Translation is a microscopic process within living cells that results in protein synthesis. There are two types of cells that comprise living organisms: prokaryotic and eukaryotic.
Prokaryotic cells are actually unicellular organisms, meaning that an entire life form is comprised of only one cell. For example, a single-celled bacterium would be a prokaryotic organism. These are generally viewed as being very simplistic organisms in terms of organization. They do not have large membrane-bound organelles, like a nucleus. However, they do have macromolecules such as ribosomes.
Eukaryotic organisms, on the other hand, are almost exclusively multicellular. This means that people, animals, plants, and other complex eukaryotic organisms are made up of several cells working together. There are more processes, organelles, and functions involved in these types of organisms. Since these life forms are more complex than bacteria, that also means the parts within a eukaryotic cell are more complex than the parts in a prokaryotic cell. These types of cells have both membrane-bound organelles and macromolecules within the cytoplasm.
Despite the differences between prokaryotic and eukaryotic cells, they also have several similarities.
Both types of organisms have DNA, ribosomes, proteins, and other specific materials that allow the cells to carry out functions conducive to life. One of these processes is called translation. It can be found in both types of cells.
What is translation?
Translation is a step in protein synthesis where mRNA is decoded into a specific sequence of amino acids, which are the building blocks of proteins.
It occurs in three steps: activation, initiation, elongation, and termination.
The process begins with a start codon that signals where translation of the mRNA strand should begin. When the process reaches a stop codon engrained in the mRNA strand, the process is terminated and that set of amino acid formation is complete. Then, the process begins again, possibly to form different amino acids for different processes in the body. This is incredibly important, because nearly every system in living organisms rely on proteins. Without them, cells could not carry out a single function conducive to life.
Similarities between Prokaryotic and Eukaryotic translation
- Template: DNA (either in the nucleus or free-floating) is transcribed into mRNA, which is a template that organelles can understand. Once the cell has synthesized mRNA strands, both prokaryotes and eukaryotes can translate these new strands into amino acids within a ribosome.
- Start site: A strand of mRNA has two ends: a 3’ and a 5’ end. Both types of cells always begin translation on the 5’ end of mRNA and move towards the 3’ end. This is true for most processes in living cells, but there are a few exceptions.
- Location: Transcription and translation occur simultaneously in prokaryotes, but the singular act of translation happens within a ribosome in the cytoplasm. Eukaryotes break down the processes into two different steps, but translation still always happens in the cytoplasm of a cell where ribosomes are freely available.
- Ribosomes:These macromolecules are the site of protein synthesis in all living cells. More specifically, translation occurs inside of these small organelles. They are most often found floating freely within the cytoplasm of a cell, though they can attach to membrane-bound organelles if present.
- Codons: Both types of cells use the same 61 types codons during translation, including those that signal the beginning and end of translation. Without these, translation would not have a starting or stopping point.
- Initiation codon: Translation begins in the ribosome by reading the mRNA strand. The strand must have an initiation codon that tells where translation should start. In both types of cells, translation begins where the codon AUG is present on the mRNA strand.
Differences between Prokaryotic and Eukaryotic translation
- Life span of mRNA: mRNA is the template for translation. While it generally looks the same in prokaryotes and eukaryotes, the lifespan differs greatly. Prokaryotes are lucky if the mRNA life span lasts longer than a few minutes. On the other hand, eukaryotic mRNA is quite stable and lasts anywhere from hours to a few days. This is good to remember when thinking about the differences in the speed of translation between prokaryotic and eukaryotic cells.
- Types of ribosomes: Prokaryotic translation occurs in 70S ribosomes, which are quite small. Eukaryotic translation occurs in larger 80S ribosomes.
- Type of mRNA: When translation happens in a prokaryotic cell, the initial mRNA strand is called polycistronic. This means that the mRNA codes for more than one protein and has many start and stop codons. The cell must differentiate between these in order to find the segment needed for translation. Conversely, eukaryotic cells translate from monocistronic mRNA. This type of mRNA only codes for a single protein, making the process more straightforward than in prokaryotes .
- Speed: Prokaryotic cells translate about twenty amino acids per second, while eukaryotic cells usually translate only one amino acid per second. This means that translation in a prokaryotic cell is much faster than in a eukaryote. The timing of this process parallels the life span of mRNA in either prokaryotic or eukaryotic cells.
Tabular Comparison of Prokaryotic and Eukaryotic Translation
|mRNA life span||Shorter||Longer|
|Type of mRNA||Polycistronic||Monocistronic|
Translation is a very important process found in both prokaryotic and eukaryotic cells. While there are many differences in translation between prokaryotic and eukaryotic cells, both result in the formation of amino acids essential for protein synthesis. Proteins fuel every single function in living cells. Without them, those processes could not occur and life could not exist.
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