TUBULIN

Q. Which of the following make up the cellular structures involved in axonal transport of vesicles?
(A) Desmin
(B) Keratin
(C) Titin
(D) Tubulin
 (E) Vimentin


Ans: D. Tubulin.


Exp. 

Microtubules are involved in the transport of vesicles down the axons of neurons. Microtubules are made of polymerized tubulin. The microtubule is made up of two subunits, that polymerize to form a hollow tubule. Two attachment proteins, dynein and kinesin, attach to membranous organelles and move along the tubules toward and away from the cell center.

Option  A is incorrect. Intermediate filaments of muscle cells are made up primarily of desmin.

Option  B is incorrect. Intermediate filaments are cytoskeletal elements that are prominent in cells that withstand stress. Intermediate filaments of epithelial cells are composed primarily of keratin.

 Option  C is incorrect. Titin, also known as connectin, is a protein that is important in the contraction of striated muscle tissues. In the sarcomere, titin connects the M line to the Z line.

Option E is incorrect. Vimentin is polymerized to form intermediate filaments that are found in cells of mesodermal origin, such as fibroblasts