difference between prokaryotic and eukaryotic cells essay

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Prokaryotic vs Eukaryotic Cells – Similarities and Differences

Prokaryotic and eukaryotic cells are the basic units of life on Earth. The basic distinction between prokaryotes and eukaryotes is that prokaryotes lack a membrane-bound nucleus and organelles. Instead, genetic material and processes occur within prokaryotic cytoplasm. Both prokaryotic and eukaryotic cells contain cytoplasm that is enclosed by a cell membrane. Both perform protein synthesis using ribosomes.

Prokaryotes

Prokaryotes are unicellular organisms that lack membrane-bound structures, including the nucleus and other organelles. Usually, prokaryotic cells are small and relatively simple in structure compared with eukaryotic cells. Prokaryotes have a single, often circular chromosome that occupies the nucleoid region of the cell. Plasmids carry additional DNA .

Here are key prokaryote features:

• Capsule : layer of carbohydrates that surrounds the cell wall of some bacteria and helps them attach to surfaces
• Cell wall : consists of peptidoglycans that give the cell structure and protection
• Cell membrane : also known as the plasma membrane, which encloses the cytoplasm and separates the cell from the environment
• Cytoplasm : region enclosed by the cell membrane
• Nucleoid : region that contains DNA
• Plasmids : independently reproducing DNA
• Ribosome : performs protein synthesis
• Flagella : thin, tail-like structures that aid movement
• Pili : short, rod-shaped structures involves in attachment to surfaces and DNA transfer
• Fimbriae : thin, hair-like structures used for attachment
• Vesicles : sacs released by the membrane that perform a variety of functions
• Vacuoles : storage sacs found in some bacterial cells

A eukaryotic cell has a true nucleus and membrane-bound organelles . Plant and animal cells are examples of eukaryotic cells. Here are key eukaryote features.

• Nucleus : contains DNA and oversees all cell processes
• Nucleolus : site of ribosome biogenesis; plays role in cell stress response
• Plasma membrane : encloses the cell
• Cytoplasm : region between the nuclear membrane and the plasma membrane
• Cell wall : supports and protects plant, algae, and and fungi cells
• Mitochondria : provide chemical energy to the cell in the form of ATP
• Chloroplasts : traps energy for photosynthesis in some eukaryotic cells
• Ribosomes : perform protein synthesis
• Endoplasmic reticulum : makes and modifies proteins (rough); expresses lipids (smooth)
• Golgi apparatus : sorts, packages, and processes proteins
• Vesicles and vacuoles : membrane-bound storage and transportation sacs

Similarities Between Prokaryotic and Eukaryotic Cells

The most important similarity between prokaryotes and eukaryotes is that they both consist of cells. The lipid bilayer that forms the cell membrane separates the molecular machinery of life from the outside environment, while allowing for transport into and out of the cell. Also, both prokaryotic and eukaryotic cells use 2′-deoxyribonucleic acid (DNA) to code for genes.

• Have cell or plasma membrane
• Contain cytoplasm
• Have ribosomes
• Have vesicles
• Have vacuoles

Differences Between Prokaryotic and Eukaryotic Cells

The identifying difference between prokaryotic and eukaryotic cells is the absence or presence of a membrane-bound nucleus and organelles. However, they also differ in size, complexity, reproduction, and means of locomotion.

• Prokaryote cells lack a membrane-bound nucleus or organelles.
• Prokaryotic cells generally are smaller than eukaryotic cells.
• Eukaryotic cells are more complex.
• Prokaryotic cells are unicellular, while eukaryotic cells may be multicellular.
• A prokaryotic cell has a single haploid (n) chromosome, while eukaryotes have multiple, paired, diploid (2n) chromosomes.
• Both types of cells have ribosomes, but eukaryotic ribosomes are larger.
• Prokaryotic chromosomes are circular or linear. Eukaryotic chromosomes are linear and associated with histone proteins.
• Both types of cells may use flagella, but the composition and structure differs between prokaryotic and eukaryotic cells.
• Both types of cells use asexual and sexual reproduction, but sexual reproduction is more common in eukaryotes.
• Plants and fungi are eukaryotes that have cell walls, but they are chemically simpler than prokaryotic cell walls.

Kingdoms of Life

Learn how prokaryotic and eukaryotic cells relate to the kingdoms of life.

Which Came First?

Cells started forming on Earth at least 3.5 billion years ago. These cells were prokaryotes, but much simpler than prokaryotic cells today. Scientists believe eukaryotes arose from symbiosis between prokaryotic cells. Eventually, an ancestral prokaryote endosymbiosed other cells, which became mitochondria and chloroplasts, The origin of other organelles is less clear.

Prokaryotes vs Eukaryotes Worksheet

This worksheets tests whether you recognize the differences between prokaryotes and eukaryotes, including properties of the cells and representative organisms.

Worksheet [ PDF ][ PNG ]

Answer Key [ PDF ][ PNG ]

• Campbell, N.A.; Williamson B,; Heyden, R.J. (2006). Biology: Exploring Life . Boston, Massachusetts: Pearson Prentice Hall. ISBN 9780132508827.
• Gribaldo, S.; Brochier-Armanet, C. (January 2020). “Evolutionary relationships between archaea and eukaryotes”. Nature Ecology & Evolution . 4 (1): 20–21. doi: 10.1038/s41559-019-1073-1
• Maton, A. (1997). Cells: Building Blocks of Life . New Jersey: Prentice Hall. ISBN 9780134234762.
• Nelson, D.L.; Cox, M.M. (2005). Lehninger Principles of Biochemistry (4th ed.). New York: W.H. Freeman. ISBN 978-0-7167-4339-2.
• Raven, P.H.; Johnson, G.B. (2002). Biology . McGraw-Hill Education. ISBN 9780071122610.

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Eukaryotic and Prokaryotic Cells: Key Differences Essay

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Introduction

Differences between the different kingdoms of species might seem obvious at the surface level, yet, inspecting the subject matter closer, one will realize that the line between the two can be drawn at the cellular level. Furthermore, upon the analysis of the differences between eukaryotic and prokaryotic cells, one can develop a proper understanding of the environment that is required for the correct functioning of eukaryotic and prokaryotic cells. Thus, a comparison between the two is required to show that there are two distinct groups of organisms that require different environments and conditions.

The presence of a nucleus is the core difference between eukaryotic and prokaryotic cells, which is even coded in the names thereof. In addition, unlike a eukaryotic cell, a prokaryotic one does not have chromosomes but, instead, contains a substitute called plasmids (Kelly and Callegari 4977). Unlike a chromosome, a plasmid does not have a protein membrane and typically takes a linear shape (Kelly and Callegari 4979). Therefore, the complexity of prokaryotic cells is significantly lower than the one of prokaryotic ones.

In addition, the cellular structure of the two types of cells serves as an important distinction. Prokaryotic cells are typically unicellular, whereas eukaryotic ones are multicellular. The described difference leads to another point of comparison, which is the kingdom that the identified types of cells represent. While prokaryotes typically occur in Bacteria and Archaea, eukaryotic cells can be found in Animals and Plants (“Chapter 4 – Cell Structure”). Thus, a prokaryotic cell can be defined as a simpler life form compared to a more complex eukaryotic one.

Finally, the components that constitute each type of cell are very different, both in their functions and form. It should be noted that there are several organelles that are common for both prokaryotic and eukaryotic cells. However, eukaryotic cells, as more complex mechanisms, contain the organelles that cannot be found in simpler prokaryotic structures. For example, prokaryotic cells do not have lysosomes and peroxisomes, which play the role of conserving and transporting energy and are an important component of eukaryotic cells (“Chapter 4 – Cell Structure”). Similarly, mitochondria and endoplasmic reticulum are not found in prokaryotic cells. Overall, the structure of a prokaryotic cell is less complex than the one of a eukaryotic one.

The DNA as a crucial element in the composition of both prokaryotic and eukaryotic cells also deserves a more detailed analysis as another critical point of difference between the two cell types. In contrast to eukaryotic cells, in prokaryotic ones, the DNA structure is linear due to the arrangement of organelles and, consequently, chromosomes (Kelly and Callegari 4978). At this point, it should be noted that the process of DNA replication is a crucial similarity between eukaryotic and prokaryotic cells. Although the two cell types are distinctively different from each other, the replication of DNA occurs in both cell types according to the same scheme and set of principles.

However, there are some differences in the replication process that allow distinguishing between a prokaryotic and eukaryotic cell based on the DNA replication characteristics. For example, unlike eukaryotic cells, prokaryotic ones have only one point of origin of their replication, which, in turn, occurs only in two directions (Kelly and Callegari 4978). In addition, the entire replication process occurs at a much faster pace than the one in eukaryotic cells and takes approximately 40 minutes (compared to several hours in a complex eukaryotic cell) (Kelly and Callegari 4977).

The described characteristic allows prokaryotic cells to undergo the replication process in an endless cycle, which is impossible in eukaryotic cells due to the presence of telomeres in their chromosomes (“Chapter 4 – Cell Structure”). Thus, the DNA replication process can be regarded as one of the crucial differences between eukaryotic and prokaryotic cells.

The presence of mitochondria in eukaryotic cells as their distinctive feature is the subject of particular interest since the current theories of mitochondria origin allow tracking down the evolution of a prokaryotic cell to a eukaryotic one. According to the theory of endosymbiotic hypothesis, mitochondria were initially prokaryotic cells (). Moreover, like cells, mitochondria could perform the functions of which eukaryotic cells were incapable (“Chapter 4 – Cell Structure”).

However, since the oxidative processes that mitochondria performed were also essential for the proper functioning of eukaryotic cells, the latter acquired mitochondria via endosymbiosis (). As a result, mitochondria are a crucial component of eukaryotic cells nowadays, yet they are completely absent from prokaryotic ones. Providing opportunities for energy conversion, mitochondria in eukaryotes primarily serve to produce ATP, although it also has several other important functions.

Comparing eukaryotic and prokaryotic cells is necessary since it provides insightful results that may prompt a more nuanced understanding of the functioning of cells and tissues, as well as the factors that lead to the disruption in the processes of them. Thus, an improved approach toward treating patients will become possible. While the key distinction between eukaryotic and prokaryotic cells is the nucleus, which is absent in the latter, there are also numerous nuances that allow differentiating between the two cell types.

“Chapter 4 – Cell Structure.” Georgia Highlands College , n.d. Web.

Kelly, Thomas, and A. John Callegari. “Dynamics of DNA Replication in a Eukaryotic Cell.” Proceedings of the National Academy of Sciences , vol. 116, no. 11, 2019, pp. 4973-4982.

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• Biology Article
• Prokaryotic And Eukaryotic Cells

Difference between Prokaryotic and Eukaryotic Cells

Introduction: prokaryotes and eukaryotes.

Biotic components of the environment include all forms of life from minute bacteria to towering giant Sequoias. However, at the microscopic level, all living organisms are made up of the same basic unit – the cell.

Prokaryotic Cell

Eukaryotic cell.

As a result, the cell is referred to as the structural and functional unit of all living organisms.  The word cell has its origins in Latin, and when translated, it means “small room” and was first observed by Robert Hooke – an English natural philosopher in the year 1665.

He also compared his discovery to the cells in a honeycomb, as they showcase a similar structure.

An image illustrating the difference between Prokaryotic and Eukaryotic Cells. Note that the prokaryotic cell is a complete individual organism

Eventual advancements in science and technology shed more light into the cell, with new findings and discoveries about its structure and cellular components.  During the 1950s, scientists postulated the concept of prokaryotic cells and eukaryotic cells, with earlier groundwork being laid by Edouard Chatton, a French Biologist in 1925.

Anatomically, cells vary with respect to their classification, therefore, prokaryotic cells and eukaryotic cells differ from each other quite drastically. Read on to explore how they differ from each other.

The term “ prokaryote ” is derived from the Greek word “ pro “, (meaning: before) and “ karyon ” (meaning: kernel). It translates to “ before nuclei. “

Prokaryotes are one of the most ancient groups of living organisms on earth, with fossil records dating back to almost 3.5 billion years ago.

These prokaryotes  thrived in the earth’s ancient environment, some using up chemical energy and others using the sun’s energy. These extremophiles thrived for millions of years, evolving and adapting. Scientists speculate that these organisms gave rise to the eukaryotes.

Prokaryotic cells are comparatively smaller and much simpler than eukaryotic cells. The other defining characteristic of prokaryotic cells is that it does not possess membrane-bound cell organelles such as a nucleus. Reproduction happens  through the process of binary fission.

Structurally, prokaryotes have a capsule enveloping their entire body, and it functions as a protective coat. This is crucial for preventing the process of phagocytosis (where the bacteria gets engulfed by other eukaryotic cells, such as macrophages) The pilus is a hair-like appendage found on the external surface of most prokaryotes and it helps the organism to attach itself to various environments. The pilus essentially resists being flushed, hence, it is also called attachment pili. It is commonly observed in bacteria.

Right below the protective coating lies the cell wall, which provides strength and rigidity to the cell. Further down lies the cytoplasm that helps in cellular growth, and this is contained within the plasma membrane, which separates the interior contents of the cell from the outside environment.  Within the cytoplasm, ribosomes exist and it plays an important role in protein synthesis. It is also one of the smallest components within the cell. 

Some prokaryotic cells contain special structures called mesosomes which assist in cellular respiration . Most prokaryotes also contain plasmids, which contain small, circular pieces of DNA. To help with locomotion,  flagella are present, though, pilus can also serve as an aid for locomotion.  Common examples of Prokaryotic organisms are bacteria and archaea. Also, all members of Kingdom Monera are prokaryotes.

Main Article:   Prokaryotic Cells

The term “ Eukaryotes ” is derived from the Greek word “ eu “, (meaning: good) and “ karyon ” (meaning: kernel), therefore, translating to “ good or true nuclei .” Eukaryotes are more complex and much larger than prokaryotes.   They include almost all the major kingdoms except kingdom monera.

Structurally, eukaryotes possess a cell wall, which supports and protects the plasma membrane. The cell is surrounded by the plasma membrane and it controls the entry and exit of certain substances.

The nucleus contains DNA, which is responsible for storing all genetic information. The nucleus is surrounded by the nuclear membrane. Within the nucleus exists the nucleolus, and it plays a crucial role in synthesising proteins. Eukaryotic cells also contain mitochondria, which are responsible for the creation of energy, which is then utilized by the cell.

Present in only plant cells, chloroplasts are the subcellular sites of photosynthesis. The endoplasmic reticulum helps in the transportation of materials. Besides these, there are also other cell organelles that perform various other functions and these include  ribosomes, lysosomes, Golgi bodies, cytoplasm, chromosomes, vacuoles and centrosomes.

Examples of eukaryotes include almost every unicellular organism with a nucleus and all multicellular organisms.

Main Article:  Eukaryotic Cells

Though these two classes of cells are quite different, they do possess some common characteristics. For instance, both possess cell membranes and ribosomes, but the similarities end there. The complete list of differences between prokaryotic and eukaryotic cells is summarized as follows:

Learn more about prokaryotic cell and eukaryotic cell, their differences and other related topics at BYJU’S Biology

Frequently Asked Questions

What is a prokaryotic cell.

A prokaryotic cell is a primitive type of cell that is characterized by the absence of a nucleus. Furthermore, prokaryotes do not possess membrane-bound cellular organelles. Prokaryotes are exclusively unicellular.

What is a Eukaryotic cell?

Eukaryotic cells are cells that possess a true nucleus along with membrane-bound organelles. Eukaryotes can either be unicellular or multicellular.

What is the difference between Prokaryotic and Eukaryotic cells?

The defining characteristic feature that distinguishes between prokaryotic and eukaryotic cell is the nucleus. In prokaryotic cells, the true nucleus is absent, moreover, membrane-bound organelles are present only in eukaryotic cells. Another major difference between prokaryotic and eukaryotic cells is that prokaryotic cells are exclusively unicellular, while the same does not apply to eukaryotic cells.

Define Cell?

The cell is the basic functional and structural unit of life. Cell plays a vital role in all biological activities and include membrane-bound organelles, which perform several individual functions to keep the cell alive and active.

What is Ribosome?

The ribosome is a multi-component cell organelle consisting of RNA and protein. Therefore, it is called the site of protein synthesis. Ribosomes are present both in prokaryotic and eukaryotic cells. Compared to prokaryotes, eukaryotes have larger ribosomes in their cells.

List out the unique features of Animal and Plant Cells.

Both animal and plant cells have several unique features. Listed below are some important features:

• In structure, both animal and plant cells are quite similar.
• Both possess nucleus and plasma membrane, a selectively permeable membrane of the cell.
• Both animal and plant cells include membrane-bound organelles with their specialized functions.
• Animal and plant cells have vacuoles, which serve as the storage unit and maintain the shape of the cell.
• Mitochondria is the powerhouse of the cell. It stores and provide energy for different cellular activities and is found both in both animal and plant cells.

List out the functions of Chloroplasts.

Chloroplasts are the plastids found in all plant cells. These cell organelles comprise the photosynthetic pigment called chlorophyll and are involved in synthesizing food by the process of photosynthesis.

Who discovered Cell and Cell Theory?

The cell was first discovered in the year 1665 by an English natural philosopher Robert Hooke. The Cell Theory was explained by Theodor Schwann and Matthias Jakob Schleiden in the year 1830.

Further Reading:

• Competent Cells
• Difference Between Plasmid DNA And Chromosomal DNA

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3.2 Comparing Prokaryotic and Eukaryotic Cells

Learning objectives.

• Name examples of prokaryotic and eukaryotic organisms
• Compare and contrast prokaryotic cells and eukaryotic cells
• Describe the relative sizes of different kinds of cells

Cells fall into one of two broad categories: prokaryotic and eukaryotic. The predominantly single-celled organisms of the domains Bacteria and Archaea are classified as prokaryotes ( pro - = before; - karyon - = nucleus). Animal cells, plant cells, fungi, and protists are eukaryotes ( eu - = true).

Components of Prokaryotic Cells

All cells share four common components: 1) a plasma membrane, an outer covering that separates the cell’s interior from its surrounding environment; 2) cytoplasm, consisting of a jelly-like region within the cell in which other cellular components are found; 3) DNA, the genetic material of the cell; and 4) ribosomes, particles that synthesize proteins. However, prokaryotes differ from eukaryotic cells in several ways.

A prokaryotic cell is a simple, single-celled (unicellular) organism that lacks a nucleus, or any other membrane-bound organelle. We will shortly come to see that this is significantly different in eukaryotes. Prokaryotic DNA is found in the central part of the cell: a darkened region called the nucleoid ( Figure 3.5 ).

Unlike Archaea and eukaryotes, bacteria have a cell wall made of peptidoglycan, comprised of sugars and amino acids, and many have a polysaccharide capsule ( Figure 3.5 ). The cell wall acts as an extra layer of protection, helps the cell maintain its shape, and prevents dehydration. The capsule enables the cell to attach to surfaces in its environment. Some prokaryotes have flagella, pili, or fimbriae. Flagella are used for locomotion, while most pili are used to exchange genetic material during a type of reproduction called conjugation.

Eukaryotic Cells

In nature, the relationship between form and function is apparent at all levels, including the level of the cell, and this will become clear as we explore eukaryotic cells. The principle “form follows function” is found in many contexts. For example, birds and fish have streamlined bodies that allow them to move quickly through the medium in which they live, be it air or water. It means that, in general, one can deduce the function of a structure by looking at its form, because the two are matched.

A eukaryotic cell is a cell that has a membrane-bound nucleus and other membrane-bound compartments or sacs, called organelles , which have specialized functions. The word eukaryotic means “true kernel” or “true nucleus,” alluding to the presence of the membrane-bound nucleus in these cells. The word “organelle” means “little organ,” and, as already mentioned, organelles have specialized cellular functions, just as the organs of your body have specialized functions.

At 0.1–5.0 µm in diameter, prokaryotic cells are significantly smaller than eukaryotic cells, which have diameters ranging from 10–100 µm ( Figure 3.6 ). The small size of prokaryotes allows ions and organic molecules that enter them to quickly spread to other parts of the cell. Similarly, any wastes produced within a prokaryotic cell can quickly move out. However, larger eukaryotic cells have evolved different structural adaptations to enhance cellular transport. Indeed, the large size of these cells would not be possible without these adaptations. In general, cell size is limited because volume increases much more quickly than does cell surface area. As a cell becomes larger, it becomes more and more difficult for the cell to acquire sufficient materials to support the processes inside the cell, because the relative size of the surface area across which materials must be transported declines.

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Prokaryotic vs. Eukaryotic Cells: What's the Difference?

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You know when you hear somebody start a sentence with, "There are two kinds of people..." and you think to yourself "Oh boy, here it comes."

But what if I were to tell you that there are just two kinds of organisms?

According to scientists, the world is split into two kinds of organisms — prokaryotic vs. eukaryotic — which have two different types of cells . An organism can be made up of either one type or the other. Some organisms consist of only one measly cell, but even so, that cell will either be either prokaryotic or eukaryotic. It's just the way things are.

Organelles in Complex Eukaryotic Cells

Prokaryotic efficiency apartment vs. eukaryotic mansion, the evolution of eukaryotes.

The difference between eukaryotic and prokaryotic cells has to do with the little stuff-doing parts of the cell, called organelles.

Prokaryotic cells are simpler and lack the eukaryote's membrane-bound organelles and nucleus, which encapsulate the cell's DNA . Though more primitive than eukaryotes, prokaryotic bacteria are the most diverse and abundant group of organisms on Earth . We humans are literally covered in prokaryotes, inside and out.

On the other hand, all humans, animals, plants, fungi and protists are made up of eukaryotic cells. And though some eukaryotes are single-celled — think amoebas and paramecium — there are no prokaryotes that have more than one cell.

"I think of a prokaryote as a one-room efficiency apartment and a eukaryote as a $6 million mansion," says Erin Shanle, a professor in the Department of Biological and Environmental Sciences at Longwood University, in an email interview. "The size and separation of functional 'rooms,' or organelles, in eukaryotes is similar to the many rooms and complex organization of a mansion. Prokaryotes have to get similar jobs done in a single room without the luxury of organelles."

One reason this analogy is helpful is because all cells, both prokaryotes and eukaryotes, are surrounded by a selectively permeable membrane which allows only certain molecules to get in and out — much like the windows and doors of our home.

You can lock your doors and windows to keep out stray cats and burglars (the cellular equivalent to viruses or foreign materials), but you unlock the doors to bring in groceries and to take out the trash. In this way, all cells maintain internal homeostasis , or stability.

"Prokaryotes are much simpler with respect to structure," says Shanle. "They have a single 'room' to perform all the necessary functions of life, namely producing proteins from the instructions stored in DNA, which is the complete set of instructions for building a cell. Prokaryotes don't have separate compartments for energy production, protein packaging, waste processing or other key functions."

In contrast, eukaryotic cells have membrane-bound organelles that are used to separate all these processes, which means the kitchen is separate from the master bathroom — there are dozens of walled-off rooms, all of which serve a different function in the cell.

For example, DNA is stored, replicated and processed in the eukaryotic cell's nucleus, which is itself surrounded by a selectively permeable membrane. This protects the DNA and allows the cell to fine-tune the production of proteins necessary to do its job and keep the cell alive.

Other key organelles include:

• Mitochondria : Processes sugars to generate energy
• Lysosome : Processes waste
• Endoplasmic reticulum : Helps organize proteins for distribution around the cell.

Prokaryotic cells have to do a lot of this same stuff, but they just don't have separate rooms to do it in. They're more of a two-bit operation in this sense.

"Many eukaryotic organisms are made up of multiple cell types, each containing the same set of DNA blueprints, but which perform different functions," says Shanle. "By separating the large DNA blueprints in the nucleus, certain parts of the blueprint can be utilized to create different cell types from the same set of instructions."

You might be wondering how organisms got to be divided in this way. Well, according to endosymbiotic theory, it all started about 2 billion years ago, when some large prokaryote managed to create a nucleus by folding its cell membrane in on itself.

"Over time, a smaller prokaryotic cell was engulfed by this larger cell," says Shanle. "The smaller prokaryote could perform aerobic respiration, or process sugars into energy using oxygen, similar to the mitochondria we see in eukaryotes that are living today. This smaller cell was maintained within the larger host cell, where it replicated and was passed on to subsequent generations. This endosymbiotic relationship ultimately led to the smaller cell becoming a part of the larger cell, eventually losing its autonomy and much of its original DNA."

However, the mitochondria of today's eukaryotes have their own DNA blueprints that replicate independently from the DNA in the nucleus, and mitochondrial DNA has some similarity to prokaryotic DNA, which supports the endosymbiotic theory.

A similar model is thought to have led to the evolution of chloroplasts in plants, but the story begins with a eukaryotic cell containing a mitochondria engulfing a photosynthetic prokaryote.

Eukaryotes and prokaryotes — they're different! But even though it can be hard to see the similarities between humans and bacteria, we are all made of the same stuff: DNA, proteins, sugars and lipids.

Although endosymbiotic theory is just "a theory," it's the best explanation of the evolution of eukaryotes. Though it may one day be disproven, it's supported by lots of facts.

Prokaryotic Cell FAQ

What is a prokaryotic cell, what is the structure of a prokaryotic cell, what is the difference between a prokaryotic and eukaryotic cell, what is an example of a prokaryotic cell, what is the main function of a prokaryotic cell.

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Eukaryotic Cell vs. Prokaryotic Cell

The distinction between prokaryotes and eukaryotes is considered to be the most important distinction among groups of organisms. Eukaryotic cells contain membrane-bound organelles, such as the nucleus, while prokaryotic cells do not. Differences in cellular structure of prokaryotes and eukaryotes include the presence of mitochondria and chloroplasts, the cell wall, and the structure of chromosomal DNA .

Prokaryotes were the only form of life on Earth for millions of years until more complicated eukaryotic cells came into being through the process of evolution.

Comparison chart

Definition of eukaryotes and prokaryotes.

Prokaryotes (pro-KAR-ee-ot-es) (from Old Greek pro- before + karyon nut or kernel, referring to the cell nucleus, + suffix -otos , pl. -otes ; also spelled "procaryotes") are organisms without a cell nucleus (= karyon), or any other membrane-bound organelles. Most are unicellular, but some prokaryotes are multicellular.

Eukaryotes (IPA: [juːˈkæɹɪɒt]) are organisms whose cells are organized into complex structures by internal membranes and a cytoskeleton. The most characteristic membrane bound structure is the nucleus. This feature gives them their name, (also spelled "eucaryote,") which comes from the Greek ευ, meaning good/true, and κάρυον, meaning nut, referring to the nucleus. Animals , plants, fungi, and protists are eukaryotes.

Differences Between Eukaryotic and Prokaryotic Cells

The difference between the structure of prokaryotes and eukaryotes is so great that it is considered to be the most important distinction among groups of organisms.

• The most fundamental difference is that eukaryotes do have "true" nuclei containing their DNA, whereas the genetic material in prokaryotes is not membrane-bound.

• In eukaryotes, the mitochondria and chloroplasts perform various metabolic processes and are believed to have been derived from endosymbiotic bacteria . In prokaryotes similar processes occur across the cell membrane; endosymbionts are extremely rare.
• The cell walls of prokaryotes are generally formed of a different molecule (peptidoglycan) to those of eukaryotes (many eukaryotes do not have a cell wall at all).
• Prokaryotes are usually much smaller than eukaryotic cells.
• Prokaryotes also differ from eukaryotes in that they contain only a single loop of stable chromosomal DNA stored in an area named the nucleoid, while eukaryote DNA is found on tightly bound and organised chromosomes. Although some eukaryotes have satellite DNA structures called plasmids, these are generally regarded as a prokaryote feature and many important genes in prokaryotes are stored on plasmids.
• Prokaryotes have a larger surface area to volume ratio giving them a higher metabolic rate, a higher growth rate and consequently a shorter generation time compared to Eukaryotes.

• Prokaryotes also differ from eukaryotes in the structure, packing, density, and arrangement of their genes on the chromosome. Prokaryotes have incredibly compact genomes compared to eukaryotes, mostly because prokaryote genes lack introns and large non-coding regions between each gene.
• Whereas nearly 95% of the human genome does not code for proteins or RNA or includes a gene promoter, nearly all of the prokaryote genome codes or controls something.
• Prokaryote genes are also expressed in groups, known as operons, instead of individually, as in eukaryotes.
• In a prokaryote cell, all genes in an operon(three in the case of the famous lac operon) are transcribed on the same piece of RNA and then made into separate proteins, whereas if these genes were native to eukaryotes, they each would have their own promoter and be transcribed on their own strand of mRNA. This lesser degree of control over gene expression contributes to the simplicity of the prokaryotes as compared to the eukaryotes.

• Wikipedia:Eukaryote
• Wikipedia:Prokaryote

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4.6: Comparing Prokaryotic and Eukaryotic Cells

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Cells fall into one of two broad categories: prokaryotic and eukaryotic. The single-celled organisms of the domains Bacteria and Archaea are classified as prokaryotes ( pro = before; karyon – = nucleus). Animal cells, plant cells, fungi, and protists are eukaryotes ( eu = true).

Components of Prokaryotic Cells

All cells share four common components: (1) a plasma membrane, an outer covering that separates the cell’s interior from its surrounding environment; (2) cytoplasm, consisting of a jelly-like region within the cell in which other cellular components are found; (3) DNA, the genetic material of the cell; and (4) ribosomes, particles that synthesize proteins. However, prokaryotes differ from eukaryotic cells in several ways.

A prokaryotic cell is a simple, single-celled (unicellular) organism that lacks a nucleus, or any other membrane-bound organelle. We will shortly come to see that this is significantly different in eukaryotes. Prokaryotic DNA is found in the central part of the cell: a darkened region called the nucleoid (Figure 1).

Unlike Archaea and eukaryotes, bacteria have a cell wall made of peptidoglycan, comprised of sugars and amino acids, and many have a polysaccharide capsule (Figure 1). The cell wall acts as an extra layer of protection, helps the cell maintain its shape, and prevents dehydration. The capsule enables the cell to attach to surfaces in its environment. Some prokaryotes have flagella, pili, or fimbriae. Flagella are used for locomotion, while most pili are used to exchange genetic material during a type of reproduction called conjugation.

Eukaryotic Cells

In nature, the relationship between form and function is apparent at all levels, including the level of the cell, and this will become clear as we explore eukaryotic cells. The principle “form follows function” is found in many contexts. It means that, in general, one can deduce the function of a structure by looking at its form, because the two are matched. For example, birds and fish have streamlined bodies that allow them to move quickly through the medium in which they live, be it air or water.

A eukaryotic cell is a cell that has a membrane-bound nucleus and other membrane-bound compartments or sacs, called organelles , which have specialized functions. The word eukaryotic means “true kernel” or “true nucleus,” alluding to the presence of the membrane-bound nucleus in these cells. The word “organelle” means “little organ,” and, as we learned earlier, organelles have specialized cellular functions, just as the organs of your body have specialized functions.

At 0.1–5.0 µm in diameter, prokaryotic cells are significantly smaller than eukaryotic cells, which have diameters ranging from 10–100 µm (Figure 2). The small size of prokaryotes allows ions and organic molecules that enter them to quickly spread to other parts of the cell. Similarly, any wastes produced within a prokaryotic cell can quickly move out. However, larger eukaryotic cells have evolved different structural adaptations to enhance cellular transport. Indeed, the large size of these cells would not be possible without these adaptations. In general, cell size is limited because volume increases much more quickly than does cell surface area. As a cell becomes larger, it becomes more and more difficult for the cell to acquire sufficient materials to support the processes inside the cell, because the relative size of the surface area across which materials must be transported declines.

Learning Objectives

Prokaryotes are single-celled organisms of the domains Bacteria and Archaea. All prokaryotes have plasma membranes, cytoplasm, ribosomes, a cell wall, DNA, and lack membrane-bound organelles. Many also have polysaccharide capsules. Prokaryotic cells range in diameter from 0.1–5.0 µm.

Like a prokaryotic cell, a eukaryotic cell has a plasma membrane, cytoplasm, and ribosomes, but a eukaryotic cell is typically larger than a prokaryotic cell, has a true nucleus (meaning its DNA is surrounded by a membrane), and has other membrane-bound organelles that allow for compartmentalization of functions. Eukaryotic cells tend to be 10 to 100 times the size of prokaryotic cells.

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What is the difference between prokaryotic and eukaryotic cells?

Discover the structural and functional difference between prokaryotic and eukaryotic cells

• Common features
• Major differences

Additional resources

Bibliography.

The main difference between prokaryotic and eukaryotic cells lies in their structure.

Prokaryotic cells and eukaryotic cells are the two types of cells that exist on Earth . There are several differences between the two, but the biggest distinction between them is that eukaryotic cells have a distinct nucleus containing the cell's genetic material, while prokaryotic cells don't have a nucleus and have free-floating genetic material instead. 

What are prokaryotic and eukaryotic cells?

All living things can be divided into three basic domains: Bacteria , Archaea and Eukarya. The primarily single-celled organisms found in the Bacteria and Archaea domains are known as prokaryotes. These organisms are made of prokaryotic cells — the smallest, simplest and most ancient cells.

Organisms in the Eukarya domain are made of the more complex eukaryotic cells. These organisms, called eukaryotes, can be unicellular or multicellular and include animals, plants, fungi and protists . Many people are unclear on whether yeasts or fungi are prokaryotes or eukaryotes. Both are eukaryotes and share similar cell structure to all other eukaryotes.

There is evidence to suggest that eukaryotes are the descendants of separate prokaryotic cells, according to Berkeley University of California.  

Eukaryotes developed at least 2.7 billion years ago, following 1 to 1.5 billion years of prokaryotic evolution , according to the National Institutes of Health (NIH) . Scientists hypothesize that the nucleus and other eukaryotic features may have first formed after a prokaryotic organism swallowed up another, according to the University of Texas . 

It’s also been suggested that tiny organelles in eukaryotic cells – called mitochondria – may also be the descends of prokaryotic living-bacterium which were engulfed by other cells and remained in the cell as a permanent guest, according to Berkeley University. 

What do prokaryotes and eukaryotes have in common?

Although prokaryotic and eukaryotic cells have many differences, they share some common features, including the following:

• DNA : Genetic coding that determines all the characteristics of living things.
• Cell (or plasma) membrane: Outer layer that separates the cell from the surrounding environment and acts as a selective barrier for incoming and outgoing materials.
• Cytoplasm: Jelly-like fluid within a cell that is composed primarily of water, salts and proteins.
• Ribosomes: Organelles that make proteins.

How do prokaryotes and eukaryotes differ?

Eukaryotic cells have a nucleus surrounded by a nuclear envelope that consists of two lipid membranes, according to Nature E d ucation . The nucleus holds the eukaryotic cell's DNA. Prokaryotic cells do not have a nucleus; rather, they have a membraneless nucleoid region (open part of the cell) that holds free-floating DNA, according to Washington University .

The entire DNA in a cell can be found in individual pieces known as chromosomes . Eukaryotic cells have many chromosomes which undergo meiosis and mitosis during cell division, while most prokaryotic cells consist of just one circular chromosome. However, recent studies have shown that some prokaryotes have as many as four linear or circular chromosomes, according to Nature Education . For example, Vibrio cholerae, the bacterium that causes cholera , has two circular chromosomes.

Eukaryotic cells have several other membrane-bound organelles not found in prokaryotic cells. These include the mitochondria (convert food energy into adenosine triphosphate, or ATP, to power biochemical reactions); rough and smooth endoplasmic reticulum (an interconnected network of membrane-enclosed tubules that transport synthesized proteins); golgi complex (sorts and packages proteins for secretion); and in the case of plant cells, chloroplasts (conduct photosynthesis ). All of these organelles are located in the eukaryotic cell's cytoplasm.

Although only eukaryotes carry membrane-bound organelles, recent evidence suggests that both eukaryotes and prokaryotes can produce organelle-like structures that lack membranes, according to a 2020 report published in the journal Proceedings of the National Academy of Sciences (PNAS).

For instance, in the bacterium Escherichia coli , molecules and proteins cluster together to form liquid "compartments" within the cytoplasm, according to the PNAS study. These compartments form similarly to how oil forms droplets when mixed with water, according to a statement from the University of Michigan . Such membraneless structures have been reported in many bacterial species, including Mycobacterium tuberculosis , which causes tuberculosis, and cyanobacteria, a type of photosynthetic bacteria that can also cause disease.

In eukaryotic cells, the ribosomes are bigger, more complex and bound by a membrane. They can be found in various places: Sometimes in the cytoplasm; on the endoplasmic reticulum; or attached to the nuclear membrane (covering on the nucleus).

In prokaryotic cells, the ribosomes are scattered and floating freely throughout the cytoplasm. The ribosomes in prokaryotic cells also have smaller subunits. All ribosomes (in both eukaryotic and prokaryotic cells) are made of two subunits — one larger and one smaller. In eukaryotes, these pieces are identified by scientists as the 60-S and 40-S subunits. In prokaryotes, the ribosomes are made of slightly smaller subunits, called 50-S and 30-S.

– Robert Hooke: English scientist who discovered the cell

– The Human Body: Anatomy, facts & functions

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The difference in types of subunits has allowed scientists to develop antibiotic drugs , such as streptomycin, that attack certain types of infectious bacteria, according to the British Society for Cell Biology . On the downside, some bacterial toxins and the polio virus use the ribosome differences to their advantage; they're able to identify and attack eukaryotic cells' translation mechanism, or the process by which messenger RNA is translated into proteins.

Most eukaryotes also reproduce sexually (although some protists and single-celled fungi may reproduce through mitosis, which is functionally similar to asexual reproduction). Prokaryotes reproduce asexually, resulting in the offspring being an exact clone of the parent. Some prokaryotic cells also have pili, which are adhesive hair-like projections used to exchange genetic material during a type of sexual process called conjugation, according to Concepts of Biology . Conjugation can occur in bacteria, protozoans and some algae and fungi.

Most prokaryotic cells have a rigid cell wall that surrounds the plasma membrane and gives shape to the organism. In eukaryotes, vertebrates don't have a cell wall but plants do. The cell walls of prokaryotes differ chemically from the eukaryotic cell walls of plant cells, which are primarily made of cellulose. In bacteria, for example, the cell walls are composed of peptidoglycans (sugars and amino acids), according to Washington University .

Check out this animated video by the Amoeba Sisters that explains the difference between prokaryotic and eukaryotic cells. To take a more indepth look into all the cells in the world take a look at Looking Inside Cells: Life Science by Kimerberly Fekany Lee. 

Lesli J Favor, “ How Eukaryotic and Prokaryotic Cells Differ (Britannica Guide to Cell Biology) ,” Rosen Publishing, 2014.

Frantisek Baluska et al, “Eukaryotic Cells and their Cell Bodies: Cell Theory Revised”, Annals of Botany, Volume 94, Jukly 2004, https://doi.org/10.1093/aob/mch109  

James Wagstaff & Jan Lowe, “Prokaryotic cytoskeletons: protein filaments organizing small cells”, Nature Reviews Microbiology, Volume 16, January 2018, https://doi.org/10.1038/nrmicro.2017.153  

Avadhesha Surolia & Abhijit Chakrabarti, “ Biochemical Roles of Eukaryotic Cell Surface Macromolecules ”, Springer International Publishing, 2014.

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Prokaryotes vs. Eukaryotes

All living organisms can be grouped into two types based on their fundamental cell structure. They are prokaryotes and eukaryotes, and the cells they possess are called prokaryotic cells and eukaryotic cells.

Prokaryotes are primitive organisms lacking a nucleus and membrane-bound organelles. The term ‘prokaryote’ is derived from the Greek words ‘pro’, meaning ‘before’ and ‘karyon’, meaning ‘kernel’. Together it means ‘before nuclei’. In contrast, eukaryotes are advanced organisms with a well-defined nucleus and membrane-bound organelles. The term ‘eukaryotes’ is derived from the Greek words ‘eu’, meaning ‘good’ and ‘karyon’, meaning ‘kernel’, meaning ‘true nuclei’. The eukaryotes are thought to have originated from the prokaryotes about 2.7 billion years ago.

Compare and Contrast Prokaryotic and Eukaryotic Cells

Although they share some common characteristics, prokaryotic and eukaryotic cells differ in most aspects, such as cell size, shape, organization, and life cycle, including reproduction. The main differences are given below.

What is the Difference between Prokaryotic and Eukaryotic Cells

What do prokaryotes and eukaryotes have in common.

Both prokaryotic and eukaryotic cells are alike in some ways and share some common features that are given below:

• Plasma Membrane , an outer covering that allows selective entry and exit of substances in and out of the cell, is found in both cell types. Their fundamental composition in forming a lipid bilayer with embedded proteins is also the same.
• Both contain  cytoplasm , a jelly-like fluid that fills the cell’s entire interior, where all other cellular components are found.
• DNA  is the genetic material in both cell types.
• In both,  ribosomes  help in protein synthesis.

Ans . Viruses are not cells and thus are neither a prokaryote nor a eukaryote.

Ans .  Amoeba,  being a protist, are eukaryotes.

Ans . Yeast, being fungi, is a eukaryote.

Ans . Eubacteria, or ‘true’ bacteria, are a class of bacteria and thus are prokaryotes.

Ans .  E .  coli, being bacteria, is a prokaryote.

Ans . Human cells have a true nucleus and membrane-bound organelles and thus are eukaryotes.

Ans .  Euglena,  being protist, are eukaryotes.

Ans . Cyanobacteria or blue-green algae lack membrane-bound organelles and well-organized nuclei and thus are prokaryotes.

Ans . Yes. Eukaryotes originated at least 2.7 billion years ago, following almost 1 to 1.5 billion years of prokaryotic evolution.

Ans . Prokaryotic protein synthesis uses 70S ribosomes in comparison to 80S ribosomes in eukaryotes. Protein synthesis in prokaryotes is a continuous process with transcription. On the other hand, in eukaryotes, protein synthesis starts after transcription is complete.

Ans .  Elodea  is a plant genus, and thus is a eukaryote.

Ans . Onion cells and cheek cells are eukaryotic cells because they possess membrane-bound organelles and a well-organized nucleus.

Ans . Mold, being fungi, is a eukaryote.

Ans . HIV, being a virus , is neither a prokaryote nor a eukaryote.

Ans .  Streptococcus  is a bacterial genus and thus is a prokaryote.

Ans . As cancer cells are found only in multicellular organisms, which are eukaryotes, they are eukaryotic cells.

Ans . All red blood cells , including rodent red blood cells, are eukaryotic because they have a true nucleus and membrane-bound organelles.

Ans . Fish cells, including sharks, are eukaryotic because they have a true nucleus and membrane-bound organelles.

Ans . Monera is a kingdom that includes bacteria and archaea. They have a prokaryotic cell organization.

Ans.  Saccharomyces  is a genus of fungi, including many yeast species. They are thus eukaryotes.

Ans.  Spirillum is  a bacterial genus and thus is a prokaryote.

Ans.  Vibrio cholera,  being bacteria, is a prokaryote.

• Prokaryotes Vs. Eukaryotes: What Are the Differences? – Thoughtco.com
• 47 Differences between Prokaryotes and Eukaryotes – Microbenotes.com
• Prokaryotic versus Eukaryotic Cells – Ib.bioninja.com.au
• Prokaryotic vs. Eukaryotic Cells: What’s the Difference?  – Livescience.com

Article was last reviewed on Monday, October 9, 2023

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An Essay on the Differences between Prokaryote & Eukaryote cells.

An Essay on the Differences between

 Prokaryote & Eukaryote cells

All cellular organism fall into two natural groups, known as prokaryotes and eukaryotes. These two groups are fundamentally different. The terms prokaryote  and eukaryote refer to the differences in the location of the DNA. In prokaryotes the DNA is not enclosed by nuclear membranes and lies free in the cytoplasm. The cells therefore lack true nuclei . The cells of eukaryotes , however, do contain true nuclei.

Eukaryotes arose around 1.2 thousand million years ago, and they evolved from prokaryotes which began around 3.5 thousand million years ago.

Although the location of the DNA in the cells is the major difference between the cell types, there are many more differences, which are explored below.

The sizes of the cells are vastly different, in prokaryotes the average diameter of the cell is 0.5-10μm. However, eukaryote cells are much larger in comparison, they are typically 1000-10000 times the volume of prokaryote cells, and their common diameter is 10-100μm.

Prokaryotes mainly arise in unicellular forms and examples of organisms that are prokaryotic is bacteria. Eukaryotes on the other hand arise in multicellular form and examples of eukaryotic celled organisms are fungi, plants, animals and the exception which are protoctist as many of them are unicellular.

This is a preview of the whole essay

As mentioned above the DNA lies free in the cytoplasm of prokaryotes, and lies linear and in a nucleus in eukaryotes. However, in prokaryotes the DNA is ‘naked’ and therefore is not associated with proteins or RNA to form chromosomes. While in eukaryotes the DNA is not naked and is associated with protein & RNA to form chromosomes.

In the two types of cells the ribosomes which are used in protein synthesis are slightly different, in prokaryotic cells the ribosome are 70S and smaller than the 80S larger ribosomes in eukaryotic cells.

In eukaryotic cells the ribosomes may be attached to the endoplasmic reticulum, while in prokaryotic cells there is no endoplasmic reticulum.

When it comes to organelles prokaryotes have relatively few, and the ones present have no envelope surrounding them. Furthermore, prokaryotes have few internal membranes, and if present they are usually only used for respiration or photosynthesis.

On the other hand eukaryotes have many organelles, and many are envelope bounded such as the nucleus or mitochondria. In addition, eukaryotes have a great number and diversity of organelles bounded by single membranes for example Golgi apparatus or lysosomes.

When it comes to respiration, prokaryotes like bacteria use mesosomes, the exceptions being cytoplasmic membranes in blue-green bacteria. While eukaryotes use the organelle- mitochondria, which combines glucose and oxygen in the process of aerobic respiration to give energy.

Eukaryotes in addition have the capabilities to photosynthesize due to organelles such as chloroplast in its cells. While prokaryotes also can photosynthesize but have no chloroplast they create food from membranes which show no stacking in it cells.

Nitrogen fixation is the ability to change the form of nitrogen. Eukaryotic cells do not have the ability to carry out nitrogen fixation, while on the other hand prokaryotic cells do.

The structures of the cell walls and compositions of them are greatly different in the cells. In eukaryotes the cell walls of green plants and fungi are rigid and contain polysaccharides; cellulose is the main strengthening compound in plant walls and chitin in fungal walls, however, there are none in animal cells.

However, prokaryotes cell walls are rigid and contain polysaccharides with amino acids, and murein is the main strengthening compound.

Finally when it comes to movement of the cells, flagellum is used in cells; however the flagellum in prokaryotes and eukaryotes are slightly different. In prokaryote cells the flagella is simple and lacking in microtubules, it is also extra cellular, and it has an average diameter of 20nm.

On the other hand in eukaryotes the structure is complex with ‘9+2’ arrangement of microtubules, it is also intracellular, and the eukaryote flagella also have a diameter of around 200nm.

In conclusion, as seen there are many differences between prokaryotes and eukaryotes, in functions, structure and processes.

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