Lec 2.5 Cytoskeleton structure I Flashcards
What are the 3 families of proteins that deal with the cytoskeleton?
Actin filaments, Microtubules, Intermediate filaments.
What are the 8 functions of the cytoskeleton?
- Orginization of the cell. 2. Moves the cell. 3. Re-arranges the cellular compartment. 4.Supports the plasma membrane. 5. Provides mechanical strength 6. Pulls chromosomes apart. 7. splits dividing cells. 8. Guides intracellular traffic of organelles.
What helps RBC be that biconcave shape?
Cytoskeleton
What if the RBC cytoskeleton is defective?
Anemia. HS.
What is HS (hereditary spherocytosis)?
Fragile RBCs.
The cytoskeletal filaments consist of what?
Protofilaments
What are protofilaments?
Long linear strings of protein subunits joined end to end
What do Actin filaments determine?
the shape of cells surface.
What are Actin filaments necessary for?
Cell locomation, secretion and endocytosis
What do Microtubules determine?
Positions of membrane enclosed organelles
What do Microtubules do?
Direct intracellular transport. Separate chromosomes.
What do microtubules make up?
Cilia, flagella and centrioles and mitotic spindle.
What are microtubules made up of?
Tubulin subunits
What do intermediate filaments do?
Provide mechanical strength, resist mechanical strength. Formation of hair and fingernails
Intermediate filaments are like what?
Rope-like
How do intestinal cells get more nutrients?
With microvilli(actin). More surface area.
What side of the cell absorbs nutrients?
Apical surface
What side of the cell transfers nutrient to blood stream?
Basolateral surface
Actin monomer contains a binding site for what?
ATP or ADP
Actin filaments consist of what?
two protfilaments that twist around each other.
With actin filaments, what are the 2 distinct ends?
Plus and minus end
What is the plus end?
Fast growing or fast shrinking end
What is the minus end?
Slow growing or slow shrinking end
With ATP-actin subunits do what?
Grow
With ADP-Actin subunits do what?
shrink
How do tubulin subunits associate?
Self associate, end to end and side to side protein interactions
What does it mean that tubulin is a hetero dimer?
Means tubulin is made up of alpha tubulin and beta tubulin.
What is the binding site for both alpha and beta tubulin?
One GTP
How do beta and alpha tubulin bind?
Beta tubulin binds to bottom of alpha.
Do microtubules also have a plus and minus end?
Yes
What is nucleation?
initial aggregate of subunits first assembling.
What is nucleoside hydrolysis?
Pertaining to actin and tubulin. Each monomer carries a tight bound ATP or GTP, and that is hydrolyzed to ADP or GDP soon after the monomer assembles into the polymer.
What does the T form mean pertaining to nucleoside hydrolase?
ATP or GTP bound
What does the D form mean pertaining to nucleoside hydrolase?
ADP or GDP bound
Plus end remains in what formation?
T form
Minus end remains in what formation?
D form
What does nucleoside hydrolase leads to ?
treadmilling
What is treadmilling?
Plus end grows while the minus end shrinks
Addition of GTP to tubulin results to what?
Straight protfilaments
Addition of GDP to tubulin results to what?
Loose protofilaments
What type of stability usually predominated in microtubules?
Dynamic Instability
Unlike actin or microtubules, intermediate filaments dont have what?
No nucleotide binding site
What is an example of intermediate filaments?
Keratins (make up hair and nails).
Define and differentiate nucleation, catastrophe and rescue.
initial aggregate of subunits first assembling. Catastrophe is change from growth to rapid shrinkage. Rescue is change from rapid shrinkage to growth.
Describe treadmilling in actin filaments
Plus end grows while the minus end shrinks
