Nucleus/ Nuclei
The nucleus is a storehouse
of genes, the brain of cells, and the largest cell organelle. The
nucleus contains genetic material in the form of RNA/DNA, thus playing an
important role in the transmission of genetic material from one organism to
another. It contains hereditary information.
The nucleus stores the cell's hereditary material or genetic
material of the cell (DNA), which contains hereditary units called genes. Its
controls, coordinates, and regulates all cellular activities within and outside
the cell that’s why it is called the control center of the cell.
Eukaryotic cells have a true nucleus, the nucleus is defined
well-organized organelle containing DNA and is surrounded by a nuclear
membrane.
Know here the structure of golgi apparatus and endoplasmic
reticulum.
Structure of Cell Nucleus
Nucleus and Its Parts
The nucleus consists of -
1. Nucleoplasm
2. Nucleolus
3. Nuclear Pore
4. Nuclear Envelope/ Nuclear
Membrane
1. Nucleoplasm
It contains nucleosides (responsible for encoding,
transmitting, and expressing genetic information), nucleotides (building
blocks of nucleic acid; DNA and RNA), enzymes, nucleoprotein (protein
associated with nucleic acids), and minerals, etc.
The nucleus stores chromatin (DNA and proteins) in a
gel-like substance called, nucleoplasm. Chromatin is a substance within a
chromosome consisting of DNA (deoxyribonucleic acid) and protein.
Chromatin contains most of the cellular DNA, in association with
basic histone protein. Histone is a protein that provides structural support to
a chromosome, giving a more compact shape to the chromosome.
2. Nucleolus
The spherical nucleolus is an organelle, a condensed region of
chromatin in the nucleus, plays a key role in the transcription (DNA into
RNA) and occurs processing of ribosomal RNA (rRNA).
Nucleoli or nucleolus are rich in RNA (Ribonucleic acid), aggregation
of protein (construction of ribosome), RNA, and DNA. The nucleolus is a site
where ribosome
synthesis occurs.
The nucleolus's primary function is ribosomal RNA (rRNA) synthesis
and ribosome biogenesis.
The nucleolus disappears during cell division. During cell
division, the chromatin is organized into a small thread-like structure called a chromosome. The human somatic cell (cell except for sperm and egg cell) contains
23 pairs of chromosomes. The egg and sperm cells have only 23 chromosomes each.
3. Nuclear Pore
A nuclear envelope or nuclear membrane contains many minute
opening called nuclear pore which allows the exchange of material between the nucleus and cytoplasm.
Nuclear Pore connects
the nucleoplasm (nucleus) with the cytoplasm.
4. Nuclear Envelope
It is a bilayered membrane separated by perinuclear space,
bound the nucleus from outside, and separates the nucleus from the cytoplasm. The
outer layer is connected with the endoplasmic reticulum.
Functions of Nucleus
Key functions are-
1. Nucleus controls
and regulates the activities of the cell, it controls the metabolic
activities of cells.
2. It carries the
genes that contain the hereditary information and controls gene expression and
mediates the replication of DNA during the cell cycle.
3. It controls and
coordinates the direct many cellular structures, and cell activities, which include
growth, metabolism, protein synthesis, and reproduction (cell division)
mean it controls cell division. So, it is called the brain
of cells.
4. It contains
genetic material in the form of DNA/ RNA and plays an important role in
transmission (transferring).
5. All the RNA;
messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA) needed for
the cell because they are directly involved in protein synthesis are synthesized
in the nucleus. Without a nucleus, a cell can neither survive, nor show
specialized activity.
6. It is the
control center of the cells.
7. It controls
replication (DNA Synthesis), transcription( RNA Synthesis), and translation
(protein synthesis).
8. DNA and RNA polymerase
enzymes are markers of the nucleus.
9. It is involved in
the production of various enzymes.
Check out here what is centrosome
and centriole.
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