1.4.1 Amino acids are the building materials of proteins

R基：有极性和非极性之分，在水中非极性的会会因为疏水而折叠到结构内部，极性则相反

1.4.2 Peptide bonds link successive amino acids to form proteins

Peptide 二肽

The primary structure of a protein is its amino acids to form sequence

1.4.3 Proteins are folded into 3 dimensional shapes that determine their functions

Secondary structure: α - helix and β - pleated sheet (eg. spider web).

Tertiary structure (3rd structure): disulfide bridges(bonds) 二硫键+hydrogen bonds

Quaternary structure (4th structure): forms when 2+ polypeptides subunits interact to form a protein.

蛋白质四层结构：

1. 氨基酸 primary 共价键（肽键）连接
2. 氨基酸排列起来成的多肽链 secondary 氢键
3. 多肽链折叠形成的三维结构 tertiary 氢键，二硫键，离子键
4. 多条多肽链组合 quarternary

Denaturation 蛋白质变性