There are several differences between the prokaryotic cells and eukaryotic cells, however depending on the internal structure of the cell, prokaryotic cells are simple, unicellular, and small that does not have a well-defined nucleus whereas eukaryotic cells are multi cellular, larger, and have a well-defined nucleus.
An evolution from prokaryotes to eukaryotes
Prokaryotic cells are the most ancient kind of cells that were found in the Three Domain System that includes bacteria and archaeans.
Many prokaryotes such as bacteria can be found almost anywhere living in our body and are able to thrive in a starvation environment when enough nutrients are not available. Archaeal cells are another example of prokaryotic cells that are similar in size and shape to bacteria and are also composed of single-cell and are found in extreme environments such as hot springs, soils, oceans, marshlands, and inside the body of other organisms.
Millions of years ago prokaryotes were the only existing life on earth until 1.5 to 2 billion years back, when fossil records indicate that eukaryotic cells are evolved from prokaryotic cells that joined together in a symbiotic union.
Many scientists believe that eukaryotic cells are a result of small changes in the structure and function of existing prokaryotic cells through the process of evolution. It can be said that probably the first eukaryotic cell was miraculously born from prokaryotic, symbiotic, and multicellular interactions.
Comparison Chart
| Basis | Prokaryotic Cells | Eukaryotic Cells |
| Cell Type | Usually composed of single-cell (some species of cyanobacteria may be multicellular) | Multi-cellular |
| Number of chromosomes | One (but not true called as a plasmid) | More than one |
| Cell size | Size of the cell is small (1-10 micrometers) | Larger (10-100 micrometers) |
| Cell wall | Usually present but chemically complex ( composed of peptidoglycan or mucopeptide) | Usually cell wall absent only present in plant cells and fungi (chemically simpler composed of cellulose and chitin) |
| Nucleus | True nucleus (well-defined nucleus) is absent. Nucleus lack nuclear membrane and nucleolus called as nucleoid | A well-defined nucleus is present bounded within nuclear membrane and nucleolus |
| Mitochondria | Absent | Present |
| Endoplasmic Reticulum | Absent | Present |
| Ribosome | Made of smaller subunits 30-S and 50-S and are distributed in the cytoplasm | In eukaryotic cells, ribosomes are more complex and made of bigger sub units 70-S and 80-S and bound by a membrane |
| Cell division | Binary fission (conjugation, transformation, and transduction) | Mitosis |
| Mode of reproduction | Asexual | Sexual (involves meiosis) |
| Organelles | Organelles are not membrane-bound (if present any) | Organelles are membrane-bound and are specific in function |
| Cytoskeleton | Absent | Present |
| Duration of cell cycle | Short ( 20-60 minutes) | Long (12-24 hours) |
| Transcription and Translation | Occurs at the same time | First transcription occurs in nucleus then translation occurs in the cytoplasm |
| Metabolic mechanism | Wide variation | Krebs cycle, electron transport chain |
| Lysosomes and peroxisomes | Absent | Present |
| Flagella | Simple structure ( submicroscopic in size composed of protein and flagellin) | Complex (usually arranged as 9+2 surrounding two singlets of tubulin and other protein) |
| Example | Archaea and bacteria | Plants and animals |
What are Prokaryotic Cells?
Prokaryotic cells are the smallest, simplest, and most ancient cells and the organisms made from these cells known as prokaryotes.
Characteristics of Prokaryotes
Prokaryotes are unicellular organisms that do not have a true nucleus as the DNA is not contained within a membrane or separated from the rest of the cell known as nucleiod.
All prokaryotic cells have a nucleoid region that contains DNA and RNA as their genetic material, ribosomes that are the sub-units of proteins, and cytoplasm that contains a cytoskeleton that helps in supporting the other parts of the cell.
Prokaryotic cells usually range between 0.1 to 5 micrometers in length and have a higher surface area/ volume ratio which makes them able to obtain a larger amount of nutrients via the plasma membrane.
Components of Prokaryotic Cells
Prokaryotic cells are not as complex as eukaryotic cells and can be seen in varying shapes and sizes.
There are four main components of prokaryotic cells:
Plasma Membrane
A plasma membrane also called a cell membrane is an outer covering that surrounds the cell’s cytoplasm and helps in regulating the flow of substances into and out of the cell.
Cytoplasm
The cytoplasm is a gel-like fluid composed mainly of water, enzymes, and salts in which all of the other cell components are suspended. The cytoplasm is the region found outside the nucleus but inside the plasma membrane.
Ribosomes
Ribosomes found in prokaryotic cells are smaller and have a slightly different shape and composition than those found in eukaryotic cells. Despite the differences, the function of ribosomes is to build proteins by translating messages sent from DNA in both types of cells.
Genetic Material
In prokaryotic cells, genetic material is found in large quantities in the form of DNA and RNA because the prokaryotic cell does not have a well-defined nucleus so a chromosomal DNA tends to look like a mess of string in the middle of the cell containing most of the genes needed for cell growth, survival, and reproduction.
What are Eukaryotic Cells?
Eukaryotic cells are larger and complex cells that possess a clearly defined nucleus, organelles, and are enclosed by a plasma membrane.
Organisms that are composed of eukaryotic cells are known as eukaryotes that include protozoa, fungi, plants, and animals.
Characteristics of Eukaryotes
Eukaryotic cells contained a variety of sub cellular structures called organelles that play an important role in energy balance, gene expression, and metabolism.
Unlike prokaryotic cells in which DNA is loosely bound in the nucleoid region, eukaryotic cells possess a nucleus and are surrounded by a complex nuclear membrane that separates the inside of the cell from the outside environment.
Components of Eukaryotic Cells
Alike prokaryotic cells, eukaryotic cells also have a plasma membrane, cytoplasm, and ribosomes. However, unlike prokaryotic cells, these cells have a:
- Membrane-bound the well-defined nucleus
- Numerous membrane-bound organelles ( Mitochondria, Golgi apparatus, Chloroplasts, and Endoplasmic reticulum)
- Several rod-shaped chromosomes
Key Differences between Prokaryotic Cells and Eukaryotic Cells
- All eukaryotic cells have a separately enclosed nucleus inside the cell’s cytoplasm whereas prokaryotic cells do not have a true nucleus.
- All eukaryotic cells contain a cytoskeletal structure but on the other hands, prokaryotes do not have them.
- Cell production in eukaryotic cells occurs via mitosis ( a process in which the chromosomes divide by using components within the cytoskeleton) however in prokaryotic cells divide by binary fission.
- All eukaryotic cells have cell walls whereas cell walls are absent in prokaryotic cells.
Comparison Video
Conclusion
Prokaryotic cells are the most ancient cells that were found millions of years ago in the most primitive life on earth including bacteria and archaeon species however eukaryotic cells are more complex and larger evolved as a result of mutation in prokaryotic cells.