Cytoskeleton Flashcards
What is the cytoskeleton?
A dynamic, complex, intracellular network of tubules, filaments and fibres found in all eukaryotes
What is the cytoskeleton made up of?
- Microtubules
- Microfilaments/Actin filaments
- Intermediate filaments
- Associated proteins
(apart from in fungi)
What are the roles of microtubules?
- Determine position of membrane enclosed organelles
- Direct intracellular transport
- Form mitotic spindle that segregates chromosome
What are the roles of actin filaments?
- Determine shape of cell’s surface
- Necessary for whole cell locomotion
- Drive cytokinesis
What is the function of intermediate filaments?
Provide mechanical support
What are microtubules composed of?
Protofilaments: α and ß tubulin
What does MAP stand for? What do they do?
Microtubule associated protein
Either chop microtubules to promote disassembly or bind to side of microtubule to stabilise it
What types of microtubules are there?
- Cytoplasmic microtubules
- Special structures
- Stable and labile
Dynamic instability
When the [GTP] is too high. The GTP-capped end can be accidentally hydrolysed –> rapid shrinkage from previous ‘+’ end
What is an organising centre?
Pair of centrioles embedded in sea of proteins with nucleating sites/gamma tubule ring complexes
What is another name for the organising centre?
Centrosome
What does every microtubule grow out of?
The gamma-tubuling ring on a centrosome
What is found within the mass of centriole material?
Basal bodies (these help to form spindles)
Give examples of motor proteins
Dynein and kinesin
In monomeric form what does actin have bound to it?
ATP
When in filament form, what does actin have bound to it?
ADP
What is the function of the actin filament association protein profilin?
Promotes assembly
Recruits actin monomers for polymerisation at plus end
What is the function of the actin filament association protein thymosin?
Inhibits assembly
Binds actin monomers and prevents them from adding to plus end
What is the function of the actin filament association protein gelsolin?
Sits on end to stop growing
What is the function of the actin filament association protein fimbrin?
Responsible for close packing of actin filaments/bundling
Subunits of intermediate filaments
I and II - epithelial keratins
III - desmin in muscle
IV - neurofilaments
V - nuclear lamins
Which actin filament association protein sits on the end to stop growing?
Gelsolin
Which actin filament association protein inhibits assembly?
Thymosin
Which actin filament association protein promotes assembly?
Profilin
