Question

Select the correct option:
Microtubules are absent in
A. Mitochondria
B. Flagella
C. Spindle fibres
D. Centriole

Answer 1

Hint: Microtubules refers to the polymers of tubulin. It is the part of the cytoskeleton and provides structure and shape to eukaryotic cells. They are mainly responsible for different movements in the eukaryotic cells.

Complete Answer:
Microtubules are the components of the cytoskeleton. They play a vital role in mitosis, cell motility, intracellular transport, and also maintenance of cell shape.

Let us analyze each option to find out the correct answer.
Option A: Mitochondria are double membrane-covered, semi-autonomous eukaryotic cell organelles whose function is cellular respiration. Mitochondria are also visible under a light microscope but a detailed study is not possible. Mitochondria were named by Carl Benda in 1898 from his study of cell internal structure and the first recorded information of mitochondria in plant cells. They play a vital role in mitosis, cell motility, intracellular transport, and also maintenance of cell shape. Therefore this is the correct option.

Option B: Flagella is a hairlike structure. It is usually found in bacteria, archaea, and eukaryotes, though they are most commonly found in bacteria. It acts primarily as an organelle of locomotion in the cells of many living organisms. They are typically used to propel a cell through the liquid. The microtubules are basic structures of spindle apparatus, centrioles, basal bodies, cilia, and flagella. The shaft of cilia and flagella consists of an external sheath, semifluid matrix, and an axoneme. Axoneme has a 9+2 fibrillar arrangement. Therefore, this is an incorrect option.

Option C: Spindle fibres consist of microtubules that are polymeric chains made from the protein tubulin. Therefore, this is an incorrect option.

Option D: Each centriole has a cartwheel constitution. There is a whorl of nine peripheral triplet fibers of tubulin tilted at an angle of 40 degrees. In general, microtubules are basic structures of spindle apparatus, centrioles, basal bodies, cilia, and flagella. Therefore, this is an incorrect option.

Thus, the correct option is A) Mitochondria.

Note: The various functions of microtubules are,
- They have an important role in cell division as they help in formation of mitotic spindles.
- They give structure to both cilia and flagella and therefore help the cell to move.
- They also help in movement of cellular organelles.