Nucleus

Nature and occurrence:

• Nucleus is an important component of the cell.
• It acts as control centre of activities of the cell hence it is also known as Brain of the Cell.
• It is spherical organelle located in the centre of the cell in animal cells.
• In plants, it is pushed towards the side of the cell.
• In some cells, it maybe oval irregular or lobed as in case of white blood cells.

Structure:

• It is composed of various parts. They are: nuclear membrane, nucleopore, nucleolus, nucleoplasm, and chromosomes or chromatin.

Nuclear membrane:

• It is a double membrane structure which separates nuclear material from cytoplasm.
• It is also associated with the system of other membrane bound tubules like that of endoplasmic reticulum.
• It serves as a barrier between nucleus and cytoplasm.

Nucleopore:

• Nuclear membrane is discontinuous due to which pores are formed in between and these pores are known as nucleopore.
• These pore allow the transfer of material between the nucleoplasm and cytoplasm.

Nucleolus:

• A smaller spherical body in the nucleus which is devoid of any membrane.
• It is a region where RNA and proteins are richly present.
• It is also involved in the formation of ribosomes.

Nucleoplasm:

• The jelly like substance filled in nucleus.

Chromosomes:

• Chromosomes appear as rod shaped structures during cell division.

• They carry genes and help in inheritance or transfer of characters from the parents to the offspring.
• Gene is a functional unit of inheritance in living organisms which is made up of DNA (Deoxyribo Nucleic Acid) and proteins.
• DNA is made up of small units called nucleotides which are made up of sugar, phosphate and base.
• It carries information necessary for constructing and organizing cell.
• Genes controls the transfer of hereditary characteristic from parents to offspring.
• In a non dividing cell, chromosome appears as a mass of entangled thread which is known as chromatin.

Nucleus in prokaryotes:

• In prokaryotes, nucleus with developed membrane is absent rather chromosome is present in a region called as nucleoid.
• Such cells also lack membrane bound organelles.

Function:

• It controls all the metabolic activities of the cell.
• It regulates the cell cycle that means it controls the rate of cell division.
• It contain genes thus helps in transferring information from one generation to the next.