Question

The principal protein of cilia and flagella is
A. Tubulin
B. Albumin
C. Globulin
D. Actin

Answer 1

The types of projections arising from cells of various organisms are known as cilia and flagella. The subunit which makes up these extensions are known as microtubules. These structures make up the cytoskeleton.

Complete answer: Microtubules are a polymer which is made up of proteins known as tubulin. It It is a major component of the cytoskeleton in various eukaryotic cells. The cilia and flagella are made up of $9 + 2$ arrangement of microtubules. It is a dimer made up of two types of tubulin subunits, the $\alpha$ and $\beta$ subunits. These structures create a wave-like movement upon the using up of ATP molecules. The major functions of these structures are in cell motility, also facilitating the movement of fluids within the cells. The basic structure of both of these are the same but varies in length.

Hence, the correct answer is option B.

a) Albumin: It is a globular protein constituting a major class of proteins present in the blood or serum. The major function of this protein is in the maintenance of osmotic pressure of blood. A wide variety of medicinal molecules also binds to this protein.
b) Globulin: These are water-insoluble proteins having a wide variety of functions. These make up the antibodies in the organisms which constitute the immune system and fight against infections.
c) Actin: This type of protein has many functions, one of the major functions is constituting the muscle fibres with another protein called myosin and helps in muscular contractility. It also helps in cellular division, organelle movement and even cell motility.

Note: Other functions of microtubules include the maintenance of the cell structure. It constitutes mitotic spindles and gets involved in cellular division. It also involves the expression of genes. During cell division, the microtubules act as a connecting point to the centromere of the chromosomes, this happens mostly in meiosis.