The scaffold of the cell Flashcards
What are the three components of the cytoskeleton?
Actin microfilaments
Tubulin microtubules
Intermediate filaments
What are cytoskeleton filaments made of?
Smaller subunits
What is the role of microtubules?
Maintenance of cell shape
Swimming and surface movement of fluids (cilia)
Mitotic spindle in mitosis
Protein transport
What are microtubules attached to?
A centrosome or centriole
A basal body
Describe tubulin
A dimer of 100kDa
Alpha and beta subunits
Can bind two GTP molecules
Describe the structure of a microtubule
Tubulin heterodimer forms a protofilament
Many protofilaments form a microtubule with a lumen in the middle
Describe the process of in vitro microtubule growth
Tubulin monomers form dimers Dimers polymerise into oligomers Oligomers grow into linear protofilaments Microtubules form Elongate by reversibly adding dimers Preferentially at the +ve end
Where do microtubules originate from in vivo?
Microtubule organising centre
Describe tubulin
A dimer of 100kDa
Alpha and beta subunits
Can bind two GTP molecules
Describe the structure of a microtubule
Tubulin heterodimer forms a protofilament
Many protofilaments form a microtubule with a lumen in the middle
Describe the process of in vitro microtubule growth
Tubulin monomers form dimers Dimers polymerise into oligomers Oligomers grow into linear protofilaments Microtubules form Elongate by reversibly adding dimers Preferentially at the +ve end
How are microtubules affected by drugs?
Drugs either inhibit polymerisation or promote it
When are microtubule drugs used?
Anti cancer agents
Disrupts mitosis and cell division
What are microtubule associated proteins?
A family of proteins that bind to and stabilise microtubules
What is the function of MAPs?
The binding of MAPs makes polymerisation quicker
Stabilises the microtubules
Binds the microtubule to other microtubules or actin or vesicles
Which is the thickest cytoskeletal filament?
Microtubules at 25nm
Name some structures formed by actin filaments
Microvilli
Filopodia
Contractile ring
How large is actin?
An actin monomer is 42kDa in size
What is the role of actin filaments in cells?
Maintenance of cell shape
Cell movement and chemotaxis
Interaction with the environment
Movement of vesicles, proteins and organelles
Name some structures formed by actin filaments
Microvilli
Filopodia
Contractile ring
What are the three subtypes of actin?
Alpha
Beta
Gamma
What binds to actin?
1 molecule of ATP or ADP
What is the monomer of actin?
G-actin
What is the polymer of actin?
F-actin
How many iso forms of actin are there?
4 in muscle
2 in cytoskeleton
How large is an F-actin filament?
5-9nm diameter
What is the structure of an F-actin filament?
2 stranded twisted beads
What are actin binding proteins?
A family of proteins that regulate actin filaments
Describe the monomer of an intermediate filament
Chain with heads at each end
What is the dimer of intermediate filaments?
Coiled-coil
Two monomers twisted round each other
What is the tetramer of an intermediate filament?
Two coiled coils are staggered, side by side
How does a intermediate filament form?
8 staggered tetramers wide
Twisted into a rope like filament
Give an example of an intermediate filament within the cell
Keratin
Which cytoskeletal filaments are contractile?
Microfilaments
Microtubules
What is the diameter of an intermediate filament?
10nm
Which cytoskeletal filaments are deformable?
Microtubules
Intermediate filaments
Which cytoskeletal filaments can withstand force?
Microfilaments
Intermediate filaments
