1. AH Biology: Unit 1 Protein control of cell division: The Cytoskeleton

2. Cytoskeleton LOs
The cytoskeleton gives mechanical support and shape to cells. It consists of different types of proteins extending throughout the cytoplasm. Microtubules are composed of hollow, straight rods made of globular proteins called tubulins govern the location and movement of membrane-bound organelles and other cell components.
Microtubules are found in all eukaryotic cells and radiate from the centromere (the microtubules organising centre). Microtubules form the spindle fibres, which are active during cell division.

3. A cell must arrange itself in three-dimensional space and interact physically with its surroundings.
Watch animation before starting the topic. Students try to identify cellular processes that are familiar to them and justify their thoughts. Watch again after completing the cytoskeleton topic with emphasis on the role of the cytoskeleton. See separate document for description of events.
No cytoskeletal elements visible in diagram!
How many cell structures and processes can you identify in the Inner Life of the Cell animation?

4. The cytoskeleton
An intricate and interconnected system of protein filaments that extends from the nucleus to the plasma membrane.
Found exclusively in eukaryotic cells.

5. 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.
Link to white blood cell chasing bacterium and a moving amoeba.

6. 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.

7. Components of the cytoskeleton found in all eukaryotic cells
Actin filaments (also known as microfilaments)
Intermediate filaments
Microtubules

8. Actin filaments (microfilaments)
Two-stranded helical chains of actin monomers.
Arranged as linear bundles or networks, eg cell cortex beneath plasma membrane.
25 nm

9.
Stained mice fibroblasts

10. Actin filaments (microfilaments)
Networks of actin filaments reinforce the cell surface.
Involved in restructuring the cell surface during cytokinesis.
Involved in muscle contraction.
Acting in grey, myosin in red.

11. 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.

12. Intermediate filaments have been labelled with antibodies.

13. Lamins are intermediate filaments that form a meshwork called the nuclear lamina to reinforce the nuclear envelope.

14. Microtubules Largest element of the cytoskeleton.
Hollow cylinders composed of monomers of tubulin proteins.
25 nm

15. www.ncbi.nlm.nih.gov/.../ NBK26862/bin/ch16f6.gif.
Growth (by polymerisation) is fastest at the plus end.

16. Microtubules are dynamic structures
Animation of microtubule polymerisation.

17. Microtubules radiate from a specific cellular location.
The microtubule-organising centre (MTOC).

18. Animal cells have a single well-defined MTOC: the centrosome.
Nucleated microtubules
A pair of centrioles help to organise and duplicate the centrosome
Centrosome is found close to the nucleus.
In plant cells microtubules radiate from a number of sites around the nuclear envelope.
In fungi microtubules radiate from a MTOC embedded in nuclear envelope: the spindle pole body.
TuRC = tubulin ring complex: template for nucleating microtubules.
Clips of stained microtubules showing dynamic behaviour and unstable microtubules.

19. Microtubules
Microtubules form a network of intracellular ‘railway tracks’ along which transport of organelles occurs, eg vesicles and mitochondria.
Kinesin movement depends on conformational changes.
Video clip of kinesin motor protein moving along microtubule.
Movement of organelles along microtubles.

20. Rearrangement of cytoskeleton during cell division
Multinucleate cell in Drosophila early embryo.

21. Microtubules form spindle fibres
Kinetochores are stained red.

22. Spindle fibres attach to replicated chromosomes

23. Spindle fibres form the mitotic spindle
Kinetochore microtubules

24. Spindle fibre shortening separates the replicated chromosomes
Clips of chromosome separation: cultured lung cell and lily.

25. Role of spindle fibres in mitosis: animation.

26. Can you identify the elements of the cytoskeleton and their function in the Inner Life of the Cell animation?

27. Cytoskeleton LOs
The __________ gives mechanical support and shape to cells. It consists of different types of proteins extending throughout the ________. Microtubules are composed of _____, straight rods made of ______ proteins called ________ govern the location and movement of membrane-bound organelles and other cell components.
Microtubules are found in all ________ cells and radiate from the _________ (the microtubules organising centre). Microtubules form the ______ _______, which are active during cell division.

28. Cytoskeleton LOs
The cytoskeleton gives mechanical support and shape to cells. It consists of different types of proteins extending throughout the cytoplasm. Microtubules are composed of hollow, straight rods made of globular proteins called tubulins govern the location and movement of membrane-bound organelles and other cell components.
Microtubules are found in all eukaryotic cells and radiate from the centromere (the microtubules organising centre). Microtubules form the spindle fibres, which are active during cell division.