To understand what is translation in Biology, it is important to know the basis of its requirement. Now, it is quite well-known that the basic unit of a living organism is a cell. In the same manner, it is also clearly understood that the molecular basis that forms the fundamental unit of all living organisms is most widely the Deoxyribo-Nucleic Acid - DNA. DNA contains almost all the information required for an organism to carry out all the biological, biochemical and biophysical processes throughout its life cycle.
Interestingly, DNA is not directly involved in carrying out the biological processes inside a cell. That work is mostly carried out by the protein and huge complexes they are able to form a bunch of proteins for more complex multicellular organisms like human beings. These proteins are created from the information encoded within the DNA. And the two major processes required for the information contained in the strands of DNA to be converted into the functioning proteins are - Transcription and Translation.
Central Dogma in Molecular Biology
The central dogma of molecular Biology is the main principle explanation of how the information flows in molecular Biology. Generally stating, the central dogma says that:
Deoxyribo-Nucleic Acid (DNA) makes Ribonucleic Acid (RNA) and RNA makes protein.
This rule is universally true in most cases.
Thus, the central dogma clearly states that the information is passed from the DNA to RNA and from RNA to protein. As mentioned above, there are two processes which carry out this transfer of information - Transcription and Translation. Hence, we can say that Transcription is what makes the information flow from DNA to RNA and Translation is what makes the same information received in the form of RNA, to flow to proteins. Thus, it can be said, the process of protein manufacturing or protein synthesis is called Translation.
The process Translation is given below in more detail.
Translation is the process of polymerisation of amino acids to form a chain of polypeptides. The amino acids are the structural units of proteins and these polypeptides are essentially proteins and protein complexes. The order and sequence of the polymerisation of the amino acids are defined by the sequence of the nucleic acid bases in the messenger RNA (mRNA).
Components of Translation
The process translation is generally carried out inside the ribosomes, an organelle of the cell. These ribosomes are equipped with ribosomal RNA, structural RNAs and about 80 important proteins. Owing to the importance of ribosomes, in protein synthesis i.e. carrying out the process of translation, ribosomes are called the manufacturing unit of the cell.
The ribosomes facilitate the formation of the polypeptide bond of the amino acids. They serve as the platform where different tRNA molecules carrying specific amino acids and energy molecules such as ATP and GTP, come together in an enclosed space, and since they are near to each other energetically favourable conditions occur for the formation of polypeptide chains of the amino acids.
Another function of the ribosome is also to act as a catalyst for the formation of the peptide bond. Various enzymes in the ribosomes act upon the interacting tRNA and amino acid molecules playing a vital role in the passing of the information from RNA to the proteins and efficiently utilising the energy molecules to carry out the reactions. In unicellular organisms also [such as bacteria, 23S ribosomal RNA known as the ribozymes], it serves as a catalyst.
Stages of the Translation Process
The process translation utilizes the components of translation during the following three stages.
Initiation: For initiation, the ribosome binds to the mRNA. This binding happens at the start codon - a stretch of three nucleobases namely Adenine, Uracil and Guanine (AUG). This starting code is only recognised by the initiator tRNA which carries the methionine amino acid with it. Hence, usually in most cases, the sequence of a protein starts with methionine.
Elongation: This stage is characterised by the addition of amino acids one by one and the formation of a polypeptide chain in a sequence determined by the DNA and represented by the RNA. In this stage, complexes made up of amino acids bound to tRNA sequentially attach to the next in line three pairs of nucleobase or called as codons on the mRNA and the ribosome moves from codon to codon on the mRNA producing the polypeptide.
Termination: In this last stage, a release factor binds to the stop codon, and termination of translation and releasing the complete polypeptide from the ribosome.
The entire process of translation can be summarized as follows in the given diagram:
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Thus, translation is the process of the flow of information from RNA to proteins, wherein complex machinery of proteins and ribosomes is involved in the production of proteins.