Who Discovered Nucleus Get complete PDF

Robert Brown (1881) discovered the nucleus.
J. Hammerling (1953) proved the hereditary role of the nucleus on a green alga Acetabularia

1. Who Discovered Nucleus
Cell ( Class 9)
NUCLEUS
1.The nucleus is a small, round, and membrane-bound structure found in cells.
2.And the fluid inside the nucleus surrounded by the nuclear membrane is called
nucleoplasm.
3.It controls the cell's growth and reproduction as it contains the cell's hereditary
information.
4.It's covered by a dual layer called a nuclear membrane.
5.It's the most important part of the cell that controls and regulates all its vital
activities.
Robert Brown(1881) discovered the nucleus.

2. J. Hammerling (1953) proved the hereditary role of the nucleus on a green alga
Acetabularia
●Distribution: Present in all eukaryotic cells. In certain cells, they get disintegrated
when cells attain maturity e.g., RBC in mammals, no true nucleus is present in
prokaryotes.
●Number: Generally a cell contains a single nucleus i.e., mononucleated
condition, sometimes certain cells show binucleated or multinucleated conditions
●Shape: The shape of the nucleus is variable and the shape depends on the
functional state of the cell. The shape may be discoid in the case of flattened
squamous epithelium cells, spherical, cuboidal, or polyhedral cells, ovoid in
columnar cells, bilobed or multilobed in leucocytes.
Position of Nucleus
Structure of aNucleus
Nucleus has the following important parts:
●Nuclear membrane
●Nucleoplasm

3. Flow chart of Nucleus showing its constituents
Nuclear Membrane
●The nucleus is bounded by a double membrane structure called nuclear
envelope or karyotheca.
●Nuclear membrane is semi-permeable and helps exchange dissolved matter
between protoplasm and nucleus while nuclear pores are the pathway for the
exchange of micromolecules.
●It is a thin double membrane surrounding the nucleus. Each membrane is 90 Å
thick and both are separated by a 120-300 Å, this space is known as perinuclear
space. It contains many small nuclear pores of 400 Å diameter. They are
surrounded by a thin membrane and protoplasmic Annulus.
●Inside the nucleus, a clear or slightly acidophilic mass is present, which is called
karyoplasm or nuclear sap.
Nucleoplasm
●It is a transparent, homogeneous, and granular dense fluid. It possesses high
quantities of phosphorous and proteins.
●Many thread-like structures are irregularly present in the nucleoplasm. Their
shape changes during cell division.
It has the following structures in it:
●Nuclear chromatin
●Nucleolus
Nuclear Chromatin Or Chromatin Material
●The nucleoplasm contains many thread-like, coiled, and many elongated
structures known as Nuclear reticulum and is made up of chromatin, it is also
known as chromatin net.

4. ●These thread-like structures contain small granular bodies known as
chromomeres. At the time of cell division chromatin, net thickens and
distinguishes into rod-like structures known as chromosomes.
●Each chromosome remains in the form of a chromatin network but actually
consists of two parts known as Hetero-chromatin and Euchromatin.
●It is made up of two chromonemata and each chromonemata thread contains
numerous small button-shaped particles known as genes.
●They are made up of DNA and help in the transfer of heredity characters from
one generation to another.
Cells Position
Embryonic cells Central position
Adipose tissue Peripheral position
Glandular cells Basal position
Mature plant cell Peripheral etc.

5. Nucleolus
●The nucleus contains a large, spherical, dense, granular, and stable structure
known as nucleolus.
●These are one or more round structures that are not bound by a membrane.
●They are rich inRNAand proteins.
●It is known as the factory of ribosomes.
Functions of Nucleus
●Control center: It controls all the metabolic activities of the cell. If it is removed
theprotoplasmdries up and dies.
●Genetic information: It is responsible for the transmission of hereditary traits.
●It regulates the cell cycle.
●Ribosomesare formed by the nucleolar part of thenucleus.
●Nucleus plays a central role in cellular reproduction (the process by which a
single cell divides to form two new cells).
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