Cytoskeleton Continued
Terms
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- What is the major subunit of microtubules?
- Actin
- What are the 3 types of cytoskeleton proteins?
-
Intermediate Filaments - rope-like fibers, assembly regulated by phosphorylation, protect from mechanical stress
Microtubules - hollow cylinders composed of tubulin, originate from MTOC, assembly by GTP hydrolysis, aid in vesicle and organelle movement, axonal transport, cell division, comprise cilia and flagella
Microfilaments - composed of actin, important for cell locomotion and muscle contraction - Where do the forces, that move the cell forward, generated?
- cortex
- What pushes forward the leading edge of a lamellipodium?
-
-assembly of an actin network
-actin polymerization at this leading edge of the cell pushes the plasma membrane forward and forms new regions of actin cortex - What is the surface that the cell crawls on?
- substratum
- What is the leading edge of the cell called? Describe it.
- lamellipodium: sheet-like, contains dense meshwork of actin filaments, oriented so that most of the filaments have their plus ends close to the plasma membrane
- What do the focal contacts contain?
-
integrins
(transmembrane proteins in their plasma membrane) adhere to molecules in the extracellular matrix or on te surface of another cell over which the moving cell is crawling - What draws the rear end of the cell forward?
- contraction
- What is the filopodia?
- extend from the cell, thin/stiff protrusions both at leading edge and elsewhere on the surface
- What is an ARP?
- Actin related protein that promotes the formation of branched actin filaments. these proteins form a complex that binds to the existing actin filaments where they nucleate the growth of a new filament which grows out at an angle to form a side branch (formn of 2d actin web). With additional help of actin-binding protens (capping proteins etc) help to push the lamellipodia forward. (mediates nucleation of new actin filaments)
- What protects the actin filament plus ends (preventing further assembly or disassembly from old plus ends at the front of the array)?
- Capping proteins
- Depolymerizing protein?
- hydrolysis of ATP bound to polymerized actin subunits promotes depolymerization at the rear end of the actin complex
- What are cell locomotion and shape changes important for?
- wound healing
- What regulates the arrangement of actin filaments?
- GTP binding proteins (Rho protein binding family) which affect the arrangement of actin filaments in different ways (Cdc42-triggers actin polymerization and bundling to form the filopodia , Rac GTP-binding protein-promotes formation sheetlike lamellapodia formation)
- Cdc42
- triggers actin polymerization and bundling to form filopodia
- Rac
- promotes sheetlike lamellapodia formation
- What is the motor protein for actin?
- Myosin