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The nucleus is a membrane bound organelle found only in eukaryotic cells. However, it is not to be confused with nucleoid, a non-membrane bound genetic materials found in prokaryotes.

Structure of the nucleus

The nucleus of eukaryotic cells is made up of the following:

  1. Nuclear envelope
  2. Nucleoplasm
  3. Nuclear lamina

Nuclear envelope

This is also known as the membrane that encloses the cell nucleic acid. It contains an opening known as nuclear pore, a selective barrier that prevents the inward and outward movement of macromolecules in and out of the nucleoplasm. Nucleoporin, a protein family helps to transport these molecules in and out of the nucleoplasm.


This is similar to the cytoplasm in living cells. It is the portion of the nucleus where chromosomes and nucleolus are found.


Nucleoplasm = Chromosomes and nucleolus.

  • Chromosomes

Chromosomes are structures in the nucleoplasm composed of chromatins, that carries the genetic information of the cells as well as the protein called histone.


Chromosome = Genetic material (DNA/RNA) and histones

  • Nucleolus

This is the site of rRNA synthesis and ribosome assembly in the nucleus.


Nucleolus = rRNA synthesis and ribosomes

Nuclear lamina

This is a network of intermediate filaments called lamins, that protect and give the nucleus it mechanical support.

Functions of the nucleus

  • The nucleus protects the genetic information in the cells that can be transferred from one generation to another
  • It allows the expression of gene coded in it through the process of transcription and translation.
  • It is also the site of RNA and ribosome synthesis.


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