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The nucleus has four components:

1. Nuclear membrane: It is the outer covering of nucleus. It separates
the nucleus from cytoplasm. It contains many pores and exchange of
materials between cytoplasm and nucleus takes place through these

pores.
2. Nucleoplasm: The fluid or jelly like substance present inside nucleus
is called nucleoplasm. The chromatin material or Chromosomes and
nucleolus are present in it.

3. Nucleolus: It is a solid spherical mass present in the nucleus. It
synthesizes ribosomes and plays an important role in protein
synthesis.

4. Chromosomes: These are thread-like structures. Chromosomes
contains genes and genes transfer characters from parents to
offspring. Genes are the units of inheritance.

Functions: Nucleus is the brain of a cell. It controls all activities of the cell.
It plays an important role in cell division. It helps in transmission of
characters from parents to offspring.

Types: On the basis of organisation of nucleus, the cells are of two types -

1. Prokaryotic cells: The nuclear material is present without having
nuclear membrane. The nuclear material is present in cytoplasm
known as nucleoids. The number of chromosomeis one. These are

primitive cell and the size of cells ranges from 0.1 to 5 microns.The
organisms having prokaryotic cells are called prokaryotes and all
prokaryotes are unicellular. Examples-Bacteria, Blue-green algae.

2. Eukaryotic cells: The nuclear material is present within the nuclear
membrane. The nucleus is well organized. The number of
chromosome is one. These are advanced cells and the size of cells
ranges from 10 to 100 microns.The organisms having eukaryotic cells

are called eukaryotes and eukaryotes may be unicellular or
multicellular. Examples-plant cells, animal cells.