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The Process of Protein Synthesis

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Process of Protein Synthesis Task 1 (1a) DNA: RNA: RNA has a single polynucleotide chain where as DNA has a double polynucleotide chain, RNA has 3 basic forms t, m, r, and DNA has 1 form only; in RNA the molecular mass is smaller than in DNA as DNA has a greater molecular mass. In RNA it has nitrogen containing bases which are adenine, guanine, cytosine and thymine however this is different to DNA as DNA has a nitrogen containing bases which are adenine, guanine, and cytosine but instead of thymine it contains uracil. RNA contains Ribose sugar whereas DNA's sugar in deoxyribose and RNA occurs in nucleus and cytoplasm, but DNA occurs almost entirely in nucleus; RNA maybe chemically unstable unlike DNA which is always chemically stable as RNA only exists for a short period of time unlike DNA which exists permanently. (1b) DNA RNA * DNA is vital for inheritance, coding for proteins and the genetic blueprint of life. * There are three bases in DNA code for one amino acid. * * The DNA code is copied to produce mRNA; the order of amino acids in the polypeptide is determined by the sequence of 3-letter codes in mRNA. tRNA mRNA * tRNA (transfer RNA) is a type of RNA that delivers amino acids to ribosomes during translation in the order specified by the mRNA. * tRNA pulls the amino acids into the rRNA (ribosome) ...read more.


There are 61 codons that specify the amino acids used in proteins and 3 codons known as stop codons which signal the termination of growth of the polypeptide chain which mean there are 64 in total; there are 64 codons because there are four bases and three bases per codon. Code is a triplet code because there are three different unique amino acid codes that make up that codon by following a certain sequence, the amino acids then combine into three to form a DNA or RNA strand (hence the name triplet). Start and stop codons: A start codon is the message that starts a certain protein being synthesized from a certain sequence and stop codons are the messages that tell the cell that the protein is made and that it should stop adding more amino acids to the polypeptide. Degeneracy is basically things that are different structurally but create the same results; some codons (3 nucleotides that code for an amino acid during translation) may code for the same amino acid for example argentine, multiple codons can code for that specific amino acid but for polypeptides, however changing those specific codons may give the same result. If argenine was coded with CGU and was changed to CGC both these results may still produce the amino acid argentine which means the polypeptide didn't change however the genetic code did change this is known as the wobble effect. ...read more.


can simultaneously translate the same mRNA molecule. tRNA brings specific amino acid to ribosome and mRNA carries the genetic information to protein, the codons that encode the same amino acid often differ slightly but only by their third base; the joining of the third base is less stringent than the other two, because of this differentiation one tRNA can pair with multiple mRNA codons. There are signal sequences before the main coding sequence at the translation initiation sites, amino acid activation is catalyzed by amino acyl-tRNA synthetase and pairs it to its corresponding tRNA; anti codon in the tRNA molecule forms base pairs with the appropriate codon on the mRNA. In the initiation step initiation factors are involved; the initiation factor is the protein that promotes the association of ribosome's with messenger RNA, in the elongation step incorporation of an amino acid into a protein takes place as a result of this a polypeptide chain is grown then the termination stage is the last stage in protein biosynthesis. This diagram represents the basic process of Bio - synthesis of proteins... Basically protein synthesis is simply the method that takes place in order to produce proteins; a protein is simply a long chain of amino acids linked together by bonds which have been previously produced and formed from the two stages of protein synthesis known as transcription and translation, the research carried out on protein synthesis shows that protein synthesis is a highly important process that is required for correct bodily functioning and not just physically but mentally as well. ...read more.

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*** A set of unknown tasks on DNA, RNA and protein synthesis which the student has spent some time completing to a good standard of presentation. Unfortunately some task answers have suffered due to an over reliance on website information, used wholesale and the facts being conveyed in a less than logical sequence.
To improve
It would have been helpful to know what the tasks set were to know whether the student had completed the task correctly.
The student needs to take greater care with the use of key terms. Amino acids and nucleotide bases were often confused. Amino acids was used when it should have been amino acid residues. Nitrogen used instead of nitrogen atoms. DNA was "copied".

The candidate needs to read through answers to ensure that the sentences are clear and concise.
The section on protein synthesis was poor, because of an overreliance on website sources that had not been modified and were pasted in their entirety. The candidate must use references carefully and write the answer in their own words since it was clear they did not fully understand what they were writing about and the linkages between paragraphs were unclear.
The best responses follow a clear line of logic and make a series of simple statements to start with along the lines of ?antibodies are proteins?, ?proteins are synthesised in the ribosomes?, etc.

Marked by teacher Stevie Fleming 26/07/2013

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