Section outline

  • General

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  • 碳的重要性

    What you will learn
    ::你会学到什么

    • The importance of carbon for life on Earth
      ::碳对地球上生命的重要性
    • The basic structure and function of the four major types of
      ::这四大类核武器的基本结构和功能的基本结构和功能

    Various representations of carbon's role in nature, including trees, animals, and pollution.

    Carbon. Element number six. Right in the middle of the first row of the Periodic Table. So what?
    ::碳元素六,在周期表第一排中间,那又怎样?

    Carbon is the most important element to life. Without this element, life as we know it would not exist. As you will see, carbon is the central element in compounds necessary for life.
    ::碳是生命中最重要的元素。没有这个元素,我们知道生命是不存在的。正如你们将看到的那样,碳是生命所需的化合物中的核心元素。

    The Significance of Carbon
    ::碳的重要性

    A compound found mainly in living things is known as an organic compound . Organic compounds make up the and other structures of organisms and carry out life processes. Carbon is the main element in organic compounds, so carbon is essential to life on Earth. Without carbon, life as we know it could not exist.
    ::一种主要存在于生物中的化合物被称为有机化合物,有机化合物构成有机体的结构和其他结构,并进行生命过程。碳是有机化合物中的主要元素,因此碳是地球上生命必不可少的。没有碳,我们知道生命不可能存在。

    DID YOU KNOW?
    was one of the first organic molecules that formed about 4 billion years ago. It may have formed the basis of early life. 
     

    Compounds
    ::化合物

    A compound is a substance that consists of two or more elements. A compound has a unique composition that is always the same. The smallest particle of a compound is called a molecule. Consider as an example. A molecule of water always contains one atom of oxygen and two atoms of hydrogen. The composition of water is expressed by the chemical formula H 2 O. A model of a water molecule is shown in the Figure  . Water is not an organic compound.
    ::一种化合物是由两个或两个以上元素组成的物质。一种化合物的独特成分始终相同。一种化合物的最小粒子称为分子。举例来说,一个水分子总是含有一个氧原子和两个氢原子。水的成分用化学公式H2O表示。一个水分子的模型在图中显示。水不是有机化合物。

    Model of a water molecule showing one red oxygen atom and two white hydrogen atoms.
    A water molecule always has this composition, one atom of oxygen and two atoms of hydrogen.

    What causes the atoms of a water molecule to “stick” together? The answer is chemical bonds . A chemical bond is a force that holds molecules together. Chemical bonds form when substances react with one another. A chemical reaction is a process that changes some chemical substances into others. A chemical reaction is needed to form a compound. Another chemical reaction is needed to separate the substances in a compound.
    ::导致水分子原子“粘合”的原因何在?答案是化学联系。化学联系是把分子放在一起的力量。当物质相互反应时,化学联系形成化学联系。化学反应是一种将某些化学物质改变为其他化学物质的过程。需要化学反应来形成化合物。需要另一种化学反应来将化合物中的物质分离出来。

    Carbon
    ::碳碳碳碳

    Why is carbon so basic to life? The reason is carbon’s ability to form stable bonds with many elements, including itself. This property allows carbon to form a huge variety of very large and complex molecules. In fact, there are nearly 10 million carbon-based compounds in living things! However, the millions of organic compounds can be grouped into just four major types: , , , and . You can compare the four types in the Table  . Common structural examples of the four major types of organic compounds are included in the table. Notice the diversity of structures among the organic compounds listed.  
    ::为什么碳是生命的基础? 原因是碳能与包括自身在内的许多元素形成稳定的联系。 碳能让碳形成各种非常大和复杂的分子。 事实上,生物物质中有近1 000万种碳化合物。 然而,数百万有机化合物可以仅仅分为四种主要类型: 、 、 、 和 。 您可以比较表中的四种类型。 表格中包含了四种主要有机化合物的常见结构例子。 注意所列有机化合物的结构多样性。

    Type of Compound Examples Structure Elements Functions Monomer
    Carbohydrates sugars, starches
    Chemical structure of a monosaccharide, illustrating its carbon, hydrogen, and oxygen composition.
    		carbon, hydrogen, oxygen provides energy to cells, stores energy, forms body structures monosaccharide
    Lipids fats, oils, phospholipids
    Molecular structures of lipids illustrating fatty acids and phospholipids related to membranes.
    		carbon, hydrogen, oxygen, phosphorous stores energy, forms , carries messages fatty acids
    Proteins , antibodies
    Representation of protein structure illustrating the significance of carbon in biological processes.
    		carbon, hydrogen, oxygen, nitrogen, sulfur helps cells keep their shape, makes up , speeds up chemical reactions, carries messages and materials amino acid
    Nucleic Acids , RNA
    A DNA double helix with colored strands representing nucleotides.
    		carbon, hydrogen, oxygen, nitrogen, phosphorus contains instructions for proteins, passes instructions from parents to offspring, helps make proteins nucleotide

    Carbohydrates, proteins, and nucleic acids are large molecules known as polymers (also referred to as macromolecules) built from smaller molecules ( monomers ) through dehydration reactions . In a dehydration reaction, water is removed as two monomers are joined together. Hydrolysis is a reaction where polymers are broken down; a water molecule is split, separating a monomer away from the polymer chain .
    ::碳水化合物、蛋白质和核酸是大型分子,称为聚合物(也称为大型分子),通过脱水反应从较小的分子(分子)中制造。在脱水反应中,脱水反应中,将水分除为两个单体结合。水解是聚合物分解的一种反应;水分子分裂,将单体从聚合物链分离出来。

    CAN YOU MATCH?
    Try to match these organic compounds with their major functions.  
     

     

    Summary
    ::摘要

    • Carbon is the main element in organic compounds. Carbon can form stable bonds with many elements, including itself.
      ::碳是有机化合物中的主要元素,碳可以形成稳定的联系,包括多种元素,包括碳本身。
    • There are four major types of organic compounds: carbohydrates, lipids, proteins, and nucleic acids.
      ::有机化合物有四种主要类型:碳水化合物、脂类、蛋白质和核酸。
    • In a dehydration reaction, two monomers are joined together while in hydrolysis polymers are broken down, separating a monomer away from the polymer chain.
      ::在脱水反应中,将两个单体结合在一起,而在水解聚合物中,将一个单体从聚合物链中分离出来。

    Review
    ::回顾

    1. What is a compound?
      ::什么是复合物?
    2. Explain why carbon is essential to all known life on Earth.
      ::解释为什么碳是地球上所有已知生命的关键。
    3. What are the four main types of organic compounds?
      ::有机化合物的四种主要类型是什么?
    4. Which type(s) of organic compounds provide energy?
      ::哪种类型的有机化合物能提供能源?
    5. Which organic compound stores genetic information?
      ::哪些有机化合物储存遗传信息?
    6. Examples of proteins include ____________.
      ::蛋白质的例子包括______________________________。