Section outline

  • General

    Collapse all Expand all

  • 唇唇

    What you will learn
    ::你会学到什么

    • What are lipids
      ::何为脂质,何为脂质
    • Structure and function of saturated and unsaturated fatty acids
      ::饱和和和不饱和脂肪酸的结构和功能
    • Types of lipids
      ::脂脂类
    • Role of lipids in the
      ::B. 油脂和油脂在

    A glass filled with water has oil droplets floating on the surface, demonstrating oil's immiscibility.

    Oil. Does it mix with water? No. Biologically, why is this important?
    ::石油,它和水混合吗?

    Oil is a lipid. The property of chemically not being able to mix with gives lipids some very important biological functions. Lipids form the outer membrane of . Why?
    ::石油是一种脂质,化学上无法与脂质混合的特性使脂质具有一些重要的生物功能。脂质形成外膜。为什么?

    Lipids
    ::唇唇

    A lipid is an such as fat or oil. Organisms use lipids to store energy , but lipids have other important roles as well. Lipids consist of repeating units called fatty acids . Fatty acids are organic compounds that have the general formula CH 3 (CH 2 ) n COOH, where n usually ranges from 2 to 28 and is always an even number. There are two types of fatty acids: saturated fatty acids and unsaturated fatty acids.
    ::脂肪是一种脂质,如脂肪或油脂。生物体使用脂质储存能量,但脂质也有其他重要作用。脂质由称为脂肪酸的重复单位组成。脂肪酸是有机化合物,具有普通的 CH3(CH2)nCOOH, 通常在2至28之间, 并且始终是偶数。有两种脂肪酸:饱和脂肪酸和不饱和脂肪酸。

    DID YOU KNOW?
    Lipids are the highest long​-term energy storage molecules. One gram of lipids yields 9 kcal of energy.  
     

    Saturated Fatty Acids
    ::饱饱和脂肪酸

    In saturated fatty acids , carbon atoms are bonded to as many hydrogen atoms as possible. This causes the molecules to form straight chains, as shown in the Figure . The straight chains can be packed together very tightly, allowing them to store energy in a compact form. This explains why saturated fatty acids are solids at room temperature. use saturated fatty acids to store energy.
    ::在饱和脂肪酸中,碳原子与尽可能多的氢原子相连。这导致分子形成直链,如图所示。直链可以非常紧紧地包装在一起,允许它们以紧凑的形式储存能量。这解释了饱和脂肪酸为什么在室温下是固态的。使用饱和脂肪酸储存能量。

     
    • Structures of saturated, monounsaturated, and polyunsaturated fatty acids demonstrating molecular differences.
       
    • Examples of saturated and unsaturated fatty acids with molecular structures.
    Fatty Acids structures and their examples. Saturated fatty acids have straight chains. Unsaturated fatty acids have bent chains.  

    Unsaturated Fatty Acids
    ::不饱和脂肪酸

    In unsaturated fatty acids , some carbon atoms are not bonded to as many hydrogen atoms as possible. Instead, they are bonded to other groups of atoms. Wherever carbon binds with these other groups of atoms, it causes chains to bend (see the Figure ). The bent chains cannot be packed together very tightly, so unsaturated fatty acids are liquids at room temperature. Plants use unsaturated fatty acids to store energy. Some examples are shown in the Figure .
    ::在不饱和脂肪酸中,一些碳原子没有与尽可能多的氢原子连接起来。相反,它们与其他原子组捆绑在一起。如果碳与其他原子组捆绑在一起,就会导致链条弯曲(见图 )。弯曲的链条不能非常紧凑地包装在一起,所以不饱和脂肪酸是室内温度下的液体。植物使用不饱和脂肪酸储存能量。一些例子见图 。

     
    • Various oils in small bottles, sunflower seeds, and a sunflower bloom.
    • A mix of nuts and dried fruits, highlighting sources of unsaturated fatty acids.
    • Bottles of olive oil surrounded by fresh green olives, illustrating unsaturated fatty acids.
    These plant products all contain unsaturated fatty acids.

    Types of Lipids
    ::利皮类型

    Lipids may consist of fatty acids alone, or they may contain other molecules as well. For example, some lipids contain alcohol or phosphate groups. They include
    ::脂液可能单由脂肪酸组成,也可能含有其他分子,例如,一些脂质含有酒精或磷酸盐类。

    1. Triglycerides : the main form of stored energy in animals.
      ::三甘酸酯:动物体内储存能量的主要形式。
    2. Phospholipids : the major components of .
      ::磷脂:
    3. Steroids : serve as chemical messengers and have other roles.
      ::类固醇:充当化学送信员,并发挥其他作用。
    A triglyceride molecule showing glycerol and three fatty acid chains.
    Triglyceride Molecule. The left part of this triglyceride molecule represents glycerol. Each of the three long chains on the right represents a different fatty acid.

    Lipids and Diet
    ::嘴唇和饮食

    Humans need lipids for many vital functions, such as storing energy and forming cell membranes. Lipids can also supply cells with energy. In fact, a gram of lipids supplies more than twice as much energy as a gram of or . Lipids are necessary in the diet for most of these functions. Although the human body can manufacture most of the lipids it needs, there are others, called essential fatty acids , that must be consumed in food . Essential fatty acids include omega-3 and omega-6 fatty acids. Both of these fatty acids are needed for important biological processes, not just for energy.
    ::人类需要脂质,例如储存能量和形成细胞膜等许多关键功能。利皮也可以为细胞提供能量。事实上,一克脂质的能量比一克或一克多一倍以上。在大部分这些功能的饮食中,脂质是必要的。虽然人体可以制造它所需要的大部分脂质,但还有一些叫做基本脂肪酸的脂肪酸必须用在食物中。基本脂肪酸包括 omega-3 和 omega-6 脂肪酸。这两种脂肪酸都是重要的生物过程所需要的,而不仅仅是能量。

    DID YOU KNOW?
    The acidic environment of the stomach helps digest lipids by activating the lipase. Lipase breaks down lipids into glycerol and fatty acids.  
     

    Although some lipids in the diet are essential, excess dietary lipids can be harmful. Because lipids are very high in energy, eating too many may lead to unhealthy weight gain. A high-fat diet may also increase lipid levels in the . This, in turn, can increase the risk for health problems such as . The dietary lipids of most concern are saturated fatty acids, trans fats, and cholesterol. For example, cholesterol is the lipid mainly responsible for narrowing arteries and causing the disease atherosclerosis .
    ::尽管饮食中的某些脂质是必需的,但过多的饮食脂质可能是有害的,因为脂质在能量中非常高,吃太多就会导致不健康的体重增加。高脂肪饮食也会增加脂肪含量。这反过来会增加健康问题的风险,例如:最受关注的饮食脂质是饱和脂肪酸、跨脂肪和胆固醇。例如,胆固醇是导致动脉缩小和导致疾病塞罗斯硬化的主要脂肪。

     

     

     

    Summary
    ::摘要

    • Organisms use lipids to store energy. There are two types of fatty acids: saturated fatty acids and unsaturated fatty acids.
      ::生物利用脂肪储存能量,有两种脂肪酸:饱和脂肪酸和不饱和脂肪酸。
    • Animals use saturated fatty acids to store energy. Plants use unsaturated fatty acids to store energy.
      ::动物用饱和脂肪酸储存能量,植物用不饱和脂肪酸储存能量。
    • Phospholipids are the major components of cell membranes.
      ::磷脂是细胞膜的主要成分。
    • Excess dietary lipids can be harmful.
      ::过量的饮食脂质可能有害。

    Review
    ::回顾

    1. What is a lipid? Give three examples.
      ::什么是脂质?举三个例子。
    2. Butter is a fat that is a solid at room temperature. What type of fatty acid does butter contain? How do you know?
      ::黄油是一种在室温下是固体的脂肪。黄油含有何种脂肪酸? 你怎么知道?
    3. Explain why molecules of saturated and unsaturated fatty acids have different shapes.
      ::解释为什么饱和和和不饱和脂肪酸的分子有不同的形状。
    4. Which lipid is the main component of cell membranes?
      ::哪个脂质是细胞膜的主要成分?