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Biology > Cell the Unit of Life > Nucleus – Definition, Structure & Function (with Diagram)
Cell the Unit of Life

Nucleus – Definition, Structure & Function (with Diagram)

Nucleus Diagram

The nucleus is a term that we often find in Biology. It is a special structure found in almost all cells. A nucleus diagram is very useful to properly understand it.

It is not present in bacteria and blue-green algae. Since it is found inside a cell, it is very small. Let’s find out more about the nucleus.

Nucleus Definition

The nucleus is an organelle that is present in most eukaryotic cells. However, the exception is blood cells.

Furthermore, in animal cells, it is the hardest and largest organelle. We can identify it easily with the help of light microscopy.

Also, the average mammalian nucleus occupies around 10 per cent of the total volume. It is a membrane-bound organelle which contains genetic material.

nucleus diagram

Nucleus Structure 

The nucleus is the command centre of a cell. This is because it contains the genetic material of the cell. Therefore, it consists of a number of structural elements which facilitate its functions.

The nucleus of a cell has a spherical shape. A nucleus diagram is very useful for studying its structure. Its structure consists of the following important parts:

The nuclear membrane- This is an aspect of the nucleus that differentiates eukaryotic cells from prokaryotic cells. Furthermore, it is a structure of double layers. Moreover, it contains phospholipids.

This forms the lipid bilayer nucleus envelope. Also, it contains nuclear pores. Nuclear pores are made up of proteins and through them, substances enter and exit the cell.

Nucleoplasm- It is a type of protoplasm. Furthermore, it consists of enzymes, organic molecules, and dissolved salts.

Moreover, it acts as a cushion to protect the nucleolus and chromosomes. Also, it helps maintain its shape.

Nucleolus- This is the most important organelle. It is a dense structure which lacks its own membrane.

Moreover, it breaks up during cell division but then reforms after mitosis. Its size depends upon the level of production of the ribosome.

Its size also depends on the different types of molecular processes.

Chromosomes- These are thread-like structures. Moreover, they are made up of strands of DNA as well as histone proteins.

Further, the main parts of genes consist of kinetochores, telomeres, and chromatids. Genes are tightly packed in here.

Nucleus Function 

Nucleus performs many important functions. They are as follows:

  • Nucleus helps in maintaining the security of the genes
  • It controls the functions of the cell by regulating gene expression
  • It controls the hereditary traits of the organism
  • Furthermore, it stores DNA strands and proteins
  • The nucleus is the site of RNA transcription
  • It governs gene expression and also facilitates DNA replication.
  • It also controls the synthesis of enzymes.

Solved Question for You

Q1 What are the thread-like structures in a nucleus?

a. Nuclear membrane

b. Chromosomes

c. Nucleoplasm

d. Nucleolus

A1 The correct answer is option B. Chromosomes are thread-like structures. They are made up of strands of DNA as well as histone proteins.

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