Protein Synthesis

Topics: DNA, RNA, Protein Pages: 7 (2335 words) Published: August 25, 2013
The Earth has a plethora of organisms that live and reproduce all throughout its surface. Depending on what kind of organism, they go through some processes that others life-forms do not need to do. However, the molecules DNA and RNA, which are found in all living creatures, work together in a certain process that is crucial to existence: the formation of proteins. Although all species differ from each other in various ways, the processes by which proteins are synthesized are the same in all.

Protein synthesis is a very complex process. In order to understand the process, there some basics that are essential for cells to create the proper proteins. DNA is a very long and double-stranded molecule that contains coding, through four nitrogen bases (adenine, guanine, thymine, and cytosine), for all the genetic information needed to control what needs to happen, or be expressed, by that particular cell. This includes which proteins are made in the cell. The information for the protein is retrieved by the RNA. RNA is different from DNA in that it is single-stranded and is made from the DNA. RNA is very important to the process of protein synthesis in that it is the intermediate of the genes from the DNA and the amino acids in proteins for which they code for. There are two main stages of protein synthesis in every organism: transcription and translation. Transcription is the formation of RNA, specifically mRNA, by DNA, while translation is the formation of polypeptides, the monomers or building blocks of protein, by mRNA and transfer RNA (tRNA). The four nitrogen bases of DNA when transcribed into RNA are read in groups of three called codons, which code for specific amino acids. There sixty-four possible combinations of three nitrogen bases that can form codons. All the proteins in bodies are formed from only twenty amino acids stuck together on long polypeptide chains that later become functional proteins (Wu 1). How come there are only twenty amino acids when there are sixty-four possible combinations of codons? That is because codons are redundant in that multiple codon combinations can produce the same amino acid (and three of the possible codon combinations are stop codons that do not code for an amino acid), however codons are not ambiguous. A codon cannot code for more than one amino acid. These same codons and amino acids are possible in any organism, which is why protein synthesis is known to be universal.

As stated in the last paragraph, transcription is the synthesis, or forming of, RNA under direction of the DNA. Transcription takes place in the nucleus, where all the DNA in the cell is stored. There are three stages to the transcription process in the synthesis of a protein. The first stage starts out with the polymerase binding with the promoter on the regions to be transcribed from the DNA to the mRNA. The polymerase signals the DNA helix to unwind to form an opening for the start of mRNA transcription (UM 1). The promoter is located at the beginning of the region that needs to be transcribed, and sends out a signal to the polymerase so that structure knows where to start unwinding the double helix of the DNA. The binding of the polymerase to the promoter forms what is called the transcription-initiation complex. The whole strands of DNA are not necessary for every protein, so this system helps to conserve energy within the cell by only having to unwind part of the DNA and not all of it. Also, the promoter’s signals are mediated by transcription factors that tell the whether transcription itself is even necessary in that region of the DNA. This first part of transcription is known as the initiation stage. In the next stage, elongation, the RNA strand moves inside the opening and transcribes the sequence of the nitrogenous bases to itself. The RNA polymerase moves along the DNA strands, slowly unwinding a few bases at a time as the single RNA strand binds to one of the two strands of DNA from the 5’ side to...

Cited: “Building proteins from the ground up.” The Economist [US] 29 Oct. 1988: 89+. Gale Biography
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Campbell, Neil A., et al. “Gene to Protein” AP Edition Biology. 8e* ed. New York:
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Wu, Corinna. “An alphabet for a letter-perfect protein.” Science News 4 Oct. 1997: 214. Gale
Biography in Context
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