Cytoskeleton Flashcards
How long in diameter is each component of the cytoskeleton?
MT-20nm
MF- 7nm
IF - 10nm
What are the filaments of individual actin proteins made up of?
G-actin
How many actin subunits are there for a complete turn of the helix?
13
What is the shape of an actin filament?
Polarised double helix
How many nm is the length of a complete turn of the actin filament?
37nm
What does the asymmetric shape of the actin monomer lead to?
The polarity of the filament
Explain how the growth of the actin filament occurs?
Monomers are added to the filament with the use of ATP. Monomers are added more rapidly to the positive end. The ATP is hydrolysed in ADP.
What are the major functions of actin? (3)
- Mechanical support
- Cell shape and maintenance
- Cell motility
What can we add to G-actin monomers to stop it polymerising?
proteins
Where are IF most dense?
Around the nucleus
What is the main role of IF?
Mainly mechanical structure, used to anchor cells are some cell junctions. it supports nuclear structure and protects chromatin.
What are specialised intermediate filaments called and what do they do?
Lamins and they support nuclear structure and protect chromatin.
Explain the 4 step formation of the intermediate filament polymer?
- Intermediate filament polymer (monomer) held end to end
- This forms a helical dimer
- Two dimers combine to form a tetramer
- Tetramers link in a staggered formation and end-to-end to form the filament
Explain the structure of a microtubule and its subunits
The polymer is built from monomers of tubulin. There are 13 monomers in the cross-section. Tubulin monomers consist of an alpha tubular and one beta tubulin.
In the assembly of a microtubule, what energy releasing molecule is used?
GTP