Cytoskeleton

• Thinnest of the 3 filaments (5-9nm)
• Made of actin proteins
• Concentrated beneath the cell cortex
• Very prominent in muscle cells
• Important for muscle contraction
• Motor proteins: myosin

• 10nm
• Made of intermediate filament proteins, which are not globular
• Important for mechanical support
• Do not have associated motor proteins

• Thickest of the filaments at 25nm diameter
• Made of tubulin proteins
• Tubulin forms a hollow ring structure called a heterodimer
• Very important for moving chromosomes during mitosis
• Responsible for moving organelles around the cell (Golgi, ER)
• All microtubules are anchored to the microtubule organising centre (MOC), which allows the microtubules to grow and shrink
• Associated motor proteins are kinesin and dyenin 

• Kinesins motor almost like 'walking along'

1. The leading head (1) is bound to tubulin and the trailing head (2) is bound to ADP

2. Head 1 binds to ATP which throws head 2 forwards

3. Head 2 binds to tubulin and releases ADP 

4. Head 1 hydrolyses ATP