(BIOLOGY)(英文原文及翻译) (biology的形容词)
(BIOLOGY)(英文原文及翻译) (biology的形容词)
CHAPTER1 第一章
The science of biology 生物学
(第一章内容较为简单，暂不做细述)
1-1The science of life 生命科学
1-2The nature of science 科学的本质
1-3An example of scientific inquiry :Darwin and Evolution 科学探究的一个例子：达尔文与进化论
1-4Unifying themes in biology 生物学统一主题
CHAPTER2 第二章
The Nature of Molecules and the Properties ofWater 分子的性质和水的性质
2-1The nature of atoms 原子的性质
Any substance in the universe that has mass and occupies space is defined as matter. All matter is composed of extremely small particles called atoms. Because of their size,atoms are difficult to study. Not utill early in the 20th century did scientists carry out the first experiments revealing the physical nature of atoms (figure2.1).
宇宙中任何有质量并占据空间的物质都被定义为物质。所有物质都是由称为原子的极小粒子组成的。由于原子的大小，很难研究。直到20世纪初，科学家们才进行第一次揭示原子物理性质的实验（图2.1）。
F2-1
Large-angle scattering of αparticles led Rutherford to the existence of the nucleus.
α粒子的大角度散射使卢瑟福得到了原子核的存在。
Atomic structure includes a centralnucleus and orbiting electrons
原子结构包括中心核和轨道电子
Objects as small as atoms can be seen only indirectly, by usingcomplex technology such as tunneling microscopy (figure 2.2).
像原子这样小的物体“只能通过使用隧道显微镜等复杂技术间接地观察到”（图2.2）。
We now know a great deal about the complexities of atomic structure, but the simple view put forth in 1913 by the Danish physicistNiels Bohr provides a good starting point for understanding atomictheory.
我们现在对原子结构的复杂性有了很多了解，但是丹麦物理学家尼尔斯·玻尔在1913年提出的简单观点为理解原子论提供了一个很好的起点。
Bohr proposed that every atom possesses an orbiting cloudof tiny subatomic particles called electrons whizzing around acore, like the planets of a miniature solar system.
玻尔提出，每个原子都有一个由微小的亚原子粒子组成的轨道云，这些粒子被称为电子，围绕着核心旋转，就像一个微型太阳系的行星。
At the center of each atom is a small, very dense nucleus formed of two other kindsof subatomic particles: protons and neutrons (figure 2.3).
在每个原子的中心都有一个小而致密的原子核，由另外两种亚原子粒子组成：质子和中子（图2.3）。
Atomic number
原子序数
Different atoms are defined by the number of protons, a quantitycalled the atomic number.
不同的原子是由质子的数量来定义的，质子的数量称为原子序数。
Atoms with the same atomic number(that is, the same number of protons) have the same chemical prop-erties and are said to belong to the same element.
原子序数相同的原子（即相同数量的质子）具有相同的化学性质，并被称为属于同一元素。
Formally speak-ing, an element is any substance that cannot be broken down to anyother substance by ordinary chemical means.
从形式上讲，元素是指任何不能用普通化学方法分解成其他物质的物质。
Within the nucleus, the cluster of protons and neutrons is held together by a force that works only over short, subatomic distances.
在原子核内，质子和中子团被一种只在短的亚原子距离内起作用的力聚集在一起。
Each proton carries a positive (+) charge, and each neu-tron has no charge. Each electron carries a negative (-) charge.
每个质子都带正（+）电荷，而每一个中子都没有电荷。每个电子都带负（-）电荷。
Typically, an atom has one electron for each proton and is thuselectrically neutral. The chemical behavior of an atom is due to the number and configuration of electrons, as we will see later inthis section.
一般来说，一个原子每一个质子有一个电子，因此是中性的。原子的化学行为是由电子的数量和结构决定的，我们将在后面的章节中看到。
Atomic mass
原子质量
The terms mass and weight are often used interchangeably, but theyhave slightly different meanings. Mass refers to the amount of asubstance, but weight refers to the force gravity exerts on a substance.
质量和重量这两个词经常互换使用，但它们的含义略有不同。质量是指物体的重量，而重量是指重力对物体施加的力。
An object has the same mass whether it is on the Earth orthe Moon, but its weight will be greater on the Earth because theEarths gravitational force is greater than the Moons.
一个物体无论在地球上还是在月球上都有相同的质量，但它在地球上的重量会更大，因为地球的引力大于月球的引力。
The atomic mass of an atom is equal to the sum of the masses of its protons and neutrons. Atoms that occur naturally on Earth contain from 1 to 92 protons and up to 146 neutrons.
原子的原子质量等于它的质子和中子的质量之和。地球上自然存在的原子含有1到92个质子和146个中子。
F2-2
Scanning-tunneling microscope image. Thescanning-tunneling microscope is a nonoptical way of imaging thatallows atoms to be visualized. This image shows a lattice of oxygenatoms(dark blue) on a rhodium crystal (light blue).
图2.2扫描隧道显微镜图像。扫描隧道显微镜是一种非光学成像方式，它可以使原子可视化。这张图片显示了铑晶体（浅蓝色）上氧合物的晶格（深蓝色）。
F2-3
Basic structure of atoms. All atoms have anucleus consisting of protons and neutrons, except hydrogen, the smallest atom, which usually has only one proton and no neutrons in itsnucleus. Oxygen typically has eight protons and eight neutrons in itsnucleus. In the simple Bohr model of atoms pictured here, electronsspin around the nucleus at a relatively far distance.
原子的基本结构。所有的原子都有由质子和中子组成的无环，除了最小的原子氢，它的原子核通常只有一个质子，没有中子。氧的原子核通常有八个质子和八个中子。在这张图中的“简单玻尔模型”中，电子绕着原子核旋转，距离相对较远。
a. Atoms are depicted as a nucleus with a cloud of electrons (not shown to scale).b. The electrons are shown in discrete energy levels. These are described in greater detail in the text.
a. 原子被描绘成一个带有电子云的原子核（未按比例显示）。b.电子以离散的能级显示。这些在正文中有更详细的描述。
The mass of atoms and subatomic particles is measured in units called daltons. To give you an idea of just how small theseunits are, note that it takes 602 million million billion(6.02 x 10²³)daltons to make 1 gram (g). A proton weighs approximately 1 dal-ton (actually 1.007 daltons), as does a neutron (1.009 daltons).
原子和亚原子粒子的质量是用道尔顿单位来测量的。为了让你知道这些单位有多小，请注意，1克（g）需要6.02亿道尔顿（6.02×10²³）道尔顿。一个质子重约1道尔顿（实际上是1.007道尔顿），一个中子（1.009道尔顿）也是如此。
In contrast, electrons weigh only 1/1840 of a dalton, so they con-tribute almost nothing to the overall mass of an atom.
相比之下，电子的重量只有道尔顿的1/1840，所以它们对原子的总质量几乎没有贡献。
Electrons
电子
The positive charges in the nucleus of an atom are neutralized, or counterbalanced, by negatively charged electrons, which are located in regions called orbitals that lie at varying distances around the nucleus. Atoms with the same number of protons and electrons are electrically neutral- -that is, they have no net charge,and are therefore called neutral atoms.
原子核中的正电荷被负电荷的电子中和，或被负电荷电子抵消，负电荷电子位于原子核周围不同距离的轨道上。具有相同数量质子和电子的原子是电中性的，也就是说，它们没有净电荷，因此被称为中性原子。
Electrons are maintained in their orbitals by their attractionto the positively charged nucleus. Sometimes other forces overcomethis attraction, and an atom loses one or more electrons. In other cases, atoms gain additional electrons. Atoms in which the numberof electrons does not equal the number of protons are known asions, and they are charged particles.
电子通过吸引带正电的原子核而保持在轨道上。有时其他的力超过了引力，原子就会失去一个或多个电子。在其他情况下，原子获得额外的电子。电子数不等于质子数的原子称为原子，它们是带电粒子。
An atom having more protonsthan electrons has a net positive charge and is called a cation. Forexample, an atom of sodium (Na) that has lost one electron becomes a sodium ion (Na+), with a charge of + 1. An atom having fewer protons than electrons carries a net negative charge and iscalled an anion. A chlorine atom (Cl) that has gained one electron becomes a chloride ion (Cl ), with a charge of-1.
有更多质子电子的原子有一个净正电荷，称为阳离子。例如，一个失去一个电子的钠原子变成一个带+1电荷的钠离子（Na+）。质子比电子少的原子带净负电荷，称为负离子。获得一个电子的氯原子（Cl）变成带-1电荷的氯离子（Cl）。
Isotopes
同位素
Although all atoms of an element have the same number of pro-tons, they may not all have the same number of neutrons. Atoms ofa single element that possess different numbers of neutrons are called isotopes of that element.
虽然一个元素的所有原子都有相同数量的质子，但它们未必都有相同数量的中子。具有不同数量中子的单个元素的原子称为该元素的同位素。
Most elements in nature exist as mixtures of different isotopes. Carbon (C), for example, has three isotopes, all containing six protons (figure 2.4). Over 99% of the carbon found in nature exists as an isotope that also contains six neutrons.
自然界中的大多数元素是以不同等质的混合物存在的。例如，碳（C）有三种同位素，都含有六个质子（图2.4）。自然界中超过99%的碳是以同位素的形式存在的，它也含有六个中子。
Because the total mass of this isotope is 12 daltons (6 from protons plus 6 from neutrons), it is referred to as carbon-12 and is symbolized ¹²C. Most of the rest of the naturally occurring carbon is carbon-13, anisotope with seven neutrons. The rarest carbon isotope is carbon-14,with eight neutrons.
因为这种同位素的总质量是12道尔顿（6道尔顿来自质子，6道尔顿来自中子），它被称为碳-12，并被符号化为¹²C。其余大部分自然产生的碳是碳-13，一种含有7个中子的异硫同位素。最稀有的碳同位素是碳-14，有8个中子。
Some radioactive isotopes are more unstable than others,and therefore they decay more readily. For any given isotope,however, the rate of decay is constant.
有些放射性同位素比其他同位素更不稳定，因此它们更容易衰变。然而，对于任何给定的同位素，衰变速率是恒定的。
F2-4
The three most abundant isotopes of carbon. Isotopes of aparticular element have different numbers of neutrons.
三种最丰富的碳同位素。一种特殊元素的同位素有不同数量的中子。
The decay time is usually expressed as the half-life, the time it takes for one-half of the atomsin a sample to decay. Carbon-14, for example, often used in thecarbon dating of fossils and other materials, has a half-life of 5730 years. A sample of carbon containing 1 g of carbon- 14 today would contain 0.5 g of carbon-14 after 5730 years, 0.25 g11,460 years from now, 0.125 g 17,190 years from now, and so on. By determining the ratios of the different isotopes of carbon and other elements in biological samples and in rocks, scientists are able to accurately determine when these materials formed.。
衰变时间通常表示为半衰期，即样品中一半的原子衰变所需的时间。例如，碳-14通常用于化石和其他材料的碳年代测定，其半衰期为5730年。今天一个含有1克碳-14的碳样品在5730年后0.25克，1460年后0.125克，17190年后将含有0.5克碳-14，以此类推。通过测定生物样品和岩石中碳和其他元素不同同位素的比值，科学家能够准确地确定这些物质形成的时间。
Radioactivity has many useful applications in modern biol-ogy. Radioactive isotopes are one way to label, or tag, a specific molecule and then follow its progress, either in a chemical reactionor in living cells and tissue.
放射性在现代生物学中有许多有用的应用。放射性同位素是一种标记或标记特定分子的方法，然后跟踪它的进展，无论是在化学反应中，还是在活细胞和组织中。
The downside, however, is that theen ergetic subatomic particles emitted by radioactive substances have the potential to severely damage living cells, producing genetic mutations and, at high doses, cell death.
然而，缺点是放射性物质释放出的低能能亚原子粒子有可能严重损害活细胞，产生基因突变，高剂量时会导致细胞死亡。
Consequently, exposure to radiation is carefully controlled and regulated. Scientists who work with radioactivity follow strict handling protocols and wear radiation-sensitive badges to monitor their exposure overtime to help ensure a safe level of exposure.
因此，辐射暴露受到严格控制和管制。从事放射性工作的科学家遵循严格的处理规程，佩戴辐射敏感徽章，以监测其超时暴露，以确保安全的辐射水平。
Electrons determine the chemicalbehavior of atoms
原子的化学行为决定了电子的行为
The key to the chemical behavior of an atom lies in the number and arrangement of its electrons in their orbitals. The Bohr model ofthe atom shows inp>
原子化学行为的关键在于它的电子在轨道上的数量和排列。原子的玻尔模型显示，单个电子围绕着一个中心原子核，呈现出不同的圆形位元。这个简单的图片的问题在于它不能反映现实。现代物理学表明，我们无法在任何给定的时间精确定位任何单个电子的位置。事实上，电子可以在任何地方，从靠近原子核到离原子核无穷远。
A particular electron, however, is more likely to be in some areas than in others. An orbital is defined as the area around a nucleus where an electron is most likely to be found. These orbitals represent probability distributions for electrons---that is, regions more likely to contain an electron. Some electron orbitals near the nucleus are spherical (s orbitals), where as others are dumbbellshaped (p orbitals) (figure 2.5). Still other orbitals, farther away from the nucleus, may have different shapes. Regardless of its shape, no orbital can contain more than two electrons.
然而，一个特定的电子在某些区域比在其他区域更可能存在。轨道被定义为原子核周围最有可能发现电子的区域。这些轨道代表了电子的概率分布，也就是说，更可能包含电子的区域。一些是球状轨道，有些是球形轨道（图2.5）。还有一些离原子核较远的轨道可能有不同的形状。不管它的形状如何，没有一个轨道能包含两个以上的电子。
Almost all of the volume of an atom is empty space. This is because the electrons are usually far away from the nucleus, rela-tive to its size. If the nucleus of an atom were the size of a golfball, the orbit of the nearest electron would be a mile away. Consequently, the nuclei of two atoms never come close enough innature to interact with each other. It is for this reason that an atoms electrons, not its protons or neutrons, determine its chemical behavior, and it also explains why the isotopes of an element, all of which have the same arrangement of electrons, behave the same way chemically.
一个原子几乎所有的体积都是空的。这是因为电子通常远离原子核，与原子核的大小有关。如果原子核的大小和高尔夫球一样大，那么最近的电子的轨道将在一英里之外。因此，两个原子的原子核在本质上从来没有接近到相互作用的程度。正是因为这个原因，一个原子的电子，而不是它的质子或中子，决定了它的化学行为，这也解释了为什么一个元素的同位素，所有这些元素都有相同的电子排列，其化学行为是一样的。
F2-5
Electron orbitals.
电子轨道。
a. The lowest energy level, orelectron shell--- the one nearest the nucleus---is level K. It is occupied by a single s orbital, referred to as 1s. b. The next highest energy level, L, isoccupied by four orbitals: one s orbital (referred to as the 2s orbital) and three p orbitals (each referred to as a 2p orbital). Each orbital holds two paired electrons with opposite spin. Thus, the K level is populated by two electrons, and the L level is populated by a total of eight electrons.c. The neon atom shown has the L and K energy levels completely filled with electrons and is thus unreactive.
a： 最低能级，电子壳层（离原子核最近的）是K级。它被一个s轨道占据，称为1s. b：下一个最高能级L由四个轨道构成：一个s轨道（称为2s轨道）和三个p轨道（每个轨道称为2p轨道）。每个轨道都有两个自旋相反的成对电子。因此，K能级由两个电子填充，而L能级由总共八个电子填充。
c：所示的氖原子的L和K能级完全充满了电子，因此是不活跃的。
Atoms contain discrete energy levels
原子包含离散的能级
Because electrons are attracted to the positively charged nucleus, it takes work to keep them in their orbitals, just as it takes work to hold a grapefruit in your hand against the pull of gravity. The for-mal definition of energy is the ability to do work.
因为电子被带正电荷的原子核所吸引，所以要使它们保持在轨道上是需要努力的，就像在你的手上拿一个葡萄柚来抵抗重力一样。能量的定义是做功的能力。
The grapefruit held above the ground is said to possess potential energy because of its position. If you release it, the grapefruit falls, and its potential energy is reduced. On the other hand,if you carried the grapefruit to the top of a building, you would increase its potential energy.
葡萄柚被放在地上，因为它的位置而具有势能。如果你释放它，葡萄柚就会掉下来，它的势能就会降低。另一方面，如果你把葡萄柚带到楼顶，你会增加它的势能。
Electrons also have a potential energy that is related to their position. To oppose the attraction of the nucleus and move the electron to a more distant orbital requires an input of energy, which results in an electron with greater potential energy. The chlorophyll that makes plants green captures energy from light during photosynthesis in this way.
电子也有与其位置有关的势能。为了对抗原子核的吸引力，并将电子移到更远的轨道上，需要输入能量，这会导致电子具有更大的势能。使植物变绿的叶绿素以这种方式在光合作用过程中从光中获取能量。
As youll see in chapter 8---light energy excites electrons in the chlorophyll molecule. Moving an electron closer to the nucleus has the opposite effect: Energy is released, usually as radiant energy(heat or light), and the electron ends up with less potential energy(figure 2.6).
正如你在第八章中看到的---光能激发叶绿素分子中的电子。把一个电子移到离原子核更近的地方会产生相反的效果：能量被释放，通常是辐射能（热或光），最后电子的势能就更少了（图2.6）。
One of the initially surprising aspects of atomic structure is that electrons within the atom have discrete energy levels. These discrete levels correspond to quanta (singular, quantum), which means specific amount of energy. To use the grapefruit analogy again, it is as though a grapefruit could only be raised to particular floors of a building. Every atom exhibits a ladder of potential energy values, a discrete set of orbitals at particular energetic “distances” from the nucleus.
原子结构最初令人惊讶的一个方面是原子内的电子具有离散的能级。这些离散的能级对应于量子（奇异的，量子），这意味着特定的能量量。再次使用葡萄柚的比喻，就好像葡萄柚只能被提升到建筑物的特定楼层。每一个原子都有一个势能值的阶梯，一组离原子核有特定能量“距离”的离散轨道。
Because the amount of energy an electron possesses is related to its distance from the nucleus, electrons that are the same distance from the nucleus have the same energy, even ifthey occupy different orbitals. Such electrons are said to occupy the same energy level. The energy levels are denoted with letters K, L, M, and so on (figure 2.6). Be careful not to confuse energy levels, which are drawn as rings to indicate an electrons energy, with orbitals, which have a variety of three-dimensional shapes and indicate an electrons most likely location.
因为一个电子所拥有的能量与它与原子核的距离有关，所以与原子核距离相同的电子即使占据不同的轨道，也具有相同的能量。这种电子被称为占据相同的能级。能级用字母K、L、M等表示（图2.6）。小心不要混淆能级，它们被画成环来表示电子的能量，与轨道相混淆，轨道有各种各样的三维形状，表明电子最可能的位置。
Electron orbitals are arranged so that as they are filled, this fills each energy level in successive order. This filling of orbitals and energy levels is what is responsible for the chemical reactivityof elements.
电子轨道的排列是这样的，当它们被填满时，它们会以连续的顺序填满每个能级。轨道和能级的填充是元素化学反应性的原因。
During some chemical reactions, electrons are transferred from one atom to another. In such reactions, the loss of an electronis called oxidation, and the gain of an electron is called reduction.
在某些化学反应中，电子从一个原子转移到另一个原子。在这种反应中，电子的损失称为氧化，而电子的增加称为还原。
Notice that when an electron is transferred in this way, it keeps its energy of position. In organisms, chemical energy isstored in high-energy electrons that are transferred from one atom to another in reactions involving oxidation and reduction (describedin chapter 7). When the processes of oxidation and reduction are coupled, which often happens, one atom or molecule is oxidized,while another is reduced in the same reaction. We call these combinations redox reactions.
注意，当一个电子以这种方式转移时，它保持着它的位置能量。在生物体中，化学能储存在高能电子中，这些电子在氧化和还原反应中从一个原子转移到另一个原子（见第7章）。当氧化和还原过程耦合时，通常会发生一个原子或分子被氧化，而另一个原子或分子在同一个反应中被还原。我们称之为氧化还原反应。
Learning Outcomes Review 2.1
学习成果回顾2.1
An atom consists of a nucleus of protons and neutrons surrounded by a cloud of electrons. For each atom, the number of protons is the atomic number; atoms with the same atomic number constitute an element, Atoms of a single element that
have different numbers of neutrons are called isotopes. Electrons,which determine the chemical behavior of an element, are
located about a nucleus in orbitals representing discrete energy levels. No orbital can contain more than two electrons, but each energy level consists of multiple orbitals, and thus contains many electrons with the same energy.
If the number of protons exceeds the number of neutrons, is the charge on the atom positive or negative?
If the number of protons exceeds electrons?
原子由质子和中子组成的原子核被电子云包围。对于每个原子，质子的数目就是原子序数；原子序数相同的原子构成一个元素，一个元素的原子有不同数量的中子被称为同位素。决定元素化学行为的电子是位于代表离散能级轨道上的原子核附近。没有一个轨道可以包含两个以上的电子，但是每个能级都由多个轨道组成，因此包含了许多具有相同能量的电子。
如果质子数超过中子数，原子上的电荷是正电荷还是负电荷？
如果质子的数量超过了电子呢？
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