner ear (stereocilia that sense sound)
Stereocilia contain mechanically-gated channels that are bent by sound
waves. Bending pulls open channel on adjacent stereocilium, allowing K+
to flow in. Perceived as sound. Can break if sound wave too large
Can be contractile: filaments lined up anti-parallel to each other, joined
together using alpha-actinin (long crosslinking protein). Long crosslinker
allows myosin II to go in between filaments, allowing contractions to occur
Ex: Contractile ring
oUsed to divide cells in cytokinesis at the end of mitosis
oRing is a contractile actin bundle that
contains actin filaments and Myosin II
molecules
find more resources at oneclass.com
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Document Summary
The cytoskeleton: can be rigid or dynamic: keratocytes: skin cells on scales of fish. Cytoskeletons of the eukaryotic cell: 3 major types of filaments make up the cytoskeleton. Microtubules: alpha/beta- tubulin dimer intermediate filaments: various. Overview of actin: highly conserved, 43 kda, 5% of cell protein, can exist as a monomer or polymer, each actin binds an atp, in the cell, actin polymerizes into microfilaments/long polymers. There"s a (-) and (+) end, and actin monomers get added at the (+) end: has double helical structure. Rarely found as a single filament; instead, found in bundles or networks. Actin forms many important structures: these vary with cell type, so cells can perform different functions: actin bundles: found in microvilli, adherens belt, filopodia, stress fibers, and contractile ring. Can be non-contractile: filaments crosslinked by fimbrin (short crosslinking protein) to keep filaments straight and parallel. ends at one side and (-) ends at other side of cell.
