A-Level的生物复习笔记第三弹，今天小编继续就给大家分享一下复习干活！
Part 3 ：Protein synthesis
■ Two strands of DNA: sense strand (coding strand) + antisense strand (template strand)
■ The genes are on the antisense strand
■ Transcription (occurs in the nucleus):
1. Double strands of DNA are unwound and unzipped and the antisense strand is used as the template.
2. RNA nucleotides pair up with their complementary bases on the template strand via hydrogen bonds.
3. RNA polymerase catalyse the formation of the phosphodiester bonds between the RNA nucleotides.
4. The mRNA molecules is formed, and then the hydrogen bonds between the mRNA and DNA template strand are broken.
5. The DNA rewind into the double helix structure and mRNA molecule leaves the nucleus via nuclear pore.
■ Translation: (occurs on the ribosome)：
1. The mRNA moves into the cytoplasm and attached by ribosomes to provide the binding site for tRNA.
2. tRNA will brings the specific amino acids and bind with the mRNA and ribosome via the complementary base pairing between the codon and anticodon.
3. Then, second tRNA bring another amino acids and bind with the mRNA.
4. The peptide bond form between the adjacent amino acids.
5. The first tRNA detached from the its amino acids and he ribosome moves along the mRNA molecule, and a new tRNA with the amino acids will bind with the next codon.
6. The polypeptide is formed gradually until the ribosome reach the stop codon, then the formation of the polypeptide is completely. It will fold in the secondary and tertiary structure immediately.
7. The mRNA can be read by several ribosomes at the same time to produce many polypeptide.
整理了这么多，希望能够在考试中帮到大家，如果同学们对A-level的学习还有什么疑问，欢迎随时联系我们哦~
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