Question

Describe structure, nature, role, assembly/formation and location of microtubules. Also name and describe the motor proteins that associate with microtubules, as well as the energy source for the movement.

Answer 1

Structure of microtubule= These are the largest cytoskeletal filaments in cells,with a diameter of 25 nanometers.They are made up of subunits called as tubulin.

Each tubulin subunit is made up of one alpha and one beta tubulin that are attached to each other,so is heterodimer.

In microtubule structure,tubulin monomers are linked both at their ends along their sides.

it has 2 distinct ends,called the plus and minus ends.

on the minus end ,alpha tubulin is exposed,& on plus end beta tubulin is exposed.

Microtubules preferntially assemble & disassemble at their plus ends.

Microtubule minus ends can be clustered together in a so called microtubule -organizing center,or centrosome.

Centrosome stays stable as the plus ends grow and shrink.

Role of microtubule-

has many important cellular functions.

1.Separation of sister chromatids during division -In this process,each daughter cell needs to get one complete set of chromosomes.The replication and separation of chromosomes is called mitosis.

During mitosis there are 2 centrosomes ,one at each end of the cell.and each with an array of microtubules stretching out from it.

The replicated chromosomes ,called chromatids,are lined up in pairs in the center of the cell.microtubules bind to the centers of each one and then,all at the same time,the microtubule begin to disassemble and shrink.

2.They move vesicles,granules,organelles like mitochondria and chromosomes via special attachment proteins

3.They serve as a cytoskeletal role.

Location of microtubule- microtubules are nucleated & organized by microtubule organizing centers ,such as centrosome found in the center of many animal cells or the basal bodies found in cilia and flagella,or the spindle pole bodies found in most fungi.

Motor proteins that associate with microtubules =

are dynein and kinesin

Dynein-

kinesin- these motor proteins that move along the microtubules.

They use the energy source such as ATP(Adenosine tri phosphate)