The Cytoskeleton ● Network of Protein Filaments ● Used in: – Structural Support – Cell Movement – Movement of Vesicles within Cells ● Composed of three types of Cytoskeletal fibers – Actin Filaments – Microtubules – Intermediate Filaments
Feb 24, 2016
The Cytoskeleton
● Network of Protein Filaments● Used in:
– Structural Support– Cell Movement– Movement of Vesicles within Cells
● Composed of three types of Cytoskeletal fibers– Actin Filaments– Microtubules– Intermediate Filaments
The Cytoskeleton
● Actin Filaments– Smallest of the fibers, 7nm in diameter– Two protein chains, loosely twined– Each subunit is the globular protein actin– Polarity designates direction of growth– Turn on polymerization when appropriate– Responsible for cellular movements
The CytoskeletonActin Filaments
The Cytoskeleton
● Microtubules– Ring-shaped tubes, 25nm in diameter– Consist of 13 protofilaments, arranged side by side
around a central core– Facilitate cellular movement and move materials
within the cell– Form nucleation centers near center of cell
● + end of microtubule radiates away from nucleation center
● - end of microtubule radiates towards nucleation center
The Cytoskeleton
Microtubules
The Cytoskeleton
● Intermediate Filaments– Most durable of filaments– Tough, fibrous protein molecules twined together in
overlapping arrangement– Stable– Constitute mixed group of cytoskeletal fibers
● Vimentin (most common)● Keratin (epithelial cells)
The CytoskeletonIntermediate Filaments
The Cytoskeleton
● Microtubule Organizing Centers– Centrioles– Centrosome– Pericentriolar Material
The Cytoskeleton
● Centrioles– Barrel-shaped organelles– Found in cells of animals and protists– Occur in pairs– Located in right angles to each other outside the
nuclear membranes
The Cytoskeleton
● Centrosome– Region surrounding centrioles– Responsible for reorganization of microtubules that
occurs during cell division– Centrosomes of plants and fungi lack centrioles
The Cytoskeleton
The Cytoskeleton
● Pericentriolar Material– Contains ring-shaped structures composed of
tubulin– Nucleates the assembly of microtubules in animal
cells– Called microtubule-organizing centers
The Cytoskeleton
Pericentriolar Material
The Cytoskeleton
● Movement of Materials within Cells– Use of Actin Filaments in cells allows for movement– Cytoskeleton provides scaffold that holds certain
enzymes and other macromolecules in defined areas of cytoplasm
– By moving and anchoring particular enzymes near one another, responsible for organizing cell's activities
The Cytoskeleton
● Molecular Motors– A vesicle or organelle needs to be transported– A motor protein that provies the energy-driven
motion– A connector molecule that connects the vesicle to
the motor molecule– Microtubules on which the vesicle will ride like a
train on a rail