Introduction: Prokaryotes And Eukaryotes
Biotic components of the environment include all forms of life from minute bacteria to towering giant sequoias. But at the microscopic level, all living organisms are made up of cells. As a result, the cell is referred to as the structural and functional unit of all living organisms. The word cell has its origins from 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.
Pictured: 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 cell and eukaryotic cell, 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.
Difference between Prokaryotic and Eukaryotic cells
One of the most ancient groups of living organisms on earth is the Prokaryotes, with fossil records being dated 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.
Common examples of Prokaryotic organisms are bacteria and archaea. Examples of eukaryotes include almost every unicellular organism with a nucleus and all multicellular organisms. Though these two classes of cells are quite different, they do possess some common characteristics. For instance, both posses cell membrane and ribosomes.
The term “prokaryote” is derived from the Greek word “pro”, (meaning: before) and “karyon” (meaning: kernel). It translates to “before nuclei.” Prokaryotic cells are comparatively smaller and much simpler than eukaryotic cells. The other defining characteristic of prokaryotic cells is that it does not possess a nucleus or other membrane-bound cell organelles. Reproduction happens through the process of binary fission.
Structurally, prokaryotes have a capsule enveloping its entire body, and it functions as a protective coat, 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 and resist 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 a vital role in protein synthesis. It is also one of the smallest components within the cell.
Some prokaryotic cells contain special structures called mesosomes which help in cellular respiration. Most prokaryotes also contain plasmids, which contains small, circular pieces of DNA. And to help with locomotion, flagella are present, though, pilus can also serve as an aid for locomotion. All members of Kingdom Monera are prokaryotes
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 the prokaryotes. They include almost all the major kingdoms except kingdom monera. Structurally, eukaryotes consist of the cell wall which protects and supports the plasma membrane. The plasma membrane surrounds the cell 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 vital 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. 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, Golgi bodies, lysosomes, vacuoles, cytoplasm, chromosomes, and centrosomes.
Difference between Prokaryotes and Eukaryotes Table
|Type of cell||Always unicellular||Unicellular and multi-cellular|
|Cell size||Size lies in between 0.2- 2.0 μm in diameter||Size lies in between 10 – 100 μm in diameter|
|Cell wall||Usually present; chemically complex in nature||When present, chemically simple in nature|
|Ribosomes||Present. Smaller in size and circular in shape||Present. Larger in size and linear in shape|
|Cytoplasm||Present, but cell organelles absent||Present, cell organelles present|
|Plasmids||Present||Very rarely found in eukaryotes|
|Ribosome||Small ribosomes||Large ribosomes|
|Lysosome||In this, the lysosome, mesosome, and centrosome is absent||Mesosome, Lysosomes, and centrosomes are usually present in Eukaryotes|
|Cell division||Through binary fission||Through mitosis|
|Nucleus||Absent||Present, bounded by a double membrane|
|Flagella||The flagella are smaller in size||The flagella are larger in size|
|Reproduction||Asexual||Both asexual and sexual|
|Example||Bacteria and Archaea||Plant and Animal cell|
Questions about Prokaryotic and Eukaryotic cells
1. 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.
2. What is a eukaryotic cell?
Eukaryotic cells are cells that possess a true nucleus along with membrane-bound organelles. Eukaryotes are can either be unicellular or multicellular.
3. What is the difference between prokaryotic and eukaryotic cell?
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. Other major differences between prokaryotic and eukaryotic cells are that prokaryotic cells are exclusively unicellular, while the same does not apply for eukaryotic cells.
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