Chapter 17 – cytoskeleton
Cytoskeleton; network of protein filaments in the cytoplasm.
Support large volume of cytoplasm
Responsible for large-scale movements
Controls the location of organelles and provides the machinery for transport
between them
Segregation of chromosomes into 2 daughter cells at cell division
Cytoskeleton consist of;
Intermediate filaments; structural elements crossing the cell. Go from one side
of the cell to other side. They determine the shape of the cell. Desmosomes
have on their side’s intermediate filaments. provide cell with mechanical
strength
Microtubules; Have a center from which they originate and stretch out through
the cell enable cells to move (sperm)
Actin filaments; organized around the cell membrane. muscle
contract/movment
Intermediate
filaments fibrous protein subunits
They bind via desmosomes.
They are also found in the nucleus of eukaryotic cell
nuclear lamina, underlies nuclear envelope
They prevent rupture. When a cell stretches and there is
intermediate filament in it cells stretch but don’t break they
remain intact and together
Strong and ropelike
They are ropelike strands. Self-assembly proteins
1. They have a N-terminus and C-terminus; alfa-
helix region of monomer
2. Coiled-coil dimer
3. Staggered tetramer of two coiled-coil dimers
4. Two tetramers packed together end-to-end
8 tetramers
5. Eight tetramers twisted into a ropelike
filament
All the interactions between the filaments depend on noncovalent bonding
Strengthen cell against mechanical stress
They have different names in cytoplasmic and in nuclear
Cytoplasmic
o Keratins; in epithelia
, o Vimentin and vimentin-related; in connective tissue, muscle cells and
neuroglial cells
o Neurofilaments; in nerve cells
Nuclear
o Nuclear lamina; in all animal cells
Accesory (aanvullend) protein (plectin) cross link them to
microtubules, actin filaments and to adhesive structures in the
desmosomes.
Nuclear envelope surrounded by intermediate filaments
Intermediate filaments in cytoplasmic are form ropelike
structures.
Intermediate filaments at the surface of the inner nuclear
membrane are organized in a 2D meshwork.
The intermediate filaments form nuclear lamina.
Microtubules globular tubulin
They grow form an organizing center.
Interphase cell
Dividing cell; during dividing there are 2 organizing center; spindle poles. 3
types of microtubules involved in ‘spindle formation’
o Aster microtubules
o Kinetochore microtubules
o Interpolar microtubules
Ciliated cell; organizing center; basal body.
Hollow tubes with structurally distinct ends
Hollow tubes; lumen in, outer consist of beta-tubulin (plus end) and alfa-
tubulin (minus end) subunit. These subunits are hold together by
noncovalent interactions.
This causes polarity; directional arrow embodies in the structure
In a growing tube, tubulins are added more rapidly to the plus end than to
the minus end.
Minus end is to the center and the plus end is away from the center
Centrosome is the major microtubule organizing center in animal cells
Centrosome, organize microtubules outward through the cytoplasm.
The centrosome consists of a pair of centrioles, surrounded by matrix of
proteins.
Growing microtubules display dynamic instability
Growing of the microtubules;
Addition of alfa beta-tubulin to the plus end.
The microtubule suddenly undergoes a transition that causes
it to shrink rapidly, and then suddenly start growing again.
Cytoskeleton; network of protein filaments in the cytoplasm.
Support large volume of cytoplasm
Responsible for large-scale movements
Controls the location of organelles and provides the machinery for transport
between them
Segregation of chromosomes into 2 daughter cells at cell division
Cytoskeleton consist of;
Intermediate filaments; structural elements crossing the cell. Go from one side
of the cell to other side. They determine the shape of the cell. Desmosomes
have on their side’s intermediate filaments. provide cell with mechanical
strength
Microtubules; Have a center from which they originate and stretch out through
the cell enable cells to move (sperm)
Actin filaments; organized around the cell membrane. muscle
contract/movment
Intermediate
filaments fibrous protein subunits
They bind via desmosomes.
They are also found in the nucleus of eukaryotic cell
nuclear lamina, underlies nuclear envelope
They prevent rupture. When a cell stretches and there is
intermediate filament in it cells stretch but don’t break they
remain intact and together
Strong and ropelike
They are ropelike strands. Self-assembly proteins
1. They have a N-terminus and C-terminus; alfa-
helix region of monomer
2. Coiled-coil dimer
3. Staggered tetramer of two coiled-coil dimers
4. Two tetramers packed together end-to-end
8 tetramers
5. Eight tetramers twisted into a ropelike
filament
All the interactions between the filaments depend on noncovalent bonding
Strengthen cell against mechanical stress
They have different names in cytoplasmic and in nuclear
Cytoplasmic
o Keratins; in epithelia
, o Vimentin and vimentin-related; in connective tissue, muscle cells and
neuroglial cells
o Neurofilaments; in nerve cells
Nuclear
o Nuclear lamina; in all animal cells
Accesory (aanvullend) protein (plectin) cross link them to
microtubules, actin filaments and to adhesive structures in the
desmosomes.
Nuclear envelope surrounded by intermediate filaments
Intermediate filaments in cytoplasmic are form ropelike
structures.
Intermediate filaments at the surface of the inner nuclear
membrane are organized in a 2D meshwork.
The intermediate filaments form nuclear lamina.
Microtubules globular tubulin
They grow form an organizing center.
Interphase cell
Dividing cell; during dividing there are 2 organizing center; spindle poles. 3
types of microtubules involved in ‘spindle formation’
o Aster microtubules
o Kinetochore microtubules
o Interpolar microtubules
Ciliated cell; organizing center; basal body.
Hollow tubes with structurally distinct ends
Hollow tubes; lumen in, outer consist of beta-tubulin (plus end) and alfa-
tubulin (minus end) subunit. These subunits are hold together by
noncovalent interactions.
This causes polarity; directional arrow embodies in the structure
In a growing tube, tubulins are added more rapidly to the plus end than to
the minus end.
Minus end is to the center and the plus end is away from the center
Centrosome is the major microtubule organizing center in animal cells
Centrosome, organize microtubules outward through the cytoplasm.
The centrosome consists of a pair of centrioles, surrounded by matrix of
proteins.
Growing microtubules display dynamic instability
Growing of the microtubules;
Addition of alfa beta-tubulin to the plus end.
The microtubule suddenly undergoes a transition that causes
it to shrink rapidly, and then suddenly start growing again.
