Question

Microtubules are made up of

• A. Actin
• B. Tubulin
• C. Fibrin
• D. Nexin

Answer 1

The correct option is B Tubulin

Cilia and Flagella are made up of microtubules. The axis of a cilium or flagellum consists of microtubules arranged in a nine fold radial symmetry and is called the axoneme. It consists of 11 longitudinal fibrils (2 central and 9 peripheral). Each microtubule is a hollow cylinder composed of 13 longitudinal protofilaments. The protofilaments appears to be made up of a linear series of globular protein tubulin units like a string of beads. Under normal physiological conditions tubulin is a dimer composed of two similar but not identical polypeptides. The two subunits of a tubulin dimer are called $\alpha$ and $\beta$ tubulin with molecular weights of 55,000 and 57,000.