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  • General

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  • 酸和碱基

    What you will learn
    ::你会学到什么

    • The properties of acids and bases
      ::酸和碱基的特性
    • How acids and bases are important in living organisms
      ::酸和碱对活生物体的重要性如何

    Two laboratory glassware pieces containing red and purple liquids, representing acids and bases.

    Acids and bases. Why are these important in biology?
    ::酸和碱,为什么这些在生物学中重要?

    It comes back to a number of biological processes. For example, work best at specific levels of acids or bases. Take your stomach , a very acidic environment. The enzymes that work in that environment could not work in your mouth. What would your food taste like if your mouth was also a very acidic environment?
    ::它可以追溯到一些生物过程。例如,在特定水平的酸或基底上工作最有效。你的胃,一个非常酸化的环境。在那个环境中工作的酶不能在你的嘴里工作。如果你的嘴也是非常酸化的环境,你的食物会是什么味道呢?

    Acids and Bases
    ::酸和碱基

    is the main ingredient of many solutions. A solution is a mixture of two or more substances that has the same composition throughout. Some solutions are acids and some are bases. To understand acids and bases, you need to know more about pure water. In pure water (such as distilled water), a tiny fraction of water molecules naturally breaks down to form ions . An ion is an electrically charged atom or molecule. The breakdown of water is represented by the chemical equation
    ::溶液是由两种或两种以上物质混合而成的,其成分在整体上相同。有些溶液是酸,有些是碱基。为了了解酸和碱,你需要了解更多关于纯水的知识。在纯水(如蒸馏水)中,水分子的一小部分自然分解成离子。离子是一种电荷原子或分子。水的分解由化学方程式代表。

    2 H 2 O → H 3 O + + OH -
    ::2 H2O H3O+ + OH-

    The products of this reaction are a hydronium ion (H 3 O + ) and a hydroxide ion (OH - ). The hydroxide ion, which has a negative charge, forms when a water molecule gives up a positively charged hydrogen ion (H + ). The hydronium ion, which has positive charge, forms when another water molecule accepts the hydrogen ion.
    ::这种反应的产物是氢离子(H3O+)和氢氧化离子(OH-),具有负电荷的氢氧化离子在水分子放弃正电氢离子(H+)时形成,具有正电荷的氢离子在水分子接受氢离子时形成。

    Acidity and pH
    ::酸性和pH值

    The concentration of hydronium ions in a solution is known as acidity . In pure water, the concentration of hydronium ions is very low; only about 1 in 10 million water molecules naturally breaks down to form a hydronium ion. As a result, pure water is essentially neutral. Acidity is measured on a scale called pH , as shown in Figure . Pure water has a pH of 7, so the point of neutrality on the pH scale is 7.
    ::溶液中氢离子的浓度被称为酸性。在纯水中,氢离子的浓度非常低;只有1 000万个水分子自然分解,形成氢离子。因此,纯水基本上是中性的。如图所示,酸性测量尺度称为pH。纯水的pH值为7,因此pH值的中性点为7。

    pH scale showing acidity and alkalinity levels of various substances from 0 to 14.
    Acidity and the pH scale: Water has a pH of 7, so this is the point of neutrality on the pH scale. Acids have a pH less than 7, and bases have a pH greater than 7. Approximate pH of examples are shown.

    Acids
    ::酸酸

    If a solution has a higher concentration of hydronium ions than pure water, it has a pH lower than 7. A solution with a pH lower than 7 is called an acid . As the hydronium ion concentration increases, the pH value decreases. Therefore, the more acidic a solution is, the lower its pH value is. Did you ever taste vinegar? Like other acids, it tastes sour. Stronger acids can be harmful to organisms. For example, stomach acid would eat through the stomach if it were not lined with a layer of mucus . Strong acids can also damage materials, even hard materials such as glass.
    ::如果溶液的氢离子浓度高于纯水,则其pH值低于7,则其pH值低于7。pH值低于7的溶液称为酸。当氢离子浓度增加时,pH值下降。因此,酸性越低,其pH值就越低。溶液酸度越低。你有没有尝过醋?与其他酸一样,它尝过酸味。强酸可能对生物有害。例如,如果胃酸不与一层粘结,则胃酸会通过胃部吞食。强酸也会损害材料,甚至玻璃等硬材料。

    Bases
    ::基底

    If a solution has a lower concentration of hydronium ions than pure water, it has a pH higher than 7. A solution with a pH higher than 7 is called a base . Bases, such as baking soda, have a bitter taste. Like strong acids, strong bases can harm organisms and damage materials. For example, lye can burn the skin, and bleach can remove the color from clothing.
    ::如果溶液的氢离子浓度低于纯水,则其pH值高于7.7, 其pH值高于7的溶液被称为基底。 碱基,如烘制苏打,具有苦味。 像强酸一样,强基会伤害生物和破坏物质。 比如,碱能烧伤皮肤,漂白能去除衣着的颜色。

    Check your understanding!
    ::检查你的理解!

     

     

    Acids and Bases in Organisms
    ::生物体中的酸和碱

    Acids and bases are important in living things because most enzymes can do their job only at a certain level of acidity. secrete acids and bases to maintain the proper pH for enzymes to work. For example, every time you digest food, acids and bases are at work in your . Consider the acidic environment of the stomach. The acidic environment helps with the digestion of food. The enzyme pepsin , which helps break down in the stomach can only function optimally in the low pH environment. The stomach secretes a strong acid that allows pepsin to work, and the stomach to do its job. However, when stomach contents enter the , the acid must be neutralized. This is because enzymes in the small intestine need a basic environment in order to work. An organ called the pancreas secretes a strong base into the small intestine, and this base neutralizes the acid.
    ::酸和碱在生物中很重要,因为大多数酶只能在一定的酸度上做它们的工作。 秘密酸和碱可以维持适当的pH值, 以保持酶正常工作。 例如, 每次你消化食物、 酸和碱值时, 都会工作。 想想胃酸环境。 酸环境有助于食物的消化。 有助于胃破裂的酶只能在低pH值环境中最优化地发挥作用。 胃部会分泌一种强酸, 允许pepsin工作, 腹部也能工作。 但是, 当胃内的东西进入工作时, 酸必须中和。 这是因为小肠中的酶需要一个基本的环境来工作。 一种叫做 Pancreas 的器官将坚固的基点植入小肠脏, 而这个基将酸中和。

     

     

     

    DID YOU KNOW?
    A bee sting is made up of various components that make the bee venom slightly acidic in nature with a pH between 5 to 5.5.
     

    Summary
    ::摘要

    • A solution is a mixture of two or more substances that has the same composition throughout. Some solutions are acids, some are bases.
      ::一种溶液是由两种或两种以上物质混合而成,其成分自始至终相同。有些溶液是酸,有些是碱。
    • Pure water has a pH of 7, so the point of neutrality on the pH scale is 7.
      ::纯净水的pH值为7,所以pH值的中点为7。
    • Acids have a higher concentration of hydronium ions than pure water, and a pH lower than 7.
      ::酸的氢离子浓缩度高于纯水,pH值低于7。
    • Bases have a lower concentration of hydronium ions than pure water, and a pH higher than 7.
      ::碱的氢离子浓缩度低于纯水,pH值高于7。
    • Acids and bases are important in living organisms because most enzymes function best at a specific pH.
      ::酸和碱在活生物体中很重要,因为大多数酶在特定pH值中功能最佳。

    Review
    ::回顾

    1. What is the pH of a neutral solution?
      ::中性解决办法的pH值是什么?
    2. Distinguish between an acid and a base.
      ::区分酸和碱。
    3. Describe an example of an acid or a base that is involved in human digestion.
      ::描述一个涉及人类消化的酸或碱的例子。
    4. Assume that you test an unknown solution and find that it has a pH of 7.2. What type of solution is it? How do you know?
      ::假设你测试了一个未知的解决方案 发现它pH值为7.2。这是哪种解决方案? 你怎么知道?
    5. Are the following acids or bases?
      1. milk
        ::牛奶牛奶
      2. coffee
        ::咖啡咖啡咖啡
      3. soap
        ::肥皂肥皂

      ::下列酸或碱?奶咖啡肥皂