The Cytoskeleton Flashcards
What are the major functions of the cytoskeleton?
- Maintains cell shape
- Responds to environment
- Aids cellular movement
- Intracellular / organelle movement
Explain what the cytoskeleton is
A microscopic network of protein filaments and tubules in the cytoplasm of living cells, giving them shape and coherence
What is G-actin?
Globular actin - a protein monomer
Which is the thinnest class of cytoskeleton filaments?
F actin (7nm)
Which 3 polymers is the cytoskeleton composed of?
Actin Filaments
Intermediate Filaments
Micro tubules
Outline how the filament monomers are able to polymerise and depolymerise
- Cell receives signal via receptors
- Existing filaments depolarise to form free monomers in the cell
- Monomers diffuse rapidly
- Reassemble at new site
What are accessory proteins?
Proteins ensuring correct protein folding in the right location
Describe the structure of intermediate filaments
Rope-like structure Many long strands twisted together Composed of different sub units Forms a network throughout cytoplasm Joins at desosomes
How is F-actin formed?
G-actin monomers join together to form filaments
Describe the structure of microtubules
Hollow tubules made of tubulin Rigid Long straight chains Polarised Dynamic structure
Why is F actin polar?
Shows structural polarity due to fast growing +ve end
What are ABPs?
Actin Binding Proteins
What type of actin is found in muscle cells?
ɒ actin
Explain the advantage of intermediate filaments being so tough?
Withstands mechanical stress when cell is stretched
strengthens nuclear envelope
What do Synamin and plectin collectively do?
( Bind desmind and vimentin together )
Links Intermediate fiaments to other compounds
Why is the centrosome the optimal MTOC?
Contains ɣ tubulin ring that initiates micro tubule growth
What is the function of Plakins?
Maintains contact between desosomes of epithelial cells
How many different isoforms of G-actin are there?
there are 3 different isoforms
What do accessory proteins regulate?
- Nucleation (site & rate of protein filament formation)
- De/polymerisation
- Protein function
Which of the cytoskeleton filaments is the toughest?
Intermediate filaments are the toughest - resistant to detergent & high salts
Where is the MTOC of most cells?
Centrosomes in percinucleur region
Which cells are IFBPs found in?
All nucleated eukaryotic cells
What is the difference between the 3 different isoforms of G-actin?
They each have different isoelectric points
Which functions are carried out by the cytoskeleton microtubules ?
Organelle positioning
Intracellular transport
Describe the structure of actin filaments
Helical polymers made of actin
Flexible chain of globular actin (G-actin)
Organised into 2D networks and 3D gels
Where are majority of ABPs found?
Many ABPs in F actin
Explain how the cytoskeleton is dynamic
The filament monomers continuously polymerise and depolymerise