Biochemistry Seeks to Explain Life in Chemical Terms
The molecules of which living organisms are composed conform to all the familiar laws of chemistry, but they also
interact with each other in accordance with another set of principles, which we shall refer to collectively as the molecular
logic of life. These principles do not involve new or yet undiscovered physical laws or forces. Instead, they are a set of
relationships characterizing the nature, function, and interactions of biomolecules.
If living organisms are composed of molecules that are intrinsically inanimate, how do these molecules confer the
remarkable combination of characteristics we call life? How is it that a living organism appears to be more than the sum of
its inanimate parts? Philosophers once answered that living organisms are endowed with a mysterious and divine life force,
but this doctrine (vitalism) has been firmly rejected by modern science. The basic goal of the science of biochemistry is to
determine how the collections of inanimate molecules that constitute living organisms interact with each other to maintain
and perpetuate life. Although biochemistry yields important insights and practical applications in medicine, agriculture,
nutrition, and industry, it is ultimately concerned with the wonder of life itself.
All Macromolecules Are Constructed from a Few Simple Compounds
Most of the molecular constituents of living systems are composed of carbon atoms covalently joined with other carbon
atoms and with hydrogen, oxygen, or nitrogen. The special bonding properties of carbon permit the formation of a great
variety of molecules. Organic compounds of molecular weight less than about 500, such as amino acids, nucleotidase, and
monosaccharide, serve as monomeric subunits of proteins, nucleic acids, and
polysaccharides, respectively. A single protein
molecule may have 1,000 or more amino acids, and deoxyribonucleic acid has millions of nucleotides.
Each cell of the bacterium Escherichia coli (E. coli) contains more than 6,000 different kinds of organic compounds,
including about 3,000 different proteins and a similar number of different nucleic acid molecules. In humans there may be
tens of thousands of different kinds of proteins, as well as many types of polysaccharides (chains of simple sugars), a
variety of lipids, and many other compounds of lower molecular weight.
To purify and to characterize thoroughly all of these molecules would be an insuperable task, it were not for the fact
that each class of macromolecules (proteins, nucleic acids, polysaccharides) is composed of a small, common set of monomeric
subunits. These monomeric subunits can be covalently linked in a virtually limitless variety of sequences, just as the 26
letters of the English alphabet can be arranged into a limitless number of words, sentiments, or books.
Deoxyribonucleic acids (DNA) are constructed from only four different kinds of simple monomeric subunits, the
deoxyribonucleotides, and ribonucleic acids (RNA) are composed of just four types of ribonucleotides. Proteins are composed
of 20 different kinds of amino acids. The eight kinds of nucleotides from which all nucleic acids are built and the 20
different kinds of amino acids from which all proteins are built are identical in all living organisms.
Most of the monomeric subunits from which all macromolecules are constructed serve more than one function in living
cells. The nucleotides serve not only as subunits of nucleic acids, but also as energy-carrying molecules. The amino acids
are subunits of protein molecules, and also precursors of hormones, neurotransmitters, pigments, and many other kinds of
biomolecules.
From these considerations we can now set out some of the principles in the molecular logic of life: All living organisms
have the same kinds of monomeric subunits. There are underlying patterns in the structure of biological macromolecules. The
identity of each organism is preserved by its possession of distinctive sets of nucleic acids and of proteins.
ATP Is the Universal Carrier of Metabolic Energy, Linking Catabolism and Anabolism
Cells capture, store, and transport free energy in a chemical form. Adenosine triphosphate (ATP) functions as the major
carrier of chemical energy in all cells. ATP carries energy among metabolic pathways by serving as the shared intermediate
that couples endergonic reactions to exergonic ones. The terminal phosphate group of ATP is transferred to a variety of
acceptor molecules, which are thereby activated for further chemical transformation. The adenosine diphosphate (ADP) that
remains after the phosphate transfer is recycled to become ATP, at the expense of either chemical energy (during oxidative
phosphorylation) or solar energy in photosynthetic cells (by the process of photophosphorylation). ATP is the major
connecting link (the shared intermediate) between the catabolic and anabolic networks of enzyme-catalyzed reactions in the
cell. These linked networks of enzyme-catalyzed reactions are virtually identical in all living organisms.
Genetic Continuity Is Vested in DNA Molecules
Perhaps the most remarkable of all the properties of living cells and organisms is their ability to reproduce themselves
with nearly perfect fidelity for countless generations. This continuity of inherited traits implies constancy, over thousands
or millions of years, in the structure of the molecules that contain the genetic information. Very few historical records of
civilization, even those etched in copper or carved in stone, have survived for a thousand years. But there is good evidence
that the genetic instructions in living organisms have remained nearly unchanged over much longer periods; many bacteria have
nearly the same size, shape, and internal structure and contain the same kinds of precursor molecules and enzymes as those
that lived a billion years ago.
Hereditary information is preserved in DNA, a long, thin organic polymer so fragile that it will fragment from the shear
forces arising in a solution that is stirred or pipetted. A human sperm or egg, carrying the accumulated hereditary
information of millions of years of evolution, transmits these instructions in the form of DNA molecules, in which the linear
sequence of covalently linked nucleotide subunits encodes the genetic message. Genetic information is encoded in the linear
sequence of four kinds of subunits of DNA. The double-helical DNA molecule has an internal template for its own replication
and repair.
The Structure of DNA Allows for Its Repair and Replication with Near-Perfect Fidelity
The capacity of living cells to preserve their genetic material and to duplicate it for the next generation results from
the structural complementarity between the two halves of the DNA molecule. The basic unit of DNA is a linear polymer of four
different monomeric subunits, deoxyribonucleotides, arranged in a precise linear sequence. It is this linear sequence that
encodes the genetic information. Two of these polymeric strands are twisted about each other to form the DNA double helix,
in which each monomeric subunit in one strand pairs specifically with the complementary subunit in the opposite strand. In
the enzymatic replication or repair of DNA, one of the two strands serves as a template for the assembly of another,
structurally complementary DNA strand. Before a cell divides, the two DNA strands separate and each serves as a template for
the synthesis of a complementary strand, generating two identical double-helical molecules, one for each daughter cell. If
one strand is damaged, continuity of information is assured by the information present on the other strand.
The Linear Sequence in DNA Encodes Proteins with Three-Dimensional Structures
The information in DNA is encoded as a linear (one-dimensional) sequence of the nucleotide units of DNA, but the
expression of this information results in a three-dimensional cell. This change from one to three dimensions occurs in two
phases. A linear sequence of deoxyribonucleotides in DNA codes (through the intermediary, RNA) for the production of a
protein with a corresponding linear sequence of amino acids. The protein folds itself into a particular three-dimensional
shape, dictated by its amino acid sequence. The precise three-dimensional structure (native conformation) is crucial to the
protein’s function as either catalyst or structural element. This principle emerges:
The linear sequence of amino acids in a protein leads to the acquisition of a unique three-dimensional structure by a
self-assembly procession.
Once a protein has folded into its native conformation, it may associate noncovalently with other proteins, or with
nucleic acids or lipids, to form supramolecular complexes such as chromosomes, ribosomes, and membranes. These complexes are
in many cases self-assembling. The individual molecules of these complexes have specific, high-affinity binding sites for
each other, and within the cell they spontaneously form functional complexes.
Individual macromolecules with specific affinity for other macromolecules self-assemble into supramolecular complexes.
Noncovalent Interactions Stabilize Three-Dimensional Structures
The forces that provide stability and specificity to the three-dimensional structures of macromolecules and
supramolecular complexes are mostly noncovalent interactions. These interactions, individually weak but collectively strong,
include hydrogen bonds, ionic interactions among charged groups, van der Waals interactions, and hydrophobic interactions
among nonpolar groups. These weak interactions are transient; individually they form and break in small fractions of a second.
The transient nature of noncovalent interactions confers a flexibility on macromolecules that is critical to their function.
Furthermore, the large numbers of noncovalent interactions in a single macromolecule makes it unlikely that at any given
moment all the interactions will be broken; thus macromolecular structures are stable over time.
Three-dimensional biological structures combine the properties of flexibility and stability.
The flexibility and stability of the double-helical structure of DNA are due to the complementarity of its two strands
and many weak interactions between them. The flexibility of these interactions allows strand separation during DNA
replication; the complementarity of the double helix is essential to genetic continuity.
Noncovalent interactions are also central to the specificity and catalytic efficiency of enzymes. Enzymes bind
transition-state intermediates through numerous weak but precisely oriented interactions. Because the weak interactions are
flexible, the complex survives the structural distortions as the reactant is converted into product.
The formation of noncovalent interactions provides the energy for self-assembly of macromolecules by stabilizing native
conformations relative to unfolded, random forms. The native conformation of a protein is that in which the energetic
advantages of forming weak interactions counterbalance the tendency of the protein chain to assume random forms. Given a
specific linear sequence of amino acids and a specific set of conditions (temperature, ionic conditions, pH), a protein will
assume its native conformation spontaneously, without a template or scaffold to direct the folding.
The Physical Roots of the Biochemical World
We can now summarize the various principles of the molecular logic of life:
A living cell is a self-contained, self-assembling, self-adjusting, self-perpetuating isothermal system of molecules that
extracts free energy and raw materials from its environment.
The cell carries out many consecutive reactions promoted by specific catalysts, called enzymes, which it produces itself.
The cell maintains itself in a dynamic steady state, far from equilibrium with its surroundings. There is great economy
of parts and processes, achieved by regulation of the catalytic activity of key enzymes.
Self-replication through many generations is ensured by the self-repairing, linear information-coding system. Genetic
information encoded as sequences of nucleotide subunits in DNA and RNA specifies
the sequence of amine acids in each distinct
protein, which ultimately determines the three-dimensional structure and function of each protein.
Many weak (noncovalent) interactions, acting cooperatively, stabilize the three-dimensional structures of biomolecules
and supramolecular complexes.
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Biochemistry Seeks to Explain Life in Chemical Terms The molecules of which living organisms are composed conform to all the familiar laws of chemistry, but they also interact with each other in accordance with another set of principles, which we shall refer to collectively as the molecular logic of life. These principles do not involve new or yet undiscovered physical laws or forces. Instead, they are a set of relationships characterizing the nature, function, and interactions of biomolecules. If living organisms are composed of molecules that are intrinsically inanimate, how do these molecules confer the remarkable combination of characteristics we call life? How is it that a living organism appears to be more than the sum of its inanimate parts? Philosophers once answered that living organisms are endowed with a mysterious and divine life force, but this doctrine (vitalism) has been firmly rejected by modern science. The basic goal of the science of biochemistry is to determine how the collections of inanimate molecules that constitute living organisms interact with each other to maintain and perpetuate life. Although biochemistry yields important insights and practical applications in medicine, agriculture, nutrition, and industry, it is ultimately concerned with the wonder of life itself. All Macromolecules Are Constructed from a Few Simple Compounds Most of the molecular constituents of living systems are composed of carbon atoms covalently joined with other carbon atoms and with hydrogen, oxygen, or nitrogen. The special bonding properties of carbon permit the formation of a great variety of molecules. Organic compounds of molecular weight less than about 500, such as amino acids, nucleotidase, and monosaccharide, serve as monomeric subunits of proteins, nucleic acids, and polysaccharides,
Introduction to Physiology Introduction Physiology is the study of the functions of living matter. It is concerned with how an organism performs its varied activities: how it feeds, how it moves, how it adapts to changing circumstances, how it spawns new generations. The subject is vast and embraces the whole of life. The success of physiology in explaining how organisms perform their daily tasks is based on the notion that they are intricate and exquisite machines whose operation is governed by the laws of physics and chemistry. Although some processes are similar across the whole spectrum of biology—the replication of the genetic code for or example—many are specific to particular groups of organisms. For this reason it is necessary to divide the subject into various parts such as bacterial physiology, plant physiology, and animal physiology. To study how an animal works it is first necessary to know how it is built. A full appreciation of the physiology of an organism must therefore be based on a sound knowledge of its anatomy. Experiments can then be carried out to establish how particular parts perform their functions. Although there have been many important physiological investigations on human volunteers, the need for precise control over the experimental conditions has meant that much of our present physiological knowledge has been derived from studies on other animals such as frogs, rabbits, cats, and dogs. When it is clear that a specific physiological process has a common basis in a wide variety of animal species, it is reasonable to assume that the same principles will apply to humans. The knowledge gained from this approach has given us a great insight into human physiology and endowed us with a solid foundation for the effective treatment of many diseases. The building blocks of the body are the cells, which are grouped together to form tissues. The principal types of tissue are epithelial, connective, nervous, and muscular, each with its own characteristics. Many connective tissues have relatively few cells but have an extensive extracellular matrix. In contrast, smooth muscle consists of densely packed layers of muscle cells linked together via specific cell junctions. Organs such as the brain, the heart, the lungs, the intestines, and the liver are formed by the aggregation of different kinds of tissues. The organs are themselves parts of distinct physiological systems. The heart and blood vessels form the cardiovascular system; the lungs, trachea, and bronchi together with the chest wall and diaphragm form the respiratory system; the skeleton and skeletal muscles form the musculoskeletal system; the brain, spinal cord, autonomic nerves and ganglia, and peripheral somatic nerves form the nervous system, and so on. Cells differ widely in form and function but they all have certain 生理学简介 介绍 生理学是研究生物体功能的科学。它研究生物体如何进行各种活动，如何饮食，如何运动，如何适应不断改变的环境，如何繁殖后代。这门学科包罗万象，涵盖了生物体整个生命过程。生理学成功地解释了生物体如何进行日常活动，基于的观点是生物体好比是结构复杂而灵巧的机器，其操作受物理和化学规律控制。 尽管从生物学整个范畴看，生物体某些活动过程是相似的——如基因编码的复制——但许多过程还是某些生物体群组特有的。鉴于此有必要将这门学科分成不同部分研究，如细菌生理学、植物生理学和动物生理学。 要研究一种动物如何活动，首先需要了解它的构成。要充分了解一个生物体的生理学活动就必须掌握全面的解剖学知识。一个生物体的各部分起着什么作用可通过实验观察得知。尽管我们对志愿者进行了许多重要的生理调查，但是实验条件需要精确控制，所以我们当前大多生理知识还是源于对其它动物如青蛙，兔子，猫和狗等的研究。当我们明确大多数动物物种的特定生理过程存在共同之处时，相同的生理原理适用于人类也是合理的。通过这种方法，我们获得了大量的知识，从而让我们对人类生理学有了更深入的了解，为我们有效治疗许多疾病提供了一个坚实的基础。 机体的基本组成物质是细胞，细胞结合在一起形成组织。组织的基本类型有上皮组织，结缔组织，神经组织和肌组织，每类组织都有各自的特征。许多结缔组织中细胞量相对较少，但是有大量的细胞外基质。相比而言，光滑的肌组织由大量密密麻麻的肌细胞通过特定的细胞连接组成。各种器官如脑，心脏，肺，小肠和肝等由不同种类的组织聚集而成。这些器官是不同生理系统的组成部分。心脏和血管组成心血管系统；肺，器官，支气管，胸壁和膈肌组成呼吸系统；骨骼和骨骼肌组成骨骼肌系统；大脑，脊髓，自主神经和神经中枢以及
IntroductiontoPhysiology Introduction Physiologyisthestudyofthefunctionsoflivingmatter.Itisconcernedwithhowanorganismperformsitsv ariedactivities:howitfeeds,howitmoves,howitadaptstochangingcircumstances,howitspawnsnewgenerati ons.Thesubjectisvastandembracesthewholeoflife.Thesuccessofphysiologyinexplaininghoworganismsp erformtheirdailytasksisbasedonthenotionthattheyareintricateandexquisitemachineswhoseoperationisgo vernedbythelawsofphysicsandchemistry. Althoughsomeprocessesaresimilaracrossthewholespectrumofbiology—thereplicationofthegenetic codefororexample—manyarespecifictoparticulargroupsoforganisms.Forthisreasonitisnecessarytodivid ethesubjectintovariouspartssuchasbacterialphysiology,plantphysiology,andanimalphysiology. Tostudyhowananimalworksitisfirstnecessarytoknowhowitisbuilt.Afullappreciationofthephysiolog yofanorganismmustthereforebebasedonasoundknowledgeofitsanatomy.Experimentscanthenbecarriedo uttoestablishhowparticularpartsperformtheirfunctions.Althoughtherehavebeenmanyimportantphysiolo gicalinvestigationsonhumanvolunteers,theneedforprecisecontrolovertheexperimentalconditionshasmea ntthatmuchofourpresentphysiologicalknowledgehasbeenderivedfromstudiesonotheranimalssuchasfrog s,rabbits,cats,anddogs.Whenitisclearthataspecificphysiologicalprocesshasacommonbasisinawidevariet yofanimalspecies,itisreasonabletoassumethatthesameprincipleswillapplytohumans.Theknowledgegain edfromthisapproachhasgivenusagreatinsightintohumanphysiologyandendoweduswithasolidfoundation fortheeffectivetreatmentofmanydiseases. Thebuildingblocksofthebodyarethecells,whicharegroupedtogethertoformtissues.Theprincipaltype softissueareepithelial,connective,nervous,andmuscular,eachwithitsowncharacteristics.Manyconnective tissueshaverelativelyfewcellsbuthaveanextensiveextracellularmatrix.Incontrast,smoothmuscleconsists https://www.doczj.com/doc/fb17040192.html,anssuchasthebrain,theh eart,thelungs,theintestines,andtheliverareformedbytheaggregationofdifferentkindsoftissues.Theorgans arethemselvespartsofdistinctphysiologicalsystems.Theheartandbloodvesselsformthecardiovascularsyst em;thelungs,trachea,andbronchitogetherwiththechestwallanddiaphragmformtherespiratorysystem;thes keletonandskeletalmusclesformthemusculoskeletalsystem;thebrain,spinalcord,autonomicnervesandgan glia,andperipheralsomaticnervesformthenervoussystem,andsoon. Cellsdifferwidelyinformandfunctionbuttheyallhavecertaincommoncharacteristics.Firstly,theyareb oundedbyalimitingmembrane,theplasmamembrane.Secondly,theyhavetheabilitytobreakdownlargemol eculestosmalleronestoliberateenergyfortheiractivities.Thirdly,atsomepointintheirlifehistory,theyposses sanucleuswhichcontainsgeneticinformationintheformofdeoxyribonucleicacid(DNA). Livingcellscontinuallytransformmaterials.Theybreakdownglucoseandfatstoprovideenergyforother activitiessuchasmotilityandthesynthesisofproteinsforgrowthandrepair.Thesechemicalchangesarecollect ivelycalledmetabolism.Thebreakdownoflargemoleculestosmalleronesiscalledcatabolismandthesynthes isoflargemoleculesfromsmalleronesanabolism. Inthecourseofevolution,cellsbegantodifferentiatetoservedifferentfunctions.Somedevelopedtheabil itytocontract(musclecells),otherstoconductelectricalsignals(nervecells).Afurthergroupdevelopedtheabi litytosecretedifferentsubstancessuchashormonesorenzymes.Duringembryologicaldevelopment,thispro cessofdifferentiationisre-enactedasmanydifferenttypesofcellareformedfromthefertilizedegg. Mosttissuescontainamixtureofcelltypes.Forexample,bloodconsistsofredcells,whitecells,andplatele ts.Redcellstransportoxygenaroundthebody.Thewhitecellsplayanimportantroleindefenseagainstinfection 生理学简介 介绍 生理学是研究生物体功能的科学。它研究生物体如何进行各种活动，如何饮食，如何运动，如何适应不断改变的环境，如何繁殖后代。这门学科包罗万象，涵盖了生物体整个生命过程。生理学成功地
Drug Discovery and Natural Products It may be argued that drug discovery is a recent concept that evolved from modern science during the 20th century, but this concept in reality dates back many centuries, and has its origins in nature. On many occasions, humans have turned to Mother Nature for cures, and discovered unique drug molecules. Thus, the term natural product has become almost synonymous with the concept of drug discovery. In modem drug discovery and development processes, natural products play an important role at the early stage of "lead" discovery, i.e. discovery of the active (determined by various bioassays) natural molecule, which itself or its structural analogues could be an ideal drug candidate. 1.origin ['?rid?in] n.起点，端点; 来源；出身, 血统. 2.Synonymous [s?'n?n?m?s]adj.同义的，类义的. 3.i.e. [,a?'i:] <拉> abbr. (=id est) 即，换言之. 4.candidate ['k?ndidit] n.申请求职者, 候选人；报考者；候选物. 有人可能认为药物发现是一个20世纪才出现的、来源于现代科学的新概念，但是事实上这个概念是源于自然界的，可以追溯到许多个世纪以前。过去，人们常常向自然母亲寻求帮助，并且找到了分子结构独特的药物。在那时，天然产物几乎是药物发现的同义词。天然产物在现代药物发现和开发过程中也发挥着重要的作用，即作为天然活性化合物（通过各种生物检定方法）的来源，而天然活性化合物或者其结构类似物可能是很好的候选药物。 Natural products have been enormous source of drugs and drug leads. It is estimated that 61 percent of the 877 small-molecular new chemical entities introduced as drugs worldwide during 1981-2002 can be traced back to or were developed from natural products. These include natural products (6 percent), natural product derivatives (27 percent), and synthetic compounds with natural-product-derived pharmacophores (5 percent) and synthetic compounds designed on the basis of knowledge gained from a natural product, i.e. a natural product mimic (23 percent). In some therapeutic areas, the contribution of natural products is even greater, e.g. about 78 percent of antibacterials and 74 percent of anticancer drug candidates are natural products or structural analogues of natural products. In 2000, approximately 60 percent of all drugs in clinical trials for the multiplicity of cancers were of natural origins. In 2001, eight (simvastatin, pravastatin, amoxycillin, clavulanic acid,
Unit 1 1. A full appreciation of the physiology of a living organism must be based on a sound knowledge of its anatomy. Anatomy does not merely study the separation of parts, but the accurate description of the morphologie s and functions of different organs. 对生物生理学的全面了解必须基于解剖学的系统知识。解剖学不仅仅是研究人体各部分的分离，还要准确的描述各个器官的形态和生理功能。 2.Our daily food intake must match requirements and any excess must be excreted for balance to be maintained. 我们每天摄入的事物必须满足需要，任何多余的东西必须排出体外才能维持平衡。 3.The process of stabilization of the internal environment is called homeostasis and is essential if the cells of the body are to function normally. 内环境稳定的过程称之为体内平衡，体内平衡也是机体的细胞正常发挥作用所必不可少的。 4.Human cells have the ability to break down large molecules to smaller ones to liberate sufficient energy for their activities. 人类细胞有将大分子分解成小分子的能力，从而为自身活动释放足够的能量。 5.As long as normal conditions are maintained in this internal environment, the cells of the body continue to live and function properly. 只要这种内环境正常的条件得以维持，机体的细胞就能继续生存并发挥正常功能。 Unit 2 1.Biochemistry asks how the thousands of different biomolecules interact with each other to confer the remarkable properties of living organisms. 生物化学探寻的是数千种不同的生物分子如何相互作用，以赋予生物体具备显著的特性。 2.Enzymes are catalysts that accelerate the rates of biological reactions. Each enzyme is very specific in its function and acts only in a particular metabolic reaction. 酶是能加速生物学反应速率的催化剂。每一种酶都有专一的功能并且仅在特定代谢反应中发挥作用。 3.One of the most fruitful approaches to understand biological phenomena has been to purify an individual chemical component, such as a protein, from a living organism and to characterize its chemical structure or catalytic activity. 用以了解生物学现象的最有效的方法之一是从生物体中纯化出单一化学成分，例如蛋白质，并对其化学结构或催化活性进行表征。 4.The chemical principles that govern the properties of biological molecules include the covalent bonding of carbon with itself and with other elements and the functional groups that appear in common biological molecules, etc. 决定生物分子特性的化学原理包括碳与自身或其他元素的共价结合和一般生物分子中出现的功能基团等。 5.The basic unit of DNA is a linear polymer of four different monomeric subunits, deoxyribonucleotides, arranged in a precise linear sequence. 脱氧核糖核酸的基本单位是由四种不同的脱氧核糖核苷酸单一亚单位以精确的线性序列进行排列而构成的线性聚合物。 Unit 3 1.Although the existence of microbes was determined almost three hundred years ago, the study of microbiology is only getting started compared with zoology and
LESSON FIVE Chemistry and Matter Why study chemistry? An important reason is indicated in the foregoing statement by Benjamin Franklin—it is through chemistry and her sister sciences that the power of man, of mind, over matter is obtained. Nearly two hundred years ago Franklin said that science was making rapid progress. We know that the rate of progress of science has become continually greater, until now the world in which we live has been greatly changed, through scientific and technical progress, from t hat of Frank1in’s time. Science plays such an important part in the modern world that no one can now feel that he understands the world in which he lives unless he has an understanding of science. The science of chemistry deals with substances. At this point in the study of chemistry we shall not define the word substance in its scientific sense, but shall, assume that you have a general idea of what the word means. Common examples of substances are water, sugar, salt, copper, iron, oxygen-you can think of many others. A century and a half ago it was discovered by an English chemist, Sir Humphry Davy, that common salt can be separated, by passing electricity through it, into a soft, silvery metal, to which he gave the named sodium, and a greenish-yellow gas, which had been discovered some time earlier, named chlorine. Chlorine is a corrosive gas, which attacks many metals, and irritates the mucous membranes of the nose and throat if it is inhaled. That the substance salt is composed of a metal (sodium) and a corrosive gas (chlorine) with properties quite different from its own properties is one of the many surprising facts about the nature of substances that chemists have discovered. A sodium wire will burn in chlorine, producing salt/. The process of combination of sodium and chlorine to form salt is called a chemical reaction. Ordinary fire also involves a chemical reaction, the combination of the fuel with oxygen in the air to form the products of combustion. For example, gasoline contains compounds of carbon and hydrogen, and when a mixture of gasoline and air burns rapidly in the cylinders of an automobile a chemical reaction takes place, in which the gasoline and the oxygen of the air react to form carbon dioxide and water vapor (plus a small amount of carbon monoxide), and at the same time to release the energy that moves the automobile. Carbon dioxide and carbon monoxide are compounds of carbon and oxygen, and water is a compound of hydrogen and oxygen. Chemists study substances in order to learn as much as they can about their properties (their characteristic qualities) and about the react ions that change them into other substances. Knowledge obtained in this way has been found to be extremely valuable. It not only satisfies man’s curiosity about himself and about the world in which he lives, but it also can be applied to make the world a better place to live in, to make people happier by raising their standards of 1ivng, ameliorating the suffering due to ill health, and enlarging the sphere of their activities. Let us consider some of the ways in which knowledge of chemistry has helped man in the past and may help him in the future. It was discovered centuries ago that preparations could be made from certain plants, such as poppies and coca, which, when taken by a human being, serve to deaden pain (are analgesics). From these plants chemists isolated pure substances, morphine and cocaine, which have the pain deadening property. These substances have, however, an undesirable property, that of
一、熟悉下列句子的翻译 1. In addition to the revolution in new classes of drugs, an equally momentous revolution is taking place in drug delivery. 除药物种类的革命外，药物给药系统也在进行一场同样令人震撼的革命。 2. The body can make about a trillion different antibodies, produced by shuffling and reshuffling their constituent parts. 通过对构成成分的改组和再改组，机体可以产生约一万亿个不同的抗体。 3. Under current law, all new drugs need proof that they are effective, as well as safe, before they can be approved for marketing. 现有法律要求，所有的新药都必须具有其有效、安全的证据才能被批准上市。 4．There is no agreement whether nursing mothers could use Alexan. 哺乳期妇女是否能用爱力生尚无统一意见。 5. The prescription must be signed and dated by the practitioner and include his address. 处方必须由医生亲笔签名，并注明日期和医生的地址。 6. Cells possess a nucleus which contains genetic information in the form of DNA. 细胞含有一个细胞核，其中含有以脱氧核糖核酸（DNA）形式表达的基因信息。 7. A drug that is not covered by patent rights may be available in several proprietary formulations of the same generic preparation. 没有专利权保护的药物可以用于同一个仿制剂型的多个专利配方中。 8. When a drug is used by millions, there are certain to be adverse reactions even though the risk to any individual is small. 当某种药物被数百万人使用时，肯定会有不良反应出现，尽管具体到个人，这种危险性并不大。 9. The end point is also called equivalent point, since the titrant and tested sample are chemically equivalent. 滴定终点也称为等当点，因为测定剂和被测样本在化学量上是相等的。10. It is estimated that less than 30% of the hypertensive patients have their blood pressure adequately controlled. 据估计，只有不到30%的患者的高血压得到了适当的控制。 11. Based on the data collected, numerous valuable compounds can be determined without reference to specimens of that same compound.