Section M Nitrogen Metabolism M1. Nitrogen Fixation and Assimilation M2. Amino acid metabolism M3. The urea cycle M4. Hemes and chlorophylls

Section L Respiration and Energy L1. Citric acid cycle L2. Electron transport and oxidative hosphory lation L3. Photosynthesis

Section K Lipid metabolism K1. Structures and roles of fatty acids K2 Fatty acid breakdown K3. Fatty acid synthesis K4 Metabolism of triacylglycerols K5. Cholesterol metabolism K6 Lipoproteins

一,喙头蜥目 二,龟鳖目 三,蜥蜴目 四,蛇目

1. Hemoglobin is a multisubunit allosteric protein that carries 02 in erythrocyte. 1.1 Hemoglobin is a well-studied and well-understood protein. 1.1.1 It was one of the first proteins to have its molecular mass accurately determined. 1.1.2 The first protein to be characterized by ultracentrifuge. 1.1.3 The first protein to be associated with a specific physiological function

1. General studies of the peptide bond 1.1 The peptide(O=C-N-H) bond was found to be shorter than the C-N bond in a simple amine and atoms attached are coplanar. 1.1.1 This was revealed by X-ray diffraction studies of amino acids and of simple dipeptides and tripeptides. 1.1.2 The peptide (amide) bond was found to be about 1.32 A (C-N single bond, 1.49; C= double bond, 1.27), thus having partial double bond feature (should be rigid and unable to rotate freely)

Chapter Amino Acids, Peptides, and Proteins 0. General Introduction Proteins are polymers(多聚体) of amino acids. -20 amino acids(氨基酸)→ millions of proteins with different properties and activities. Protein structures are studied at primary, secondary, tertiary and quaternary levels. -a helix, B sheets, globular, complexes, denaturation and folding. Proteins have widely diverse forms and functions

1. Enzymes were among the first biological macromolecules to be studied chemically 1.1 Much of the early history of biochemistry is the history of enzyme research. 1.1.1 Biological catalysts were first recognized in studying animal food digestion and sugar fermentation with yeast (brewing and wine making)

1. Early studies on the peptide(protein) structure 1.1 The peptide(o=c-n-h) bond was found to be shorter than the C-N bond in a simple amine and atoms attached are coplanar. 1.1.1 This was revealed by X-ray diffraction studies of amino acids and of simple dipeptides and tripeptides

Assay:化验,分析,测定。 Enzyme activity: unit() is defined as the amount of enzyme which convert 1 micromole (umol) of substrate to product(s) in 1 minute under specified conditions. Specific activity: enzyme activity expressed per unit mass of protein present. (units/mg)