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  • 利皮

    Nutrition facts label displaying fat content and other nutrients in a food product.

    You’ve probably seen dozens of nutrition facts labels like the one in the opening image. The labels show the nutrients that foods contain. Many people read nutrition facts labels to see how much fat there is in particular foods. That’s because eating too much fat, especially saturated fat, can be unhealthy and contribute to gain. Fats are a type of called lipids.
    ::你可能已经看到过几十个营养事实标签,比如开张图像中的标签。 标签显示了食物所含有的营养成分。 许多人阅读营养事实标签,以了解食物中究竟有多少脂肪。 这是因为吃太多脂肪,特别是饱和脂肪,可能不健康,而且有助于增益。 脂肪是一种所谓的脂质。

    What Are Lipids?
    ::什么是利皮人?

    Lipids are one of four classes of biochemical compounds, which are compounds that make up living things and carry out life processes. (The other three classes of biochemical compounds are , , and .) Living things use lipids to store . Lipids are also the major components of cell membranes in living things. Types of lipids include fats and oils.
    ::利皮是生物化学化合物的四个类别之一,它们是构成活物和进行生命过程的化合物。 (其他三种生物化学化合物是,和......)活物使用脂质储存。利皮也是细胞膜中活物的主要成分。 脂肪的类型包括脂肪和油。

    • Fats are lipids that animals use to store energy.
      ::脂肪是动物用来储存能量的脂肪。
    • Oils are lipids that plants use to store energy.
      ::油是植物用来储存能源的脂肪

    Q: Can you name some lipids that are fats? What are some lipids that are oils?
    ::问:你能说出一些脂肪的脂质吗?什么是油质的脂质?

    A: Lipids that are fats include butter and the fats in meats. Lipids that are oils include olive oil and vegetable oil. Examples of both types of lipids are pictured in the Figure .
    ::甲:脂肪的脂脂包括黄油和肉类中的脂肪;油的脂脂包括橄榄油和植物油;图中列出了这两种脂类的例子。

    Grilled lamb chops showing fat; a bottle of olive oil on a countertop.

    (A) The white bands on these lamb chops are fat. (B) The yellow liquid in this bottle is olive oil.
    :伤心A) 这些羊排上的白带是脂肪。 (B) 这个瓶子里的黄色液体是橄榄油。

    Fatty Acids
    ::脂肪酸

    Lipids consist only or mainly of carbon, hydrogen, and oxygen. Both fats and oils are made up of long chains of carbon atoms that are bonded together. These chains are called fatty acids. Fatty acids may be saturated or unsaturated. In the Figure you can see structural formulas for two small fatty acids, one saturated and one unsaturated.
    ::利皮只由碳、氢和氧组成,脂肪和油都是由长链的碳原子组成,这些碳原子结合在一起。这些链条被称为脂肪酸。脂肪酸可以是饱和的,也可以是不饱和的。在图中,你可以看到两种小脂肪酸的结构公式,一种是饱和的,一种是不饱和的。

    • Saturated fatty acids have only single bonds between carbon atoms. As a result, the carbon atoms are bonded to as many hydrogen atoms as possible. In other words, the carbon atoms are saturated with hydrogens. Saturated fatty acids are found in fats.
      ::饱和脂肪酸在碳原子之间只有单一联系。 因此,碳原子与尽可能多的氢原子相连。 换句话说,碳原子与氢饱和。 饱和脂肪酸存在于脂肪中。
    • Unsaturated fatty acids have at least one double bond between carbon atoms. As a result, some carbon atoms are not bonded to as many hydrogen atoms as possible. They are unsaturated with hydrogens. Unsaturated fatty acids are found in oils.
      ::不饱和脂肪酸在碳原子之间至少有一个双倍联系。 因此,有些碳原子没有与尽可能多的氢原子连接起来。 它们与氢不饱和。 在油类中发现了不饱和脂肪酸。

    Structural formulas for saturated and unsaturated fatty acids, highlighting their carbon and hydrogen bonds.

    Q: Both of these fatty molecules have six carbon atoms and two oxygen atoms. How many hydrogen atoms does each fatty acid molecule contain? What else is different about the two molecules?
    ::问题:这两个脂肪分子都有六个碳原子和两个氧原子。每个脂肪酸分子含有多少氢原子?这两个分子还有什么不同?

    A: The saturated fatty acid molecule has 12 hydrogen atoms. This is as many hydrogen atoms as can possibly be bonded to carbon atoms in this molecule. The unsaturated fatty acid molecule has 10 hydrogen atoms, or two less than the maximum possible number. The saturated fatty acid has only single bonds between its carbon atoms. The unsaturated fatty acid has a double bond between two of its carbon atoms.
    ::A:饱和脂肪酸分子有12个氢原子。这是尽可能多的氢原子可能与该分子中的碳原子相连接。不饱和脂肪酸分子有10个氢原子,或比可能的最大数量少两个。饱和脂肪酸在其碳原子之间只有单一的联结。不饱和脂肪酸在其两个碳原子之间有双重联结。

    Phospholipids
    ::磷脂

    Some lipids contain the phosphorus as well as carbon, hydrogen, and oxygen. These lipids are called . Two layers of phospholipid molecules make up the cell membranes of living things. In the Figure , you can see how phospholipid molecules are arranged in a cell membrane.
    ::有些脂质既含有磷,也含有碳、氢和氧。这些脂质被称为 。两层磷素分子构成活物的细胞膜。在图中,你可以看到磷素分子是如何在细胞膜中排列的。

    • One end of each phospholipid molecule is polar , so it has a partial electric charge . Water is also polar and has electrically charged ends, so it is attracted to the oppositely charged end of a phospholipid molecule. This end of the phospholipid molecule is described as hydrophilic, which means “water loving.”
      ::每个磷素分子的一端是极性的,因此它有部分电荷。水也是极性的,有电荷端,因此它被磷素分子的反向电荷端吸引。磷素分子的这一端被描述为水利,这意味着“爱水 ” 。
    • The other end of each phospholipid molecule is nonpolar and has no electric charge. This end of the phospholipid molecule repels polar water and is described as hydrophobic, or “water hating.”
      ::每种磷素分子的另一端是非极化的,没有电荷。 磷素分子的这一端是极地水,被称为疏水或“防水 ” 。

    Arrangement of phospholipid molecules in a cell membrane, illustrating hydrophilic and hydrophobic ends.

    In the Figure , the hydrophilic ends of the phospholipid molecules are on the outsides of the cell membrane, and the hydrophobic ends are on the inside of the cell membrane. This arrangement of phospholipids allows some substances to pass through the cell membrane while keeping other substances out. 
    ::在图中,磷素分子的流利端位于细胞膜外部,疏水端位于细胞膜内,磷素的这种安排允许某些物质通过细胞膜,同时将其他物质挡在外面。

    Summary
    ::摘要

    • Lipids are a class of biochemical compounds that living things use to store energy. Types of lipids include fats and oils.
      ::利皮是生物物质用来储存能源的一类生化化合物,脂类包括脂肪和油类。
    • Both fats and oils consist of long chains called fatty acids, which may be saturated or unsaturated.
      ::脂肪和油都由长链组成,称为脂肪酸,可以饱和或不饱和。
    • Some lipids, called phospholipids, contain phosphorus as well as carbon, hydrogen, and oxygen. Two layers of phospholipid molecules make up the cell membranes of living things.
      ::一些脂质,叫做磷素,含有磷以及碳、氢和氧,两层磷素分子构成活物的细胞膜。

    Review
    ::回顾

    1. What are lipids?
      ::什么是脂质?
    2. Name two types of lipids.
      ::列出两种脂质。
    3. Describe fatty acids.
      ::描述脂肪酸。
    4. Relate the structure of phospholipids to their function in cell membranes.
      ::将磷素的结构与其在细胞膜中的功能联系起来。

    Explore More
    ::探索更多

    W atch the animation about lipid structure and function. Then answer the questions below. 
    ::观看关于脂质结构和功能的动画。 然后回答下面的问题。

    1. Give an example of a saturated fatty acid and an example of an unsaturated fatty acid.
      ::举一个饱和脂肪酸的例子和一个不饱和脂肪酸的例子。
    2. Contrast the shapes of saturated and unsaturated fatty acid molecules.
      ::对比饱和和和不饱和脂肪酸分子的形状。
    3. Relate the shape of saturated and unsaturated fatty acid molecules to their melting point and state at room temperature.
      ::将饱和和不饱和脂肪酸分子的形状与其熔点和室温状态相对应。