生物化学ProteinsynthesisPPT课件.ppt
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1、Proteinsynthesis,Chapter 13,translation,The nucleotide sequence of mRNA is translated into a sequence of amino acids by a genetic code(遗传密码) from its 5 end to 3 end.,what the translation needs,mRNA (template) amino acids (materials) ribosome (factory, rRNA and protein) ATP and GTP (energy) tRNA (car
2、rier, interpreter),13.1 The genetic code,The genetic code is the rules that specify how the nucleotide sequence of an mRNA is translated into the amino acid sequence of a polypeptide. The nucleotide sequence is read as triplet codon (三联子密码).,遗传密码,mRNA 分子中所储存的遗传信息是由其分子的四种碱基以特定顺序排列成的三个一组的三联体代表的,每种氨基酸都
3、有其特定的三联体密码。,That means three nucleotides produce one amino acid(43).,Features of genetic code,the genetic code is universal.(通用性) it is almost the same in all organisms. the genetic code is unambiguous.(不重复) each codon corresponds to only one amino acid.,the genetic code is degenerate(简并). in most c
4、ases, one amino acid is coded by several codons, which are called synonymous codons(同义密码子). the genetic code is wobbling(摆动) each codon is recognized by a triplet of bases, called an anticodon(反义密码子) in RNA. Each codon base pairs with its complementary anticodon base. However, the pairing of the thi
5、rd base of a codon is less stringent than for the first two bases.,13.2 Transfer RNA,the secondary structure of tRNA is cloverleaf(三叶草形). It contains five arms: acceptor stem(受体臂), D arm(双氢尿嘧啶臂), TC arm(假尿嘧啶臂), anticodon arm and extra arm.,the tertiary structure of tRNA is an inverse “L” form.,The f
6、unction of tRNA,Each tRNA becomes covalently bonded to a specific amino acid to form aminoacyl-tRNA (氨酰tRNA) which recognizes the corresponding codon in mRNA and ensures that the correct amino acid is added to the growing polypeptide chain.,13.3 Ribosomes,Ribosomes are large ribonucleoprotein(核蛋白) p
7、articles that contain more RNA than protein and dissociate into large and small subunits.,13.4 Process of translation,During translation the mRNA is read from 5 end to 3 end, and protein is synthesized in an N terminal to C terminal direction.,Principle for DNA replication: base-pairing Principle fo
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