Spindle fibres are formed of microtubules, which play an important role in movement of chromosomes and centrioles during cell division. Biochemically a profilament of microtubule is made of a protein called tubulin. Tubulin is an acidic protein, which occurs in two different forms called α -tubulin and β -tubulin. Cytoplasmic microtubules are highly dynamic structures constantly forming and dis-appearing depending on cell activities.
Myosin is fibrous functional protein of muscle. Myoglobin protein of muscle cells act as a reservoir of oxygen. Albumin is the smallest and most numerous proteins in the blood which are involved in cargo of toxic materials.