3.5.4 Explain the process of Translation leading to polypeptide formation
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3.5.4 Explain the process of
3.5.4 Explain the process of Translation, leading to polypeptide formation
Translation is the second stage in the process of protein synthesis where a piece of mRNA (formed in Transcription) is used to create a polypeptide chain.
Key terms:
mRNA (messenger RNA) is made up of codons
tRNA (transfer RNA) contains an anticodon which defines the specific amino acid carried by the tRNA
Translation takes place in the cytoplasm and the first thing that happens is that the ribosome attaches to the mRNA at the start codon (always AUG). The ribosome is made up of rRNA (ribosomal RNA) and ribosomal protein. The ribosome has an 'A' site (consider this like an attachment site) and a 'P' site (consider this like a parking site).
A piece of tRNA with an anticodon complimentary to the start codon on mRNA comes from the cytoplasm, carrying a specific amino acid, to attach at the start codon in the 'P' site. The first amino acid is always Methionine.
A second piece of tRNA with an anticodon complimentary to the second codon on mRNA comes from the cytoplasm, carrying a specific amino acid, to attach to the second codon in the 'A' site. In this case the second amino acid is Tyrosine.
A covalent peptide bond forms between the two amino acids. The ribosome moves along the mRNA by one codon. The second tRNA is now in the 'P' site and the 'A' side is free. The first piece of tRNA is now free to leave as its amino acid is now bonded to the second amino acid (whose tRNA is in the 'P' site). With the 'A' site free a new tRNA (with an anticodon complimentary to the next/third codon on the mRNA) is able to float in from the cytoplasm and attach at the 'A' site on the ribosome. The amino acid carried by this tRNA attaches to the existing chain with a peptide bond.
Note that the amino acids used are specific and defined by the codons on the mRNA and associated complimentary anticodons on mRNA.
This process continues until the Ribosome reaches a 'Stop' codon on the mRNA. The 'Stop' codon does not code for an amino acid but indicates where the process of translation should terminate.
One the process has terminated the polypeptide chain, tRNA, ribosome and mRNA all detach and the polypeptide chain become free-floating in the cytoplasm. Thus we have used a piece of mRNA to ultimately form a polypeptide chain.
Translation is the second stage in the process of protein synthesis where a piece of mRNA (formed in Transcription) is used to create a polypeptide chain.
Key terms:
mRNA (messenger RNA) is made up of codons
tRNA (transfer RNA) contains an anticodon which defines the specific amino acid carried by the tRNA
Translation takes place in the cytoplasm and the first thing that happens is that the ribosome attaches to the mRNA at the start codon (always AUG). The ribosome is made up of rRNA (ribosomal RNA) and ribosomal protein. The ribosome has an 'A' site (consider this like an attachment site) and a 'P' site (consider this like a parking site).
A piece of tRNA with an anticodon complimentary to the start codon on mRNA comes from the cytoplasm, carrying a specific amino acid, to attach at the start codon in the 'P' site. The first amino acid is always Methionine.
A second piece of tRNA with an anticodon complimentary to the second codon on mRNA comes from the cytoplasm, carrying a specific amino acid, to attach to the second codon in the 'A' site. In this case the second amino acid is Tyrosine.
A covalent peptide bond forms between the two amino acids. The ribosome moves along the mRNA by one codon. The second tRNA is now in the 'P' site and the 'A' side is free. The first piece of tRNA is now free to leave as its amino acid is now bonded to the second amino acid (whose tRNA is in the 'P' site). With the 'A' site free a new tRNA (with an anticodon complimentary to the next/third codon on the mRNA) is able to float in from the cytoplasm and attach at the 'A' site on the ribosome. The amino acid carried by this tRNA attaches to the existing chain with a peptide bond.
Note that the amino acids used are specific and defined by the codons on the mRNA and associated complimentary anticodons on mRNA.
This process continues until the Ribosome reaches a 'Stop' codon on the mRNA. The 'Stop' codon does not code for an amino acid but indicates where the process of translation should terminate.
One the process has terminated the polypeptide chain, tRNA, ribosome and mRNA all detach and the polypeptide chain become free-floating in the cytoplasm. Thus we have used a piece of mRNA to ultimately form a polypeptide chain.
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در تاریخ 1391/01/20 منتشر شده
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