生化题（Biochemical problems）.docVIP

生化题（Biochemical problems） I. what are the one or two and three or four structures of proteins and what are the keys or forces that maintain the structure of all levels? Answer: the composition and sequence of amino acid residues in the polypeptide chain is called the primary structure, secondary structure is connected with a peptide bond. The two structure refers to the local space structure of the protein backbone atoms, and does not involve the conformation of amino acid residues. The species include a- helix, b- fold, b- corner, and random crimp. Hydrogen bonds are the major bonds. The three structure refers to the space arrangement of the polypeptide chain and the side chain atom. The secondary key to maintain its stability, the main key is hydrophobic. A four - stage structure is the association of two or more polypeptide chains with three - stage structures. Each polypeptide chain having a three structure is called a subunit, and a protein with a four order structure is biologically active. To maintain its stability is a secondary key, such as hydrogen bond and hydrophobic force van Edward salt Two, the main points of DNA double helix structure are briefly described Answer: 1.DNA is a antiparallel, double stranded structure with the backbone of the ribose and phosphoric acid located on the outside of the double chain, the base located on the inside, and the bases between the two chains bonded to hydrogen bonds. Adenine is always paired with thymine, forming two hydrogen bonds (A=T), and guanine is always paired with cytosine to form three hydrogen bonds (G=C). The base plane is perpendicular to the long axis of the linear molecular structure. The direction of a chain is 5-3, and the other chain must be 3-5. 2.DNA is a right-handed spiral structure. Each rotation of the helix contains ten pairs of bases, the rotation angle of the base is 36 degrees, the pitch is 3.4nm, and the distance between each base plane is 0.34nm. DNA double helix. There is a big and a sm