Protein biosynthesis
Protein biosynthesis can be simply defined as the process through which cells are able to build proteins for use by the body. Even though most people use this term in reference to protein translation, however, it should be noted that it is used to define a multi-process that starts with the synthesis of amino acids and transcription. Amino acids are the monomers that undergo polymerization in order to give forth, proteins. However, not all the amino acids can be synthesized by each organism.
In many occasions, proteins can be directly synthesized from genes through the process of MRNA translation. Whenever the body requires proteins on short notice or in large amounts, a precursor for protein is produced. This precursor is called a proprotein. It is basically a protein that is inactive and contains one or more peptides. These inhibitory peptides can undergo activation in a situation whereby the inhibitory sequence has been removed. Preproteins have both the inhibitory and signal sequences.
For protein to be synthesized there has to be a unification of tRNA molecules that are charged with the required amino acids, with an MRNA molecule. Besides, it also has to be matched up through base pairing. In order to extend the growing chain of proteins, the amino acids have to be joined together. The tRNAs on the other hand, have to be released. This entire process is conducted by a large multi-molecular tissue known as the ribosome.
When discussing protein synthesis, it is important to bear in mind that DNA plays a crucial role. However, it only carries genetic information and does not take part in the process whereby the information is being used. The first step involves transcribing the genetic information that is contained therein into a form that can be useful. Either way, the information contained in the DNA can also undergo translation to produce a sequence of amino acids.
Transcription and translation are the two main processes that are involved in protein synthesis. Transcription is the first step that takes place in three phases; initiation, elongation and termination. In order to ensure that gene transcription is done correctly, each of the three stages is controlled by co-activators and transcription factors. This process takes place in the cell nucleus.
Translation is the process through which proteins are synthesized from RNA. It takes place in the cytoplasm, the location for ribosomes. Translation is carried out in four phases; activation, initiation, elongation and termination. At this stage of protein synthesis, amino acids are fixed with tRNA molecules.
Biosynthesis is mainly followed by two events; post-translational modification and folding of proteins. In the process of synthesis and after it, polypeptide chains are often folded into structural units. It is this process that is referred to as protein folding. The task of protein synthesis in the cells begins at the N-terminal end of a polypeptide chain. Before the formation of an active protein, modifications have to be made to the polypeptide.
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Reference:
http://en.wikipedia.org/wiki/Protein_biosynthesis
http://chemed.chem.purdue.edu/genchem/topicreview/bp/1biochem/synthesis9.html