MCB Lecture 34 Cytoskeleton I Flashcards
What are the three classes of filament?
Microfilaments / actin
Microtubules
Intermediate filaments
What are some general functions of the cytoskeleton?
Cell shape
Cell locomotion
Resistance to compressive forces
Movement of organelles within a cell
What is an example of intermediate filaments?
Keratin, rope like, very strong
What are the general features of intermediate filaments?
Very strong and rope like
Describe intermediate filament formation
Alpha helix synthesised
Two alpha helices form a coiled coil: dimer
Two dimers interact
Protofilament: four dimers interacting
Many protofilaments line up to form the rope like filament
Describe the polarity of intermediate protofilaments
They are non polar, since the protofilaments line up anti parallel
What are some general features of actin filaments?
They are flexible
Describe the formation of actin filaments
G-actin monomers bind head to tail to form a string
Two strings intertwine to form a protofilament
Many protofilaments are connected by cross-linking proteins
Differentiate between F and G-actin
G-actin are the individual subunits
F-actin is the filament formed
Describe the polarisation of actin filaments
Since the monomers line up head to tail, the filament is polarised, and has a plus and a minus end
What is the function of cross linking proteins inaction filaments?
Forms the assemblies of actin filaments
Describe the function of contractile belts, and which type of cytoskeleton filaments is involved
The contractile belts carry out epithelial folding
Actin and Adherens junctions are involved
Describe the function of migratory processes, and which cytoskeletal filaments are involved
Migratory processes extend out so that the cell can move
Actin is involved
What is the function of the cell cortex?
What are some of the proteins involved?
The cell cortex forms the broad protrusions during cell locomotion (lamellipodium)
Filamin
Spectrin
What is Filamin?
This is a protein that binds to actin filaments in the cell cortex.
It allows lamellipodium formation
What is Spectrin?
This is a protein that binds to actin filaments in RBC, regulating mesh work
What is a lamellipodium? Compare with a Filopodium
This is the broad protrusion, actin is more disordered
Filopodia are smaller protrusions with ordered bundles of actin