Nucleus-Definition, Structure, Parts, Functions, Diagram

What is Nucleus?

The hereditary information of the cell is contained inside the membrane-bound nucleus. The nucleus also regulates the cell’s development and reproduction.

The nucleus is the brain of a eukaryotic cell and is often the most prominent organelle, making up around 10% of the volume of the cell.

Typically, a eukaryotic cell includes just one nucleus. Red blood cells (RBCs), for example, are an example of an enucleated eukaryotic cell. On the other hand, slime moulds are an example of a multinucleate eukaryotic cell.

A nuclear membrane separates the nucleus from the cytoplasm or the remainder of the cell.

As it regulates the integrity of genes and gene expression, the nucleus is frequently described as the control centre of a cell.

Nucleus Structure

The nuclear membrane, nucleoplasm, chromosomes, as well as the nucleolus are all structural components of the nucleus.

Nuclear Membrane

  • The nucleus’ contents are contained inside the double-layered nuclear membrane. The endoplasmic reticulum is attached to the outer layer of the membrane.
  • The nuclear membrane is composed of phospholipids that create a bilayer of lipids, much like the cell membrane.
  • The envelope maintains the structure of the nucleus and helps regulate the passage of molecules via nuclear pores. Through a number of holes known as nuclear pores, the nucleus communicates with the cytoplasm and the remainder of the cell.
  • Through these nuclear pores, major molecules (proteins and RNA) are transferred between both the nucleus and the cytoplasm.
  • Between a nuclear membrane’s two layers lies a region filled with fluid called the perinuclear space.


  • Nucleoplasm is the gelatinous substance found inside the nuclear membrane.
  • This semi-aqueous material, also called karyoplasm, resembles cytoplasm in that it contains mostly water with salt content, enzymes, as well as organic molecules drifting inside.
  • Nucleoplasm, which serves to cushion and defend the nucleus’ contents, is located around the nucleolus and chromosomes.Nucleoplasm supports the nucleus and contributes to preserving its shape.
  • In addition, the nucleoplasm facilitates the movement of molecules such as enzymes and nucleotides (DNA and RNA subunits) within the nucleus. Nuclear holes permit material exchange within the cytoplasm and nucleoplasm.


  • The nucleolus is a small, membrane-free structure located within the nucleus that is made up of RNA and proteins.
  • Up to four nucleoli may be found in the nucleus of certain eukaryotic species.
  • Nucleolar organisers, which are chromosomal areas that carry the genes for ribosome synthesis, are located in the nucleolus. The nucleolus facilitates the production of ribosomes by transcribing and assembling ribosomal RNA subunits. In the process of protein synthesis, these pieces are assembled into ribosomes.
  • The nucleolus disappears during cell division and returns after cell division is complete.


  • The organelle that contains chromosomes is called the nucleus.
  • Cell DNA, which makes up chromosomes, is responsible for conveying genetic data and sending cell development directions, growth, and reproduction.
  • Histones, a kind of protein molecule, and DNA strings, together known as chromatin, make up chromosomes.
  • While the chromosomes are arranged into lengthy, while a cell is “resting,” or not dividing, it consists of chromatin structures.
  • Chromatin is subdivided into heterochromatin and euchromatin based on its activities. The first kind is a severely compressed, dormant form of transcription that is mostly located near the nuclear membrane. In contrast, euchromatin is a sensitive, less compact arrangement of chromatin that is extensively spread across a cell that is transcribing.

The nucleus also houses a number of additional non-membrane-delineated structures in addition to the nucleolus. These include paraspeckles, splicing speckles, promyelocytic leukaemia (PML) bodies, polymorphic interphase karyosome association (PIKA), Cajal bodies, and Gemini of coiled bodies.

Nucleus Functions

The nucleus offers a place for genetic transcription that is distinct from the cytoplasmic site of translation, enabling degrees of gene control not possible in prokaryotes. The primary roles of the cell nucleus throughout the cell cycle are to regulate gene expression and conduct DNA replication.

  • It regulates an organism’s inherited features.
  • Additionally, the organelle is in charge of cell proliferation, differentiation, and protein synthesis.
  • Chromatin is the name for the structure that stores genetic material, or genes, as long, thin strands of DNA (deoxyribonucleic acid).
  • The nucleolus is where RNA (ribonucleic acid) and proteins are kept.
  • Messenger RNA (mRNA) is synthesised for protein synthesis at a transcription site in the nucleus.
  • Chromatins are organised into chromosomes in the nucleus during cell division.
  • The nucleolus produces ribosomes, which are protein manufacturers.
  • Selective movement of energy molecules and regulatory elements via nuclear pores

Nucleus FAQs

Where can you find the nucleus?

The cell’s nucleus is located in the middle.

Where can you find a nucleolus?

Within the nucleus is the nucleolus.


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