Nucleus

Nucleus as a cell organelle was first discovered by Robert Brown as early as 1831. Later, the material of the nucleus stained by the basic dyes was given the name chromatin by Flemming.

The nucleus is a double membrane-bound protoplasmic body containing all the genetic information. That the nucleus is a storehouse of hereditary information was proved by Danish biologist Joachim Hammerling on the basis of his studies in Acetabularia. The interphase nucleus is a nucleus in the non-dividing or metabolic phase.

It is the largest of the cell organelles. It is present in all living eukaryotic cells except mature sieve cells of vascular plants and red blood corpuscles of mammals, which have a nucleus only during the early stages of their development.

• Number-Commonly, cells are uninucleate, that is, they possess a single nucleus. Binucleate cells, e.g., Paramecium, has two nuclei. Multinucleate or poly nucleate cells have many nuclei, e.g., some cells of bone marrow, striated muscles, latex vessels, several fungi, Ascaris, and algae. Multinucleate animal or Protista cells are called syncytial cells, while multinucleate plant and fungal cells are known as coenocytic cells.
• Position-It is found in the region of maximum metabolic activity in the cytoplasm. Commonly, it is situated in the geometric center of the cell. The nucleus is peripheral in fat-storing cells, in plant cells due to the development of a large central vacuole, and basal in glandular cells. In Spirogyra, it is suspended in the central vacuole by cytoplasmic strands.
• Shape-The nuclei are generally round in outline, but they appear oval or elliptical in plant cells having large central vacuoles, disc-shaped nuclei in the cells of squamous epithelium, lobed in white blood corpuscles, and irregularly branched in silk spinning cells of insects.
• Biochemical Analysis. DNA—9-12%. RNA—5%. Lipids—3%. Basic proteins—15%. Acid proteins, neutral proteins, and enzymes—65%. Traces of minerals like Calcium, Magnesium, Potassium, and Sodium. Phosphorus is a constituent of DNA, RNA and acid proteins.

The cell is the basic structural and functional unit of living organisms. In biology, the cell has the same central position as that of an atom in the physical sciences. The bodies of living organisms are made up of microscopic units called cells. Cells have evolved a variety of different lifestyles. Many organisms, such as bacteria (both archaebacteria and eubacteria), protozoa(e.g., amoeba), and yeasts consist of single cells (called unicellular organisms) that have the ability to perform a function like self-replication. More complex organisms, called multicellular organisms, those consists of collections of cells that perform particular functions.

Term cell was discovered by Robert Hook in his book Micrographia. The size of the cell is 10-16 micrometers. The shape of the cell may be polygonal, disc-like amoebic, thread-like, cuboid or irregular, oval, hexagonal, circular, branched, elongated, etc. The cells are too small to be seen with naked eyes. So, it is studied with the help of microscopes.