Lecture 21: Cells and a skeleton?
Cytoskeleton: important structures
Size
a) Microtubules 25 nm
b) Microfilaments 7 nm
c) Intermediate Filaments 8-12 nm
**these are all interconnected and may have
overlapping functions; dynamic structures
The Microtubules
•Hollow tube
•Formed from protein tubulin
•Has polarity (NOT charged)
•13 protofilaments form tube
protofilament Table 6.1
Functions of Microtubules
1) Maintenance of cell shape (especially animal cells)
Cells….Not Round?
Fig 48.4
www.kurzweilai.net/meme/frame.html?main=/articles/art0183.html?m%3D3
Functions of Microtubules
1) Maintenance of cell shape (especially animal cells)
2) Movement of organelles
Kinesin
• Move along microtubule “tracks” towards the + end
• Links directly to vesicle or organelle
• Requires energy (ATP)
Link
Fig 6.21
Dynein
• moves toward the minus end
• dynactin attaches vesicle to microtubule and dynein moves it
From: Molecular Biology of the Cell (2002)
Functions of Microtubules
1) Maintenance of cell shape (especially animal cells)
2) Movement of organelles
3) Chromosome movements (form mitotic spindles)
4) Components of cilia and flagella (cell movements)
More on Microtubules
• Cilia beating
Fig 6.24
More on Microtubules
• Flagella movement
Fig 6.23