1.What are three main components of the cytoskeleton and what are the difference

Question

1.What are three main components of the cytoskeleton and what are the differences between them with respect to structure, function, and composition?   

2. Mammalian cells growing in culture spontaneously develop a strange phenotype with respect to mitochondrial location within the cell.  The fluorescence cytology below shows the relative locations of microtubules and mitochondria in the wild type and mutant cells. What protein is most likely defective and what is its normal function?   

3. Microtubules can be formed in vitro from tubulin that is bound to non?hydrolyzable GTP analogues. What properties would you expect these microtubules to possess?

4. What is “Dynamic Instability” with respect to microtubules?

5. What cellular effects would be seen with mutations in the genes encoding each of the following?   a. ??tubulin b. ??tubulin   c. kinesin   d. dynein

Explanation / Answer

There are three main components of the cytoskeleton: microtubules, microfilaments and intermediate filaments. The following differences are present among them:

Microtubules: these are polymers of tubulin. They have innder diameter of 12nm ehile the outer diameter is about 25 nm. These are polymers of dimer of tubulin. Total 13 dimers are present in their structure. The main functions of them are; preventing the cell against compression, facilitating cell motility and help in cell transport.

Microfilaments: these are made of actin polymers. They are about 7 nm in diameter and made from two strands of actin. They help in cell motility and also contribute as creating different cell shapes: microvilli, filopodiaand and lamellipodia.

Intermediate filaments: intermediate filaments are keratin polymers. Their diameter is about 10 nm. The intermediate filaments are highly dynamic in protein composition. There are many types of keratins which are made of 15 different proteins and designated as number from I to XV. For example type I and type II keratins are hard and some are soft. Some type III is made of vimentin and some are made of desmin. Type I and II keratins are used to develop hair, nails, and horns. Type III intermediate filaments are used in fibroblasts, white blood cells and smooth muscle cells.

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