Cell Biology 3400

CBIO 3400 Exam 3 Study Guide

1. Describe in detail the three type of filaments that make up the cytoskeleton.

- Actin: unstable must have actin binding protein, stability depends on function, 10 nm diameter, filament has 2 strands, atp hydrolysis occurs during assembly, 42K dal. Protein, Globular actin polymerizes into filament actin, filament is helical structure, actin is polarized (+,- ends), G-actin bind to other G-actin in head to tail orientation to form F-actin, nucleation required for polymerization.

- MicroTubule (MT): long thick filament made of tubulin, makes up the (mitotic spindle, sperm flagella, cilia, intracellular transport network), dynamic, assembled from centrosome/basal body, more rigid then actin, non-dividing cells have interphase microtubule array while dividing have mitotic spindle, MTOC (minus ends of MT attach to centrosome, contribute to cell polarity, gamma tubulin associated with centrosome), Dynamic instability – rapid growth and shrinkage, - facilitated by tubulin monomer to hydrolyzed GTP

- Intermediate (IF): ropelike fibers of variable proteins, line nuclear lamina, provide structural integrity and mech. strength, 2 types plectin & keratin, keratin – found in epithelial cell, -comprise many tissue type(gut lining, skin, hair, feathers) ,- directly bind to desmosomes, plectin – accessory protein, - not necessary for formation of intermediate filament, - cross link IF for adding strength and stability, - link IF to other cytoskeleton networks and desmosomes.

2. Define the following terms: treadmilling, dynamic instability.

- Treadmilling – growth of filament at one end while other end shortens.

- Dynamic instability – MT undergo rapid growth and shrinkage. MT Polymerization (growth) – tubulin monomers add to free growing MT faster than GTP hydrolysis, - end side of growing end had GTP cap. MT Depolymerization (shrinkage) – tubulin hydrolysis GTP before next one binds, monomers bound to GDP rapidly...