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What is Cell Made up Of? What is the Structural Organisation of a Cell? - Nucleus

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notes

Nucleus:

  • Nucleus is dense and spherical organelle.
  • Nucleus is bounded by two membranes, both forming nuclear envelope. Nuclear envelope contains many pores known as nuclear pores.
  • The fluid which present inside the nucleus is called nucleoplasm.
  • Nucleus contains chromosomes and chromosomes containing genes which are the centres of genetic information.

The nucleus contains chromosomes, which are visible as rod-shaped structures only when the cell is about to divide. Chromosomes contain information for inheritance of characters from parents to next generation in the form of DNA (Deoxyribo Nucleic Acid) molecules.

Chromosomes are composed of DNA and protein. DNA molecules contain the information necessary for constructing and organising cells. Functional segments of DNA are called genes.

In a cell which is not dividing, this DNA is present as part of chromatin material. Chromatin material is visible as entangled mass of thread like structures. Whenever the cell is about to divide, the chromatin material gets organised into chromosomes.

The nucleus plays a central role in cellular reproduction, the process by which a single cell divides and forms two new cells. It also plays a crucial part, along with the environment, in determining the way the cell will develop and what form it will exhibit at maturity, by directing the chemical activities of the cell.

In some organisms like bacteria, the nuclear region of the cell may be poorly defined due to the absence of a nuclear membrane. Such an undefined nuclear region containing only nucleic acids is called a nucleoid.

Functions:

  • Nucleus controls all the metabolic activities of the cell.

  • It regulates the cell cycle.

  • Nucleus is the storehouse of genes. It is concerned with the transmission of hereditary traits from the parent to offspring.

Shaalaa.com | Structure of cell - Nucleus

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