BIOL 2020 Lecture Notes - Lecture 7: Conformational Change, Cytosol, Intermediate Filament
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Cytoskeleton and Cell Motility
o Cyto=cytoplasm
o Skeleton (that is self explanatory)
o In eukaryotic cells, consist of filaments and tubules like structures within the cytosol
of cell
o There are three different elements
o Microtubules
o Microfilaments
o Intermediate filaments
o These are all structures called polymers, we call them this because they are built up of
globular proteins hooked together one after another (monomers)
o Linkages are non-covalent
o Each of these is formed from a protein or a group of proteins
o Microtubules (tubulin)
o Microfilaments (Actin)
o Intermediate filaments (several related proteins, these are called intermediate
filament proteins)
o Rapid assembly and disassembly of these within the cell because the bonds are non-
covalent
o Highly dynamic
o Cytoskeleton involved in displacement and movement of materials/organelles in the
cell
o Mitosis and cell division
o Epithelial cells - cell that lines your gut until excreted, so it is fairly stable in its
location. It is highly specialized to absorb nutrients
o Intermediate filaments - involved in structure and support
o Read - techniques for the stud of the cytoskeleton (pg. 326-330)
o Like a garden hose, it is tubular and hollow in the middle
o Remember that they are about 24-25nm in diameter
o Tubules are made up of protofilaments - in the image they are the columns of circles
(almost always 13)
o Each protofilament is composed of a globular protein (tubulin) and tubulin is a
heterodimer, meaning that there are two different subunits that make up the one
protein
o They are called alpha and beta tubulin - encoded by different genes and come
together as a heterodimer to give a functional tubulin
o The ribbon diagrams show the difference between alpha and bata tubulin
o They are both GTP binding proteins
o When alpha tubulin binds GTP, it doesn’t hydrolyze or leave the alpha, so it is
called the non-exchangeable GTP. It will always stay bound to the alpha tubulin
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