Difference between prokaryotic and eukaryotic cell

We all have heard these terms in our elementary school and almost each of us knows that prokaryotes are pre-existing cells and eukaryotes evolved later. In prokaryotes, the word ‘pro’ means before, and ‘kary’ means the nucleus (in the Greek language). Do you know that prokaryotes were first discovered in the 1940s? And, the first eukaryote appeared almost 1.5 billion years ago. Prokaryotes, on the other hand, have existed for at least 3.5 billion years before and were the first form of life on Earth. Moreover, prokaryotes and eukaryotes have various differences and similarities with respect to their structures. In this article, we will discuss the difference between prokaryotic and eukaryotic cells.

Prokaryotic cell

As I mentioned earlier, ‘pro‘ means before and ‘kary‘ means nucleus. Prokaryotic cells are unicellular, small cells that lack membrane-bound organelles. These primitive cells have a nucleoid and typically consists of a single large loop called a circular chromosome but lack a nuclear membrane. As a result, their genetic material freely moves within the cell. The two most common shapes of the prokaryotic cell are cocci and rods. Although, Procaryotes vary in size as much as in shape.

Prokaryotic cells usually are bounded by a chemically complex cell wall, which covers the plasma membrane. The plasma membrane in turn surrounds the cytoplasm and its contents. Because most prokaryotic cells do not contain internal, membrane-bound organelles, their interior appears morphologically simple.

The Nucleoid region contains their genetic material and is usually not separated from the surrounding cytoplasm by membranes. Many prokaryotes use flagella for locomotion. In addition, many are surrounded by a capsule or slime layer external to the cell wall.

Eukaryotic cell

In the term eukaryotes, ‘Eu‘ means true and ‘kary‘ means nucleus. Thus, eukaryotes are cells that have a true membrane-bound nucleus. Eukaryotes are more complex and much larger than the prokaryotes. They also show better structural organisation and increased functional efficiency than prokaryotes. They include almost all the major kingdoms except kingdom monera.

Eukaryotic cells can be unicellular or multicellular. In unicellular eukaryotes, the single-cell performs all the activities including response to the environment, capturing of food, ejection of excess fluid, evading the predators, etc.

In multicellular eukaryotic cells, different types of specialized cells carry out different functions. They have an advantage over unicellular eukaryotic cells as there is a division of labor among the cells of multicellular organisms. For example, disc-shaped RBCs (red blood cells) help in the transport of oxygen.

Difference between prokaryotic and eukaryotic cell

The presence of the eukaryotic nucleus is the most apparent difference between these two cell types, but many other major distinctions exist. Prokaryotic cells are much simpler structurally. In particular, an extensive and diverse collection of membrane-delimited organelles is missing. Furthermore, prokaryotes are functionally simpler in several ways. They lack mitosis and meiosis and have a simpler genetic organization. The main key differences between prokaryotic and eukaryotic cells are given below:

1. Size

A prokaryotic cell is generally smaller (1-10µm) whereas eukaryotic cell is larger (5-100µm).

2. Genetic material

In prokaryotic cells, the genetic material is in the form of a large, circular molecule of DNA while in eukaryotic cells, the nuclear DNA is linear and tightly bound to special proteins known as histones, forming a number of more complex chromosomes.

3. Nucleus

A true nucleus is absent in prokaryotes whereas it is present in eukaryotes. Instead, prokaryotes have a nucleoid region. The nucleoid serves their genetic material. It is an irregularly shaped region that contains the cell’s DNA. Moreover, it is not surrounded by a nuclear membrane. On the other hand, the eukaryotic nucleus has a nuclear membrane.

4. Chromosome number

Prokaryotes have single chromosomes. On the other hand, eukaryotes have multiple chromosomes.

5. Membrane-bound organelles

These are absent in prokaryotes. On the contrary, various membrane-bound organelles are present in eukaryotes such as mitochondria, chloroplast, Golgi, ER, etc.

6. Mesosomes

Mesosomes are present in prokaryotes whereas absent in eukaryotes.

7. Ribosomes

A prokaryotic ribosome is 70S (50S+30S) while eukaryotic ribosome is 80S (60S+40S). Moreover, prokaryotes haves generally have smaller ribosomes as compared to eukaryotes. If I talk about the shape, the prokaryotic ribosome is spherical and the eukaryotic ribosome is linear.

8. Cell wall

In prokaryotes, the cell wall is non-cellulosic and it comprises of peptidoglycan. On the other hand, it is cellulosic in eukaryotes.

9. Cytoplasmic streaming

It is the movement of the fluid substance (cytoplasm) within a plant or an animal cell. Unlike prokaryotes, it is present in eukaryotes.

10. Energy metabolism

Mitochondria are absent hence, oxidative enzymes are bound to the plasma membrane in case of prokaryotes. On the other hand, mitochondria are present in eukaryotes and oxidative enzymes are packaged within it.

11. Mode of reproduction

Prokaryotic cell reproduces asexually whereas eukaryotic cells have both asexual and sexual mode of reproduction. Further, the prokaryotic cell divides by fission or budding whereas mitosis or meiosis occurs in eukaryotes.

12. Organelles

These organelles are only present in eukaryotes otherwise absent in prokaryotes:

1. Endoplasmic reticulum
2. Lysosomes and centrosomes
3. Mitochondria
4. Nucleus
5. Cytoskeleton
6. Golgi apparatus
7. Chloroplast
8. Vacuoles

For more information, see also: Cell organelles: structure and function

Difference between prokaryotic and eukaryotic cell table

	Prokaryotes	Eukaryotes
Size	1-10µm smaller in size	5-100µm larger
Genetic material	large, circular	tightly bound, linear
DNA	not found in well-organized chromosomes.	found in well organized chromosomes.
DNA replication	Occurs in cytoplasm	Occurs in the nucleus
Nucleus	absent Instead, they have nucleoid	present
Nuclear membrane	absent	present
Chromosome No.	single chromosome	multiple chromosome
Membrane-bound organelles	absent	present
Mesosomes	present	absent
Ribosomes	70S (50S+30S)	80S (60S+40S)
Ribosome’s location	Free in cytoplasm or bound to cell membrane	Attached to rough endoplasmic reticulum
Cell wall	non-cellulosic	cellulosic
Cytoplasmic streaming	absent	present
Energy metabolism	Mitochondria absent. Hence, oxidative enzymes are bound to the plasma membrane	Mitochondria present. oxidative enzymes are packaged within mitochondria
Reproduction	asexual	both sexual and asexual
Cell division	by fission or budding	by mitosis or meiosis
Endoplasmic reticulum	absent	present
Flagella	smaller in size	larger in size
Plasmids	present	rarely found
Lysosomes and centrosomes	absent	present
Mitochondria	absent	present
Transcription	occurs in cytoplasm	occurs inside the nucleus
Transcription and translation	Occurs simultaneously. It occurs in the cytoplasm.	Transcription occurs in nucleus and then translation occurs in cytoplasm
Cytoskeleton	absent	present
Golgi	absent	present
Chloroplast	absent	present
Vacuoles	absent	present
Examples	Bacteria and Archaea	Protists, Fungi, Plants, and Animals
Metabolic rate	Higher due to larger surface area to volume ratio	Comparatively slow
Endocytosis and exocytosis	It is absent	It is present

Sources and External links

Cell and molecular biology by Prakash S. Lohar, page no. 1-10, 16.

Cell biology: organelle structure and function by David E. Sadava.

Jawetz, Melnick, & Adelberg’s Medical Microbiology, 26th Edition, section>1 chapter no. 2

Esau’s Plant Anatomy; Meristems, Cells, and Tissues of the Plant Body: Their Structure, Function, and Development, Third Edition by RAY F. EVERT, chapter no. 2: prokaryotic and eukaryotic cells.

Lastly, Prescott’s Principles of MICROBIOLOGY by Joanne M. Willey, Linda M. Sherwood and Christopher J. Woolverton, chapter 3 and 4.