翻译英文生物课本

专业词汇要求精确翻译，语句专业流畅The word protein that I propose to you . . . I would wish toderive from proteios, because it appears to be theprimitive or principal substance of animal nutrition thatplants prepare for the herbivores, and which the latterthen furnish to the carnivores.—J. J. Berzelius, letter to G. J. Mulder, 1838Proteins are the most abundant biological macromolecules,occurring in all cells and all parts of cells. Proteinsalso occur in great variety; thousands of differentkinds, ranging in size from relatively small peptides tohuge polymers with molecular weights in the millions,may be found in a single cell. Moreover, proteins exhibitenormous diversity of biological function and are themost important final products of the information pathwaysdiscussed in Part III of this book. Proteins are themolecular instruments through which genetic informationis expressed.Relatively simple monomeric subunits provide thekey to the structure of the thousands of different proteins.All proteins, whether from the most ancient linesof bacteria or from the most complex forms of life, areconstructed from the same ubiquitous set of 20 aminoacids, covalently linked in characteristic linear sequences.Because each of these amino acids has a side chain withdistinctive chemical properties, this group of 20 precursormolecules may be regarded as the alphabet inwhich the language of protein structure is written.What is most remarkable is that cells can produceproteins with strikingly different properties and activitiesby joining the same 20 amino acids in many differentcombinations and sequences. From these buildingblocks different organisms can make such widely diverseproducts as enzymes, hormones, antibodies, transporters,muscle fibers, the lens protein of the eye, feathers,spider webs, rhinoceros horn, milk proteins, antibiotics,mushroom poisons, and myriad other substanceshaving distinct biological activities (Fig. 3–1). Amongthese protein products, the enzymes are the most variedand specialized. Virtually all cellular reactions arecatalyzed by enzymes.Protein structure and function are the topics of thisand the next three chapters. We begin with a descriptionof the fundamental chemical properties of aminoacids, peptides, and proteins.3.1 Amino AcidsProtein Architecture—Amino AcidsProteins are polymers of amino acids, with each aminoacid residue joined to its neighbor by a specific typeof covalent bond. (The term “residue” reflects the lossof the elements of water when one amino acid is joinedto another.) Proteins can be broken down (hydrolyzed)to their constituent amino acids by a variety of methods,and the earliest studies of proteins naturally focused on