Lecture 6 Flashcards
Cytoskeleton (23 cards)
List the three types of cytoskeleton components
- Microfilaments
- Intermediate filaments
- Microtubules
What function do the cytoskeleton components serve?
- Changes in the cell shape
- Provide structural framework for the cell
- phagocytosis
- mitotic spindle formation
- cytokinesis
- Interact with other cells and the extracellular matrix
- cell movement
Briefly describe actin polymerization
Actin monomers combine to form a trimer
There are drugs that affect polymerization and treadmilling, list them.
- Cytochalasins
- Phalloidin
What are actin binding molecules?
There are 7 actin-binding molecules that have specific functions that control treadmilling
List out each kind of actin binding molecule
- thymosin
- profilin
- gelsolin
- coflin
- Arp2/3
- phallodin
- latrunculins
Briefly describe the basic structure of intermediate filaments.
Intermediate filaments have a central alpha helical rod with head and tail domains
How are intermediate filaments assembled?
First, two IF monomers form a dimer, two dimers form a tetramer, and 8 tetramers associate laterally to form a unit length filament (ULF). Several ULFs line up longitudinally to form a mature Intermediate Filament.
Describe the structure of a microtubule
- Protofilaments of longitudinal rows of tubulin dimers
- 13 protofilaments arranged parallel around a hollow core
What is the function of Gelsolin?
Gelsolin destabilizes f-actin and caps the actin filaments which prevents the addition or loss of g-actin
What is the function of Cofilin?
Cofilin triggers the depolymerization of actin at the minus end
What is the function of Arp2/3?
Causes branching by initiating growth of F-actin
What is the function of phalloidin?
Binds to actin filaments to prevent depolymerization
What is the function of Latrunculins?
- Induces f-actin depolymerization
- binds to g-actin
What are the functions of Intermediate Filaments?
- Provide tensile strength
- Associates with other cytoskeletal elements to form a scaffolding that organizes the internal cell structure
During polymerization there is a growing end and an end that is being depolymerized. Which ends do ATP and ADP associate with?
- ATP associates with the growing end
- ADP associates with the depolymerizing end
The functional diversity of actin filaments is determined by what?
Actin-binding proteins NOT the actin itself
List 6 actin binding proteins:
- Spectrin- binds cortical cytoskeleton to plasma membrane
- Dystrophin -binds cortical cytoskeleton to plasma membrane
- Villin and Fimbrin - cross links in microvilli
- Calmodulin and Myosin I - cross links actin to plasma membrane in microvilli
- a-Actinin - cross links stress fibers, connects actin to plasma membrane complexes
- Filamin - cross links actin to form screen-like gels
How does treadmilling and dynamic instability relate to microtubule assembly and disassembly?
- In relation to treadmilling, the plus end of a microtubule grows more rapidly than the minus end in the presence of low calcium ion concentration.
- Microtubules go through alternating phases of slow growth and rapid depolymerization leading to dynamic instability.
What role do microtubules play in mitosis?
- anchors the mitotic center to the plasma membrane
- attach to centromeres on chromosomes
What is the mechanism of intraciliary transport?
kinesin and dynein mediate transport of materials along microtubules, sometimes aided by raft proteins.
What are the roles for microtubules and motor proteins in axonal transport?
The microtubule serves as the ‘monorail’ while the motor proteins move the organelles from the neurons cell body through the axoplasm.
Describe the two kinds of myosin.
- Myosin I has a single head and short tail that drives cargo movement such as secretory vesicles
- Myosin II has two heads that bind to actin that move towards the plus end
