1. The nucleic acids, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), are polymers of nucleotide units 1.1 DNA consists of four kinds of deoxyribonucleotide units linked together through covalent bonds 1.1.1 Each nucleotide unit is made of a nitrogenous base (the various part in the four different deoxyribonucleotides), a pentose sugar and a phosphate group
1. Hemoglobin is a multisubunit allosteric rotein 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. 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
1. Carbohydrates are aldehyde or ketone compounds with multiple hydroxyl groups or substances that can yield such compounds on hydrolysis(p. 293) 1.1 Carbohydrates are the most abundant biomolecules on earth and have multiple roles in all forms of life. 1.1.1 Carbohydrates serve as energy stores (e.g., starch in plants, glycogen in animals), fuels (e.g., glucose), and metabolic intermediates (e.., ATP, many coenzymes)
1. The good and bad sides of using triacylglycerols as an energy storage Highly reduced, more than twice as much energy as carbohydrates or proteins (~38 kJ/g vs ~18 kJ/g). Highly hydrophobic: does not raise osmolarity of cytosol, nor add extra weight; but must be emulsified before digestion and transported by special proteins in blood
1. Reduction(fixation)of N, into ammonia(NH3 or NH*) 2. Synthesis of the 20 amino acids 3. Synthesis of other biomolecules from amino acids 4. The de novo pathways for purine and pyrimidinebiosynthesis 5. The salvage pathways for purine and pyrimidine reuse
Radioisotope tracer experiments showed that the porphyrin(卟啉) ring of the heme groups in mammals are made from 8 Gly and 8 succinyl-COA (Glu in plants and bacteria). Deficiency of enzymes leading to heme biosynthesis cause diseases called porphyrias (The degradation of heme yields bilirubin, a linear tetrapyrrole derivative, and the typical pigments found