Difference Between Nucleus and Nucleolus

The key difference between nucleus and nucleolus is that nucleus is the most important cell organelle that houses the genetic material of a eukaryotic cell while nucleolus is a sub-organelle located inside the nucleus that contains RNA.

The cell is the building block of all the living organisms. There are various components of a cell. A eukaryotic cell has membrane-bound cell organelles. Each cell organelle has a unique function to carry out. Thus, cell organelles perform different functions that are vital for the survival of a cell. The nucleus is the main and most important cell organelle of a eukaryotic cell. It is the location where the genetic material resides in eukaryotic cells. The nucleolus is an area inside the nucleus that contains RNA.

CONTENTS

1. Overview and Key Difference
2. What is Nucleus 
3. What is Nucleolus
4. Similarities Between Nucleus and Nucleolus
5. Side by Side Comparison – Nucleus vs Nucleolus in Tabular Form
6. Summary

What is Nucleus?

Nucleus is a membrane-bound organelle present in almost every eukaryotic cell except some cells such as red blood cells. Nucleus is the largest organelle in animal cells. It is mostly round shaped. Also, this is one of the essential organelles in a cell. Moreover, the structure of the nuclear membrane is similar to the structure of the plasma membrane. The outer nuclear envelope joins the rough endoplasmic reticulum and may have ribosomes on it. Nuclear envelop is discontinuous and consists of spaces known as pores. They occupy proteins, which act as trans-membrane channels. Furthermore, the nuclear envelope separates the content inside the nucleus from the cytoplasm and other organelles.

There is a viscous liquid known as the nucleoplasm inside the nucleus. Nucleoplasm is very similar to the cytoplasm. Majority of cells houses the genetic material of an organism inside the nucleus. DNA molecules, which are responsible for controlling the cell and inheriting genes, are arranged into chromosomes inside the nucleus. During nuclear division, the nucleus undergoes four phases: prophase, metaphase, anaphase and telophase. During these phases, the nucleus of a cell undergoes changes, and ultimately divides into two (in mitosis) or four (in meiosis) daughter nuclei.

What is Nucleolus?

Nucleolus is a structure found within the nucleus. It is a highly dense area of the nucleus, which occupies 25% of the total volume of the nucleus. Moreover, there are three distinct regions of the nucleolus: fibrillar centres, dense fibrillar component, and granular component.

Moreover, the nucleolus is a sub-organelle that is non-membranous. It consists of DNA units that are responsible for coding rRNA for ribosome production. Therefore, the main function of nucleolus is to synthesize rRNA and produce ribosomes (ribosome biogenesis).

What are the Similarities Between Nucleus and Nucleolus?

• Nucleus and nucleolus are two components of the eukaryotic cell.
• In fact, nucleolus is a part of the nucleus.
• And, both contain nucleic acids.
• Moreover, they are important for protein and RNA production.

What is the Difference Between Nucleus and Nucleolus?

Nucleus is an important cell organelle that houses the genetic material of a eukaryotic organism while nucleolus is a part of the nucleus which contains RNA and carries out ribosome biogenesis. So, this is the key difference between nucleus and nucleolus. Thus, nucleolus is a sub-organelle, whereas nucleus is the main organelle within a cell.

Moreover, a further difference between nucleus and nucleolus is that nucleus is a double membranous organelle whereas nucleolus doesn’t have any membrane. Furthermore, there is also a functional difference between nucleus and nucleolus. The main function of the nucleus is to control cellular activities and regulate gene expression while the main function of nucleolus is to produce ribosomes. Besides, nucleus is mainly responsible for producing mRNA while nucleolus is mainly responsible for producing rRNA.

Summary – Nucleus vs Nucleolus

In summary of the difference between nucleus and nucleolus, the nucleus is the main cell organelle of a eukaryotic cell. It houses the genetic material of an organism. Meanwhile, nucleolus is a part of the nucleus; it is a dense area of the nucleus. Moreover, it is a sub-organelle. Nucleolus is responsible for producing rRNA and ribosomes. Thus, it is rich in RNA while nucleus is rich in DNA. Moreover, nuclear envelope surrounds the nucleus while nucleolus is non-membranous.

Reference:

1. “Nucleus and Ribosomes.” Khan Academy, Available here.
2. Lam, Yun Wah, et al. “The Nucleolus.” Journal of Cell Science, The Company of Biologists Ltd, 1 Apr. 2005, Available here.

Image Courtesy:

1. “0312 Animal Cell and Components” By OpenStax – (CC BY 4.0) via Commons Wikimedia
2. “0318 Nucleus” By OpenStax –  (CC BY 4.0) via Commons Wikimedia