Question

The cilia and flagella both have
A. $9 + 2$arrangement of microtubules.
B. Protective structure of cells.
C. Only present in protozoa animals.
D. Only outgrowth structure of cytoplasm.

Answer 1

Hint:
Cilia and flagella are hair-like outgrowths from the cell. Their role is to either move the cell itself or move
the substances around the cell. Cilia are smaller in length as compared to the flagellum but they both have similar internal structure i.e., both of them are made up of microtubules.

Complete answer:
-Option (A) is correct. Both cilia and flagella have microtubules arranged in a $9 + 2$ array i.e., the 9 fused pairs of microtubules are located outside the cylinder and two unfused microtubules are located in the center of the cylinder. These are collectively called an axoneme.
-Option (B) is incorrect. Both cilia and flagella help in the locomotion of the cell or the substances over or
around the cell. Thus, these structures are not the protective structures of cells.
-Option (C) is incorrect. Cilia are only present in protozoa animals or eukaryotic animals while flagella is a
long slender outgrowth in both prokaryotic as well as eukaryotic animals.
-Option (D) is incorrect. Both cilia and flagella contain inner growth along with the outer growth of the
cytoplasm.
Hence, the correct option is (A).

Additional Information:
Cilia are of two types i.e., non-motile and motile cilia. The non-motile cilia are also known as primary
cilia that consist of $9 + 0$ arrangement of microtubules in which the axoneme is lacking the 2 unfused
microtubules in the center while the motile cilia have $9 + 2$ arrangement of microtubules.

Note:
The movement of cilia and flagella is due to the interactions of the set of microtubules present within
the structure. The protein dynein is attached to the microtubule that has a function of molecular motor.