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    Protein Shake
    ::蛋白奶昔

    Drinks like this shake contain a lot of protein. Muscle tissue consists mainly of protein, so such drinks are popular with people who want to build muscle. Making up is just one of a plethora of functions of this amazingly diverse class of biochemicals.
    ::像这样的饮料含有大量的蛋白质。肌肉组织主要由蛋白质组成,因此这些饮料很受想要建立肌肉的人欢迎。组成这些饮料只是这一系列令人惊异的生化化学的众多功能之一。

    What Are Proteins?
    ::什么是蛋白质?

    Proteins  are a major class of biochemical compounds made up of small monomer molecules called amino acids .  More than  20 different amino acids are typically  found in the proteins of living things. Small proteins may contain just a few hundred amino acids, while  large proteins may contain thousands.
    ::蛋白质是一种主要的生化化合物,由叫做氨基酸的小型单体分子组成。 20多种不同的氨基酸通常存在于活物的蛋白质中。 小型蛋白质可能只含有几百种氨基酸,而大型蛋白质可能含有数千种。

    Protein Structure
    ::蛋白结构

    When amino acids bind together, they may form short chains of two or just a few amino acids. These short chains are called peptides . When amino acids form long chains, the chains are called polypeptides . A protein consists of one or more polypeptides.
    ::当氨基酸结合在一起时,它们可能形成两个或几个氨基酸的短链。这些短链被称为peptides。当氨基酸形成长链时,链被称为聚苯醚。蛋白质由一种或多种聚苯醚组成。

    Proteins may have up to four levels of structure, from primary to quaternary, as described and shown in the diagram . As a result, they can have  tremendous diversity. Here are some additional details about the levels of protein structure: 
    ::蛋白质的结构可能多达四个层次,从初至四,如图中所述和所示。因此,蛋白质可以具有巨大的多样性。关于蛋白质结构的更多细节如下:

    • A protein’s primary structure is the sequence of amino acids in its polypeptide chain(s). This sequence of amino acids determines the higher levels of protein structure, and it's encoded in genes .
      ::蛋白质的主要结构是其聚苯醚链中氨基酸的序列。 氨基酸的序列决定了更高层次的蛋白质结构,并编码在基因中。
    • A protein's secondary structure consists of r egularly repeating local structures, which are stabilized by chemical bonds . The most common secondary structures are  the alpha helix and beta sheet. Because secondary structures are local, many regions of different secondary structure can be present in the same protein molecule.
      ::蛋白质的二次结构包括经常重复的局部结构,这些结构由化学键稳定下来。 最常见的二次结构是阿尔法螺旋和贝塔薄片。 由于二级结构是局部的,许多不同的二级结构区域可能存在于相同的蛋白分子中。
    • A protein's tertiary structure  refers to the overall three-dimensional shape of a single protein molecule. It is determined by the spatial relationship between secondary structures. The tertiary structure is what controls the basic function of the protein.
      ::蛋白质的三级结构是指单一蛋白分子的三维整体形状,由二级结构之间的空间关系决定,三级结构控制蛋白质的基本功能。
    • Not all proteins have a final, quaternary structure. This is a  structure formed by several protein molecules that function together as a single protein complex.
      ::并非所有蛋白质都有一个最终的、四面形结构。这是一个由几个蛋白分子组成的结构,它们作为一个单一蛋白综合体一起运行。

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    This diagram shows the levels of structure of the protein hemoglobin.
    ::本图显示蛋白质血红蛋白的结构水平。

    Functions of Proteins
    ::蛋白质函数

    The diversity of protein structures explains why  this class of biochemical compounds can play so many important roles in living things. What are the roles of proteins?
    ::蛋白质结构的多样性解释了为什么这一类生化化合物可以在生物中扮演如此重要的角色。 蛋白质的作用是什么?

    • Some proteins have structural functions. They may help keep their shape or make up muscle tissues.
      ::有些蛋白质具有结构功能,可以帮助保持形状或形成肌肉组织。
    • Many proteins are that speed up chemical reactions in cells.  Enzymes are usually highly specific and accelerate only one or a few chemical reactions. Thousands of different are known to be catalyzed by enzymes, including most of the reactions involved in metabolism . A reaction without an enzyme might take millions of years to complete, whereas with the proper enzyme, it may take just a few milliseconds!
      ::许多蛋白质就是加速细胞中的化学反应。 酶通常非常具体,只加速一种或几种化学反应。 数千种不同的蛋白质已知被酶催化,包括大部分新陈代谢反应。 没有酶的反应可能需要数百万年时间才能完成,而适当的酶则只需要几毫秒!
    • Other proteins are antibodies , which bind to specific foreign substances, like  proteins on the surface of bacterial cells. This process targets the cells for destruction.
      ::其他蛋白质是抗体,与特定的外国物质结合,如细菌细胞表面的蛋白质,该过程针对细胞进行破坏。
    • Still other proteins carry messages or materials. Myoglobin, for example, is an oxygen-binding protein found in the muscle tissues of most mammals (including humans). You can see a model of the tertiary structure of myoglobin in the figure .
      ::还有一些蛋白质含有信息或材料。例如,Myoglobin是一种在大多数哺乳动物(包括人类)的肌肉组织中发现的含氧蛋白。您可以看到图中第三级血红蛋白结构的模型。

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    Myoglobin is a protein found in the muscle tissues of most mammals. It binds with oxygen, and in doing so, supplies the cells with oxygen.
    ::血红蛋白是大多数哺乳动物肌肉组织中发现的蛋白质,它与氧气结合,从而为细胞提供氧气。

    The chief characteristic of proteins that allows their diverse set of functions is their ability to bind to other molecules so specifically and tightly. Myoglobin can bind specifically and tightly with oxygen. The region of a protein responsible for binding with another molecule is known as the binding site. This site is often a depression on the molecular surface, determined largely by the tertiary structure of the protein.
    ::蛋白质允许其多种功能的主要特征是能够如此具体和紧密地与其他分子捆绑在一起。 Myoglobin可以具体和紧紧地与氧气绑在一起。 与另一个分子绑在一起的蛋白质区域被称为绑定地点。 这个地点往往是分子表面的抑郁症,主要由蛋白质的三级结构决定。

    Protein Consumption, Digestion, and Synthesis
    ::蛋白质消费、消化和合成

    Proteins are necessary in the diets of humans and other . We cannot make all the different amino acids we need, so we must obtain some of them from the foods we consume. In  the process of digestion , we break down the proteins in food into free amino acids that can then be used to synthesize our own proteins. from amino acid monomers takes place in all cells and is controlled by genes. Once new proteins are synthesized, they generally do not last very long before they are degraded and their amino acids are recycled. A protein's lifespan in mammalian cells is generally just a day or two.
    ::蛋白质在人类和其他人的饮食中是必需的。 我们无法制造我们所需要的所有不同的氨基酸, 因此我们必须从我们消费的食物中获取其中一些。 在消化过程中, 我们把食物中的蛋白质分解为免费的氨基酸, 然后可以用来合成我们自己的蛋白质。 从氨基酸单体到所有细胞中都出现, 并受基因控制。 一旦新蛋白质被合成, 它们一般不会在退化和回收其氨基酸之前很久就存在。 哺乳动物细胞中的蛋白质寿命一般只有一天或两天。

    Summary
    ::摘要

    • Proteins are a major class of biochemical compounds. They're made up of small monomer molecules called amino acids. More than 20 amino acids are commonly found in the proteins of living things. Proteins have tremendous diversity in terms of both structure and function.
      ::蛋白质是一种主要的生化化合物。 它们由小型单体分子组成, 叫做氨基酸。 20多种氨基酸通常存在于生物的蛋白质中。 蛋白质在结构和功能上都具有巨大的多样性。
    • Long chains of amino acids form polypeptides. The sequence of amino acids in polypeptides makes up the primary structure of proteins. Proteins also have higher levels of structure. Secondary structure refers to configurations — such as helices and sheets — within polypeptide chains. Tertiary structure is a protein's overall three-dimensional shape, which controls the molecule's basic function. A quaternary structure forms if multiple protein molecules join together and function as a complex.
      ::氨基酸的长链构成聚苯醚。聚苯胺中的氨基酸序列构成蛋白质的主要结构。蛋白质结构也较高。二次结构是指聚苯酯链内的配置——例如象虱子和床单。三级结构是蛋白质的三维整体形状,它控制分子的基本功能。如果多种蛋白分子结合在一起,并作为一个复杂体发挥作用,则四面结构形式。
    • Proteins  help cells keep their shape, make up muscle tissues, act as enzymes or antibodies, and carry messages or materials. The chief characteristic that allows proteins' diverse functions is their ability to bind specifically and tightly with other molecules.
      ::蛋白质帮助细胞保持其形状,组成肌肉组织,充当酶或抗体,并携带信息或材料。 蛋白质能发挥不同功能的主要特征是能够与其他分子具体和紧密地结合。
    • We cannot make all the amino acids we need to synthesize our own proteins, so we must obtain some of them from proteins in the foods we consume.
      ::我们不能用氨基酸来合成自己的蛋白质, 所以我们必须从我们消费的食物中的蛋白质中获取一些蛋白质。

    Review
    ::回顾

    1. What are proteins?
    ::1. 什么是蛋白质?

    2. Outline the four levels of protein structure.
    ::2. 概述蛋白质结构的四个层次。

    3. Identify four functions of proteins.
    ::3. 确定蛋白质的四个功能。

    4. Explain why proteins can take on so many different functions in living things.
    ::4. 解释为什么蛋白质可以在生物中承担如此多的不同功能。

    5. What is the role of proteins in the human diet?
    ::5. 蛋白质在人类饮食中的作用是什么?

    6. Can you have a protein with both an alpha helix and a beta sheet? Why or why not?
    ::6. 你能否同时拥有甲型螺旋和贝塔薄片的蛋白质?

    7. If there is a mutation in a gene that causes a different amino acid to be encoded than the one usually encoded in that position within the protein, would that affect:
    ::7. 如果基因发生突变,导致一种不同的氨基酸编码不同于通常在蛋白质内以该状态编码的酸编码,则会影响:

    a. The primary structure of the protein? Explain your answer.
    ::a. 蛋白质的主要结构?

    b. The higher structures (secondary, tertiary, quaternary) of the protein? Explain your answer.
    ::b. 蛋白质的较高结构(中等、高等、四甲状腺)?解释你的答复。

    c. The function of the protein? Explain your answer.
    ::c. 蛋白质的功能?

     

    8. What is the region of a protein responsible for binding to another molecule? Which level or levels of protein structure creates this region?
    ::8. 蛋白质对另一个分子的结合负责的区域是什么?蛋白质结构的哪一级或哪一级形成这个区域?

     

    9. Arrange the following in order from the smallest to the largest level of organization:
    ::9. 按组织级别从最小组织到最大组织级别排列如下:

    peptide; protein; amino acid; polypeptide
    ::Peptide;蛋白质;氨基酸;聚苯二酸

     

    10. True or False:  You can tell the function of all proteins based on  their quaternary structure.
    ::10. 真实或假:根据蛋白质的四面体结构,可以辨别所有蛋白质的功能。

     

    11. Explain what the reading means when it says that amino acids are “recycled.”
    ::11. 解释读数表示氨基酸 " 循环利用 " 意味着什么。

    Explore More
    ::探索更多

    Watch the video below to learn  about how proteomics (the study of proteins) can be used in  cancer research.  
    ::了解如何将蛋白质组学(蛋白质研究)用于癌症研究。

     

     Learn about muscle protein synthesis and breakdown in the video below. 
    ::了解肌肉蛋白质合成和以下视频中的分解。

     

     The video below discusses the different  levels of protein structure.
    ::以下视频讨论不同层次的蛋白质结构。