The primary structure of 1, concept: In protein molecule, the arrangement order of amino acid residues from N-terminal to C-terminal is called the primary structure of protein. Features: (1) There are many kinds of protein, and their primary mechanisms are also different; (2) The primary structure is the basis of protein's spatial conformation and specific biological functions. (3) The primary structure is not the only factor that determines the spatial conformation of protein. Chemical bond: (1) peptide bond (2) disulfide bond.

2 protein secondary structure: Concept: refers to the local spatial structure of a peptide chain in protein molecule, that is, the relative spatial position of skeleton atoms in the main chain of the peptide chain, and does not involve the conformation of the side chain of amino acid residues.

Features: (1) is a local structure. (2) It is only a spatial structure formed by the interaction between peptide units, but it does not include the conformation formed by amino acid side chains and their A-A-F -H principle, but the side chains of amino acid residues have an influence on the formation of secondary structures. (3) There are many types of secondary structures, including A-helix, B-fold, B-corner and random curl. Among them, a- helix and B- folding are the main forms of secondary structure, and B- corner is usually composed of four amino acid residues, while random curl refers to some secondary structures with uncertain regularity or no regularity at all; (4) The secondary structure may also become super secondary structure, such as aa type, BaB type and BBB type. Chemical bond: hydrogen bond.

3 The tertiary structure of protein: concept: refers to the relative spatial position of all amino acid residues in the whole peptide chain, that is, the arrangement position of all atoms in the whole peptide chain in three-dimensional space. Characteristics: Three-dimensional spatial structure of polypeptide chain. Chemical bond: (1) hydrophobic bond (2) salt bond (3) hydrogen bond (4) Van der Waals force.

Protein quaternary structure: Concept: The spatial arrangement of subunits in protein molecule and the layout and interaction of the contacting parts of subunits are called protein quaternary structure. Features: Three-dimensional conformation formed by two or more polypeptide chains. Chemical bond: (1) hydrophobic bond (2) salt bond (3) hydrogen bond (4) Van der Waals force.