Prokaryotes Vs. Eukaryotes

Prokaryotes Vs. Eukaryotes

This article on prokaryotes vs. eukaryotes explains the difference between the two major groups of organisms.
All of us have a fair knowledge that every living entity is made up of small building units called cells. Depending upon the complexity of the cellular structures, the cells belong to two different groups, namely, the prokaryotic and eukaryotic cells.

Accordingly, organisms made up of prokaryotic cells are called prokaryotes; while eukaryotes are those having eukaryotic cells. In biology, the comparison between both these organisms is studied in detail to understand the evolution of life on Earth.

Differences between Prokaryotes and Eukaryotes

Prokaryotes are simple and primitive organisms that lack membranous cell organelles. Their opposites are eukaryotes, which are advanced and complex, and have membrane-bound cell organelles.

For a better understanding, the characteristic distinguishing features between both types of organisms are explained below.

Labeled Eukaryotic Cell DiagramLabeled Prokaryote Cell Diagram

Sketch by Abhishek Sharma

Cell Size
The structural simplicity of prokaryotic organisms is related to their small cell size. They have a higher value of surface to volume ratio, thus allowing quicker absorption of nutrients and supplying them to other cellular parts. On the contrary, the same surface to volume ratio is small in eukaryotes, and hence, they require specialized organelles for carrying out different cellular functions.

Nuclear Body
One of the main differentiating points between the two is the presence or absence of membrane-enclosed nuclear body. In prokaryotes, it lacks outer membrane covering and nucleolus, whereas nucleolus is present, and a double layered membrane surrounds the nuclear body in eukaryotes. Referred to as cell nucleus in eukaryotes, such an organelle is called nucleoid in prokaryotes.

Chromosome Content
The nuclear body houses the chromosome in both prokaryotes and eukaryotes. Single in number and circular in shape, the chromosome in prokaryotes is made up of Deoxyribonucleic Acid (DNA) and proteins. Regarding chromosome content in eukaryotes, it is usually more than two in number, and composed of DNA, histone, and other proteins.

The ribosomes are the organelles responsible for synthesis of proteins inside the cell. Generally, they are made up of two subunits. In prokaryotes, the ribosome type is of 70S, and the two subunits are 50S and 30S. Ribosome in eukaryotes is of 80S type, and the two comprising subunits are 60S and 40S.

Other Organelles
As mentioned already, the cell size in prokaryotes is relatively smaller, when compared to that of the eukaryotes. As a consequence, the organelles like mitochondria, golgi bodies, endoplasmic reticulum, and chloroplast are absent in the small-sized prokaryotic cells. Eukaryotes house all these membrane-bound organelles inside their cells.

Cell Division
Cell division in prokaryotes is simple, and is carried out by binary fission method. The parent cell (haploid cell) divides into two equal daughter cells. Eukaryotes have diploid cells, which divide first by mitosis, and further into two haploid ones by meiosis. The resulting haploid gametes fuse to form a diploid cell.

Let's see the living examples, which represent each group. The most familiar example of prokaryotes is bacteria; while algae and fungi along with all complex plants and animals are eukaryotic in nature. Virus resembles cellular properties of both these groups, hence they are neither prokaryotes nor eukaryotes.

Scientists are of the opinion that prokaryotes are the earliest organisms to exist on earth. After undergoing several changes in organic compounds, the cells got evolved to complex eukaryotic types in due course of time. To be more precise, the first eukaryotes were evolved from existing prokaryotes in those times.

Despite the above mentioned differences, there are many similarities between prokaryotic and eukaryotic cells. For example, both have DNA and chromosomes as genetic materials. After all, both are basic units for survival of life forms.
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