The joining of the amino acids into a chain results in the formation of a polypeptide chain which then folds into the compact, globular three-dimensional structure that is a functional protein.
氨基酸连接起来形成多肽链，多肽链又折叠压缩成球状三维结构的功能蛋白。
2
This spatial configuration of the polypeptide chain is the secondary structure.
肽链的这个空间构象就是二级结构。
3
The structure of many proteins is mostly described in three levels, but a quaternary structural level must be considered if the protein consists of more than one polypeptide chain.