Diagram showing the translation of mRNA and the synthesis of ..

The function of the ribosomes in the cell is to translate the genetic information in form of mRNA into proteins. The mRNA is transcribed from DNA using an enzyme called RNA polymerase. To do this, the ribosome requires the presence ofadaptor molecules, the so called transfer RNAs (tRNAs). The tRNAs are small RNA molecules with a defined 3D structure. The tRNAs are charged with the correct amino acid by specific enzymes called aminoacyl-tRNA synthetases. When correctly charged, they function as adaptors between a three-base mRNA codon and the corresponding amino acid.

Translation: Making Protein Synthesis Possible - …

The main stages of protein synthesis are transcription and translation.

Transcription and Translation - YouTube

The above is a grossly oversimplified sketch of the translation process as it applies in a . See Karp for a more detailed treatment. The essentials that this illustration seeks to convey are that the ribosome uses the detailed sequence of codons on the and matches those codons to molecules which carry the corresponding amino acids. The translation process builds a polypeptide with the precise sequence of amino acids specified by the mRNA pattern. In , the translation process has many similarities but is of even greater complexity.

Protein biosynthesis - Wikipedia

The process of translation can be divided into the stages of initiation, elongation, and termination. Initiation involves at least three other proteins called initiation factors to help bind the mRNA to the smaller subunit of the two-unit ribosome. It is bound to the correct location using the initiation codon AUG on the mRNA. The next phase is elongation, or adding other amino acids to the building polypeptide chain. According to Karp, a step of elongation can be accomplished in about 1/20 second, so a small protein of 400 units could be assembled in about 20 seconds! It is suggested that most of this time is used sampling the amino-acid-carrying tRNAs in the cytosol to find the ones for which there is a codon-anticodon match for the next codon along the mRNA pattern.

That is, the two processes, transcription and translation, are temporally and spatially separated.
Ribosome may dissociate from the mRNA at the end of translation of a polypeptide, or stay on the mRNA and continue translating the next CDS.

a complete ribosome and the protein synthesis is ..

The "front" end of the mRNA is referred to as the 5' untranslated region (5' UTR) and the sequence at the "back" end is called the 3' untranslated region (3' UTR).

In prokaryotes, however, translation begins before transcription is finished (they occur simultaneously) and they occur in the same place.

Protein Synthesis Flashcards | Quizlet

Which amino acid that is going to be incorporated into the growing peptide chain is determined by the codon (a triplet of bases) on the mRNA (fig 2). Many amino acids have several codon options, so each amino acid can be incorporated by a set of different codons. For example, the amino acid lysine has two codons and serine has 6 different codons. Codons for the same amino acid tend to have the same nucleotides for the two first positions and only differ in the third position. Only two amino acids, tryptophan and methionine, have one single codon. The codon for methionine is also a start signal for protein synthesis. There are also several stop codons, which are used as a signal when the protein message is ending. These are decoded not by a tRNA but by a protein called release factor.

These three bases are unique for each tRNA and (as we will see) hydrogen bond to the codon of the mRNA during translation.

Making protein is the goal of translation

The polypeptide chain is transferred from the P-site tRNA to the free amino group of the amino acid attached to the A-site tRNA, forming a new peptide bond. This reaction is catalysed by the peptidyl transferase center of the large ribosomal subunit. This reaction is followed by a series of large conformational changes, which shift the two tRNAs into the P and E sites of the large subunit, so the tRNA which previously was in the A-site is now in the P-site and the E-site is bound with the former tRNA of the P-site. Through large conformational changes catalysed by the protein EF-G, the mRNA moves by three nucleotides with respect to the the small ribosomal subunit together with the tRNAs so that the ribosome is ready to enter the next round and accept a new tRNA. These three steps are repeted in a so-called until the ribosome reaches a stop codon, where synthesis is stopped and the protein chain is released. Procaryotic ribosomes are remarkably efficient: within a bacterial cell, one ribosome can add 20 amino acids to a growing polypeptide chain every second.

The ribosome is helped both at the start and end of translation by specialized proteins called initiation factors and release factors, respectively.