Question

Which cell organelle is absent in the neurons?
(a) Mitochondria
(b) Ribosomes
(c) Centriole
(d) Nucleus

Answer 1

Hint: Neurons are cells which do not undergo cell division. They are the functional unit of the central nervous system and transmit signals in the body in the form of electrical messages.

Complete Answer:
Neurons consist of 3 parts - dendrites, the axon and the cell body. Dendrites are fibre-like projections responsible for receiving signals from neighbouring neurons. The axon is responsible for conducting action potentials across the cell body. The cell body of the neuron contains the nucleus and other cell organelles.
Mitochondria are responsible for the production of energy and hence are vital in any cell. The conduction and transmission of electrical signals requires energy and hence, this cannot be the right answer.
Ribosomes are the organelles responsible for the production of proteins through a process called Translation. They are often present in abundance, scattered across the cytoplasm. Neurons need proteins to carry out multitudes of functions in and around the cell and it is estimated that a neuron has nearly millions of proteins. Hence, this cannot be the right option.
Centrioles are cell organelles made of a protein called tubulin. They are necessary for the spindle formation in mitotic cell division.
Nucleus is the control centre of all functions that happen inside the cell. It is found in the soma of the neuron and contains DNA and chromosomes, along with all the necessary information about the cell which is required to carry out various functions. It can be observed as a dark dot when neuron slides are stained and observed under a microscope.
Since neurons do not undergo cell division, the only organelle that they do not require is centrioles.

So, the correct answer is option c. ‘Centrioles’.

Note:
New neurons are formed only in 2 regions of the human brain: a region called the Subventricular Zone (SVN) and the Subgranular Zone (SGZ). Neurons are not replaceable if they die. Neurons can die because of a variety of reasons, such as a stroke, concussion or in the case neurodegenerative diseases such as Alzheimer’s.