Transcript Unit 1 PPT 10 (2fi Cytoskeleton)

AH Biology: Unit 1
The Cytoskeleton
A cell must arrange itself in three-dimensional
space and interact physically with its
surroundings.
How many cell structures and processes can you identify in
the Inner Life of the Cell animation?
The cytoskeleton
• An intricate and interconnected system of
protein filaments that extends from the
nucleus to the plasma membrane.
• Found exclusively in eukaryotic cells.
Roles of the cytoskeleton
- Provides a framework of mechanical support
to a cell, which allows it to maintain its shape.
- Allows the movement of cell organelles.
- Allows the movement of whole cells, eg white
blood cells and amoebae.
Roles of the cytoskeleton in cell
division
- Responsible for the movement of chromosomes
during the processes of meiosis and mitosis.
- Responsible for the division of the cytoplasm
(cytokinesis) in animal cells.
Components of the cytoskeleton found
in all eukaryotic cells
• Actin filaments (also known as
microfilaments)
• Intermediate filaments
• Microtubules
Actin filaments (microfilaments)
• Two-stranded helical chains of actin monomers.
25 nm
• Arranged as linear bundles or networks, eg cell
cortex beneath plasma membrane.
Actin filaments (microfilaments)
- Networks of actin filaments reinforce the cell
surface.
- Involved in restructuring the cell surface during
cytokinesis.
- Involved in muscle contraction.
Intermediate filaments
• Rope-like fibres that are composed of fibrous proteins
from a large family.
• Involved in the maintenance of the shape of whole
cells or parts of cells, including the nuclear envelope.
Microtubules
- Largest element of the cytoskeleton.
- Hollow cylinders composed of monomers of tubulin
proteins.
25 nm
Microtubules are dynamic structures
Animation of microtubule polymerisation.
Microtubules radiate from a specific cellular
location.
The microtubule-organising centre (MTOC).
Animal cells have a single well-defined MTOC:
the centrosome.
Nucleated
microtubules
A pair of centrioles
help to organise
and duplicate the
centrosome
Clips of stained microtubules showing dynamic behaviour and unstable microtubules.
Microtubules
Microtubules form a network of intracellular ‘railway tracks’
along which transport of organelles occurs, eg vesicles and
mitochondria.
Video clip of kinesin motor protein moving along
microtubule.
Movement of organelles along microtubles.
Rearrangement of cytoskeleton during cell
division
Microtubules form spindle fibres
Spindle fibres attach to replicated
chromosomes
Spindle fibres form the mitotic spindle
Kinetochore microtubules
Spindle fibre shortening separates the
replicated chromosomes
Clips of chromosome separation: cultured lung cell and lily.
Role of spindle fibres in mitosis: animation.
Can you identify the elements of the
cytoskeleton and their function in the Inner Life
of the Cell animation?