Function of Nucleus

Nucleus

It is popularly called 'brain of cell'. It is composed of a double layered covering called nuclear membrane.

It has numerous pores called nuclear pores for the transfer of materials from inside the nucleus to cytoplasm.

The nucleus contains 'chromosomes', which are visible as rod shaped structures only when the cell is about to divide.

It encloses a liquid ground substance called nucleoplasm, which contains nucleolus and chromatin material.

In Animal cells, nucleus lies at the centre of the cell whereas in Plant cells, it is present at the periphery of the cell due to presence of a large vacuole. The nucleus consists of the following four parts:

Nuclear membrane : Nucleus is separated from the cytoplasm by a membrane called nuclear membrane. This membrane is also porous and allows the movement of certain selected materials between the cytoplasm and the nucleus.

Nucleoplasm: The dense fluid present in the nucleus is called nucleoplasm.

Chromatin: Some fine, thread like structures, composed of deoxy-ribonucleic acid (DNA) are suspended in the nucleoplasm. These are called chromatin fibres. It is an entangled network of long, thread like structure which condenses to form chromosomes during cell division. In the dividing nucleus, these chromatin fibres condense and form chromosomes. Due to this, chromosomes are only visible in dividing cells. These Chromosomes contain information for the inheritance of features from parents to next generation in the form of DNA molecules (Deoxyribonucleic Acid).

They are composed of two components: i.e. DNA and protein. The DNA molecules contain information necessary for constructing and organizing cells. The functional segments of DNA are called 'genes'. Genes contains genetic codes which are responsible for the unique physical character of an animal or a plant. A child receives one copy of each gene from the mother and another copy of same gene from the father.

Nucleolus : It is a small spherical body present inside the nucleus. It is rich in RNA (Ribo Nucleic Acid). It is a naked irregular structure which is attached to the chromatin. It is spheroidal organelle inside the nucleus. It is the densest organelle and is prominent in cells that synthesize proteins. The number of nucleoli in a cell may be one to several thousand. It contains DNA which synthesizes ribosomal RNA.

Functions of Nucleus:

Nucleus plays an important role in cellular reproduction in which a cell divides to from two new cells.

It also determines the cell development and maturity by directing the chemical activities of the cell.

It helps in the transmission of heredity traits from parents to offspring.

It controls all metabolic activities of cell and if it is removed, the protoplasm dries up.

In some organisms like bacteria, the nuclear region of the cell is poorly defined because of the absence of nuclear membrane. The nuclear region in these organisms contains only nucleic acid. Such an undefined nuclear region is called nucleoid.

Organisms whose cells lack a nuclear membrane are called prokaryotes(means primitive nucleus). They also lack cytoplasmic organelles. Most functions are thus performed by poorly developed parts of cytoplasm. The organisms having a well defined nucleus enclosed in nuclear membrane are called 'eukaryotes'. Eukaryotic cells are further categorized into Plant Cell and Animal Cell.