Similarities & Differences between Prokaryotic and Eukaryotic Cells

A biological comparison of the 2 types of cells' structure, size, reproduction, and more

Co-authored by Dan Hickey

Last Updated: February 28, 2023 References

Cell Similarities

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Prokaryote-Specific Traits

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Eukaryote-Specific Traits

Cells are complicated little things that come in all sorts of shapes and sizes and perform a lot of very different functions. Despite their incredible diversity, there are a handful of things that all cells have in common whether they’re a single-celled bacteria or a red blood cell inside of a chihuahua. In this article, we’ll walk you through the similarities between prokaryotic and eukaryotic cells, plus show you the unique characteristics that set these types of cells apart. No need to stress about studying for your next bio test—we’ve got the full breakdown of prokaryotes vs. eukaryotes!

Things You Should Know

All cells (prokaryotes and eukaryotes) have a cell membrane, cytoplasm, ribosomes, and DNA.
Prokaryotes are small, simple cells with a nucleoid region in place of a defined nucleus. They make up unicellular organisms and reproduce through binary fission.
Eukaryotes are large, complex cells that make up multicellular organisms and have a clear nucleus in a membrane. They reproduce through mitosis or meiosis.

Section 1 of 3:

Cell Similarities

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All cells have a cell membrane. The cell membrane is what separates the interior of a cell from its outside environment. It’s semipermeable and regulates which substances can enter and exit the cell. The membrane is made of a lipid bilayer (a combination of proteins and phospholipids, or organic compounds that contain phosphates).^{[1]
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- The cell membrane is also called a plasma membrane.
- Some cells, like plant, fungi, and bacteria cells, have a cell wall outside the cell membrane as an extra layer of protection and structure.
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All cells are filled with cytoplasm. Cytoplasm is a fluid, jelly-like substance that fills the interior of a cell. It’s made mostly from water, salts, organic molecules, and a watery fluid called cytosol. A cell’s internal parts and organelles (small structures within a cell that carry out a specific function) are suspended in the cytoplasm.^{[2]
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- In eukaryotic cells, structures like the nucleus and mitochondria are separated from the cytoplasm by a membrane.
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All cells contain ribosomes. Ribosomes are structures that bind amino acids together into proteins and carry out genetic instructions from the cell’s DNA. All ribosomes are made of 2 subunits (a larger one and a smaller one). Prokaryotic subunits are smaller than eukaryotic ones and are labeled 50-S and 30-S by biologists. Eukaryotic subunits are labeled 60-S and 40-S.^{[3]
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- In prokaryotes, the ribosomes float freely in the cytoplasm throughout the cell.
- In eukaryotes, the ribosomes are bound by a membrane and are typically found in the cytoplasm, endoplasmic reticulum, or covering the nuclear membrane.
  - The endoplasmic reticulum is a network of tubes in the cytoplasm attached to the nuclear membrane.
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All cells encode their genetic information in DNA molecules. Deoxyribonucleic acid (DNA) tells the cell to create RNA (ribonucleic acid) molecules that interact with ribosomes to create proteins and perform other functions. Prokaryotic DNA is simple, circular, and needs a lot fewer genes to function than in a eukaryotic cell. The one circular DNA molecule might be accompanied by smaller DNA circlets called plasmids and is not organized into chromosomes.^{[4]
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- Eukaryotic DNA is linear and complex. It contains packaging proteins called histones and is organized into chromosomes for sexual reproduction.

Section 2 of 3:

Prokaryote-Specific Traits

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Prokaryotes are simpler and less organized than eukaryotes. Besides their outer cell membrane, there are no interior membranes that organize the structures inside the cell. Proteins, DNA, metabolites, and other primitive organelles are all mixed together, floating throughout the cytoplasm.^{[5]
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- Some bacteria cells do have cellular regions or micro-compartments, even if there are no interior membranes to formally separate them.
- The difference is organization between prokaryotes and eukaryotes is so clear that you can easily see the difference through a microscope.
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Prokaryotes don’t have a distinct or bound nucleus. Instead, they have a region called the nucleoid where free-floating DNA molecules gather. The nucleoid does not have a membrane holding it together and is open to the rest of the cell and other interior structures in the cytoplasm.^{[6]
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Prokaryotes are single-celled (unicellular) organisms. This means that one single prokaryotic cell can carry out all of the functions it needs to survive and reproduce. It doesn’t depend on other cells to carry out specialized tasks or to provide genetic information for reproduction.^{[7]
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- Prokaryotic cells can be split into 2 domains of single-celled organisms: bacteria and archaea.
- Archaea are similar to bacteria, but followed a different evolutionary path. Many are found in harsh environments and are known as extremophiles.
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Prokaryotes are usually 0.1-5 μm (micrometers) long. This is incredibly tiny—one micrometer is equal to 0.001 mm (0.000039 in). Prokaryotes are smaller than eukaryotes because they lack internal organization and don’t have specific energy-producing organelles, like mitochondria, to power them. The largest prokaryotes are only half the size (at most) of the smallest eukaryotes.^{[8]
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Prokaryotes reproduce asexually through binary fission. Asexual reproduction means a cell can replicate itself without the genetic information of a different partner cell. During binary fission, the cell’s DNA duplicates itself and organizes itself into 2 identical units. Then, the cell separates to form 2 daughter cells, each with its own set of identical DNA.^{[9]
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Prokaryotes first appeared around 3.5 billion years ago. They were the first living cells scientists know of and formed only 750 million years after the Earth did! They get their name from the Greek karyon, which means kernel or nucleus, and the prefix “pro” which means “before.” Their name reflects how they came into existence before cells had clearly defined nuclei.^{[10]
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- Remember that prokaryote means “before nucleus” when you’re studying for your bio test. This is the biggest difference between them and eukaryotes.

Section 3 of 3:

Eukaryote-Specific Traits

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Eukaryotes are complex, organized cells with internal divisions. Eukaryotes contain more advanced organelles than prokaryotes, each with their own specific function to help the cell live and reproduce. Many of the organelles are encased in their own membrane that separate them from the cell’s cytoplasm. These membranes provide a high level of structure inside the cell.^{[11]
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- Mitochondria (the “powerhouse of the cell”) that produce chemical energy energy for the cell by making adenosine triphosphate (ATP) molecules
- The endoplasmic reticulum (a network of membrane tubes throughout the cytoplasm) that helps transport proteins throughout the cell
- The Golgi apparatus (a stack of small, flat sacs inside the cytoplasm) that produces protein and fat molecules for the cell to use
- Lysosomes that help the cell get rid of waste
- Chloroplasts that produce energy through photosynthesis in plant cells
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Eukaryotic cells contain a distinct, bound nucleus. All of the cell’s DNA molecules are contained in the nucleus by an envelope made of 2 lipid membranes. Lipids are organic molecules like fats, hormones, oils, and more that store energy and provide cellular structure. Having a formal, bound nucleus is the most basic distinction between prokaryotes and eukaryotes.^{[12]
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Eukaryotes make up multicellular organisms, but can also be unicellular. All multicellular animals, plants, and fungi are composed of eukaryotic cells that specialize in specific tasks, like oxygenating blood or fighting viruses. However, there are some single-celled organisms that are eukaryotes, too. For example, yeast (from the fungi domain) and algae (from the protist domain) are eukaryotes.^{[13]
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Eukaryotes are typically 10-100 μm (micrometers) long. On average, eukaryotes are at least 10 times bigger than prokaryotes. This is because they contain much more DNA and internal structures. They also have specialized energy-producers (mitochondria) that can produce enough energy to power a cell significantly larger than a prokaryote.^{[14]
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- Even though eukaryotes are much larger than prokaryotes, you still need to use a microscope to see them.
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Eukaryotes reproduce through mitosis or meiosis. Mitosis is the asexual division of a cell into 2 identical daughter cells—it’s similar to prokaryotic binary fission, but takes longer because of the developed nucleus and helps parts of multicellular organisms grow. For example, your muscle cells underwent mitosis while you were growing so you could reach your adult size.^{[15]
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- Meiosis occurs when sex cells (like sperm and eggs) divide with incomplete DNA and fuse with another sex cell to complete a set of chromosomes.
- Meiosis ensures genetic variety in a species. In meiosis, the daughter cells are not identical to their parent cell (like in mitosis or binary fission).
- Some single-celled eukaryotes, like algae, can reproduce asexually, sexually, or both. All prokaryotes can only reproduce asexually.
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Eukaryotes evolved from prokaryotes about 1.5 billion years ago. The prefix “eu” means “true,” signifying that eukaryotes were the first cells to have a true nucleus. Biologists think eukaryotes evolved from prokaryotes that merged together in a symbiotic relationship since the mitochondria in eukaryotic cells today resemble prokaryotes in structure.^{[16]
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- A symbiotic relationship (symbiosis) is an interaction between 2 separate organisms that benefits the survival of both “partners.”^{[17]
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