1. Proteins are extremely versatile in function and crucial in virtually all biological processes. 1.1 Almost all chemical reactions occurring in living organisms are catalyzed by enzymes. 1.1.1 Many thousands of enzymes have been discovered, each catalyzing a different kind of chemical reaction
1. Lipids encompass a large and diverse group of organic compounds 1.1 Lipids are broadly defined as biological molecules that are soluble in organic solvents. 1.1.1 Lipids are usually extracted from biological materials by nonpolar solvents like ether, chloroform(氯仿), benzene(苯). 1.2 The biological functions of lipids are diverse. 1.2.1 Certain lipids(e.g., triacylglycerols(三脂酰甘油), commonly called fats) serve as efficient reserves for the storage of energy
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
