Question

Functions of the cell is controlled by
(a) Protoplasm
(b) Cytoplasm
(c) Nucleolus
(d) Nucleus

Answer 1

Hint: It is also known as the director of the cell. It is the most important cell organelle. It is surrounded by membranes and plays a major role at the time of cell division.

Complete answer:
The nucleus controls all the functions of the cell. It directs various cellular functions.

- Nucleus was first observed by Antony van Leeuwenhoek.
- Nucleus was first described by Robert Brown in 1831 A.D., in orchid cells.
- In plants, the nucleus is eccentric due to the presence of a large vacuole.
- When no nucleus is present in the cell then the cell is called anucleate.
- When two cells are present then such a condition is called binucleate, like in paramecium.
- When more than two nuclei are present in the cell then such a cell is called multinucleate, like in Opalina.
- The cytoplasm is a semi- solid substance of the cell outside of the nuclear membrane of the cell.
- Kidney shaped nucleus is present in Paramecium.
- Chemically the nucleus is composed of of- DNA, RNA, lipids, polymerase enzyme, and minerals like Ca²⁺, Mg²⁺, Na^+, and K⁺.
- Under the electron microscope, the nucleus is seen to be formed of four components- nuclear membrane, nucleoplasm, nucleolus, and nuclear chromatin.
So, the correct answer is,’ Nucleus’.

Note: Nucleus is present in all eukaryotes except mature mammalian RBCs, sieve- tube cells of the phloem, tracheids, and vessels of xylem. It is generally located at the center of the cell.