SAT2化学知识解析：Protein Synthesis

      今天新航道SAT频道小编为大家整理了SAT化学知识解析：Protein Synthesis，供大家参考，以下是详细内容。

　　Now, we have described the DNA and RNA, it's time to take a look at the process of protein synthesis. Protein synthesis takes two steps: transcription and translation. Transcription takes the information in the DNA encoding, and encode them into the mRNA, this head slide out of the cell nucleus and into the cytoplasm in. In the translation process, the working principle of the mRNA with a ribosome and tRNA synthesis of protein.

　　Transcription

　　The become the the first a transcriptional Marketing (transcription) step shall not be held in the for the Yes DNA molecules of, on in order to the part of the at the between the of Number of shares in the the Ministry of deoxyribonucleic acid, need of the protein for the verification code can to be transcribed the part of the unwinding of the of the . The mRNA strand acomplementary Once the deoxyribonucleic acid (DNA) molecules is unwound at the correct position, an enzyme called RNA polymerase can help line up to obtain a nucleotide to create . Since the mRNA is a (-) of the single-stranded molecules, the two DNA chain, only a one is used as a template for the new RNA chain.

　　The new chain of RNA. Made according to the base pairing rules:

　　The genomic DNA cytosine guanine RNA

　　The guanine DNA and RNA cytosine

　　DNA and RNA adenine thymine pairs

　　The RNA uracil DNA adenine currency on

　　For example, the mRNA complement to the DNA sequence TTGCAC AACGUG. The SAT II Biology frequently asked is to be produced from a given section of the DNA sequence into a corresponding sequence on the mRNA. For these questions, do not forget that RNA uracil in place of thymine.

　　After transcription, the RNA chain is released, and after the compression of the two solutions of the DNA strands together again to form the double helix. , After transcription remains unchanged because the DNA template, it is possible to, identical to the transcription of RNA to another molecule, immediately after the first one is complete. A single gene on a DNA chain can produce enough of the the RNA, to make thousands within a very short time on the same copy of the protein.

　　Translation

　　Translation, mRNA was sent to the cytoplasm, where it is the ribosome, a protein synthesis website bonds. Ribosome, there are three important of binding sites: one for mRNA and two for aminoacyl tRNA. The two in the aminoacyl-tRNA site are marked for the A site and P site.

　　Once the mRNA is in place), tRNA (RNA molecules, each one with a specific amino acid, binding to the mRNA by ribosomes in a sequence of code defines associated in the aminoacyl tRNA molecules You can perform this function, because of their special structure of the aminoacyl-tRNA is achieved up to many nucleotides, bent into the shape of a cloverleaf in its tail end) tRNA (ribonucleic acid with an acceptor attention to a particular amino acid acid dry, at its head, three nucleotides of the tRNA anticodon.

　　An anti-codon and the mRNA complementary to the nitrogenous bases. For example, if a codon on the mRNA in the AUC, it will work with the aminoacyl-tRNA anticodon sequence UAG pairing. Aminoacyl-tRNA. . Molecules with the same anti-codon sequence will always carry out the same amino acid, to ensure consistency for the protein encoded by the DNA in.

　　The translation process,

　　Translation from the beginning of the chain with the binding of the mRNA to the ribosome. Be the first codon, which is always a start codon methionine, filling the P site, and the second codon bias filling A bit point. , TRNA molecules, the anti-codon is complementary to the mRNA of the formation of a temporary base pair with the A site mRNA. A by a peptide bond is formed between the A bit, the methionine attached to the P sites in the amino acid the tRNA.

　　A site mRNA in the ribosome sliding down, so, tRNA in the A site for all mobile end to the P site, and a new codon fill the. Way (remember, this is one of the A site to bring the new amino acid to the growing polypeptide in the P site) and the appropriate aminoacyl tRNA carrying the appropriate amino acid of the acid paired with the base of this new codon in the A site. A peptide bond is formed between the held by the aminoacyl tRNA molecules formed into a first of the two chains of the chain buckle two adjacent amino acids.

　　The ribosomal again sliding. P sites, tRNA is let go into the cytoplasm, where it will eventually be carried out with another amino acid binding. Another aminoacyl tRNA relates to new codon binding in the A sites, and a peptide bond is formed between the amino acid to the growing peptide chain.

　　This process continues until three stop codons in one, into the A site. At this point, the protein chain. P sites in which it is connected to the tRNA is released. The translation is complete.

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