The Cytoskeleton MCQ - Practice Questions & Answers

Concepts Covered - 1

The Cytoskeleton

The Cytoskeleton

Cytoskeleton refers to the network of protein fibres that help in maintaining the shape of the cell and help in the movement of the cell.
There are three types of protein fibres within cytoskeleton:

Microfilaments

These are the narrowest fibres made up of two intertwined strands of F-actin protofilaments. They are also called actin filaments.
F-actin protofilaments are made up of G-actin subunit.
F-actin is the filamentous actin while G-actin is the globular actin.
The individual strands of F-actin protofilaments are wound together with the help of tropomyosin.
Tropomyosin is a double-stranded alpha-helical coiled-coil protein.
It bears a protein complex, called troponin, which is interspersed along the length of the coil.

Functions of Microfilaments:

Microfilaments provide shape and rigidity to the cells. They can depolymerize (disassemble) and reform quickly, thus enabling a cell to change its shape and move.

Intermediate Filaments

They are called the intermediate filaments because their diameter (8 to 10 nm) is between those of microfilaments and microtubules.
These are structural in function.
They do not perform any role in the movement.
They maintain the shape of the cell by bearing the tension.
Their main function is to maintain the shape of the cell and provide tensile strength.
These are formed through the process of polymerization.

Microtubules

These are small hollow tubules.
Their walls are made up of polymerised dimers of a-tubulin and B-tubulin.
They have a diameter of 25 nm. They are the widest component of the cytoskeleton.
They help the cell resist compression, provide a track along which vesicles move through the cell and pull replicated chromosomes to opposite ends of a dividing cell.
Like microfilaments, microtubules can dissolve and reform quickly.