Question

Which of the following statements about microtubules is correct?

Q 17-4 Homework • Unanswered • Due in a day Which of the following statements about microtubules is correct? We know that depolymerization of microtubules is important for the function of a mitotic spindle apparatus because the drug colchicine blocks cell division. O B Microtubule structure consists of a 9+2 arrangement of protofilaments. 0 C Protection of the GTP cap by stabilizing proteins is required for the formation of stable microtubule structures. O D Polymerization of tubulin into microtubules requires the hydrolysis of ATP to ADP + Pi. O E Because microtubules are subject to dynamic instability, they are used only for transient structures in a cell.

Answer 1

Microtubules are proteinaceous structures to support the extensive system of membranes and are found in cilia, flagella, centrioles and basal bodies, mitotic apparatus, etc. The alkaloid colchicine inhibits the formation of mitotic spindle by inhibiting polymerization of microtubules and holds the cells at metaphase. This drug binds with tubulin and inhibits polymerization and thus microtubules depolymerize for the proper functioning of mitotic spindle on account of cell division block.

The cilia and flagella have a microtubular composition. Miicrotubule structure has (9+2) organisation of protofilaments in cilia and flagella in eukaryotes.

Hydrolysis of ATP( GTP) to ADP and Pi weakens the binding affinity of tubulin for adjacent molecules thereby favoring depolymerization of microtubules.

The microtubule associated proteins (MAPs) stabilize the microtubule by protecting the GTP cap, as a result of which microtubules retain the GTP cap and continue to grow by adding GTP bound tubulin molecules.

Dynamic instability of microtubules results from the hydrolysis of GTP in which individual microtubules alternate between cycles of growth and shrinkage. So due to its dynamic instability nature microtubules finds it use only in transient structures in a cell like spindle, astral rays, cilia and flagella, centrioles, etc.

So the correct option is A, C and E.