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  • 光相合成反应 - 高级

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    What is the most common biochemical reaction ever?
    ::最常见的生化反应是什么?

    Well, it may or may not be this one. Every split second that sunlight strikes a plant's leaf, the process of photosynthesis begins. That's on every leaf, on every plant, including all the blades of grass. All over the world.
    ::阳光照到植物叶子的每一秒,光合作用的过程就开始。 每一个叶子上,每一个植物上, 包括所有的草叶上, 全世界。

    Photosynthesis: The Most Important Chemical Reaction for Life on Earth
    ::光合作合:地球上生命最重要的化学反应

    What do pizza, campfires, dolphins, automobiles, and glaciers have in common? In the following section, you'll learn that all five rely on photosynthesis, some in more ways than one. Photosynthesis is often considered the most important chemical reaction for life on earth. Let's delve into how this process works and why we are so indebted to it.
    ::披萨、营火、海豚、汽车和冰川有什么共同之处?在下一节,你会知道所有五人都依赖光合作用,有些在不止一种方式上。光合作用通常被认为是地球上生命中最重要的化学反应。让我们来探究一下这个过程是如何运作的,以及为什么我们如此感激它。

     

     

    Photosynthesis involves a complex series of chemical reactions, each of which convert one substance to another. These reactions taken as a whole can be summarized in a single symbolic representation – as shown in the chemical equation below.
    ::光合作用涉及一系列复杂的化学反应,其中每种反应都将一种物质转换为另一种物质。 这些反应作为一个整体可以用一个符号来概括 — — 如下文化学方程式所示。

    We can substitute words for the chemical symbols. Then the equation appears as below.
    ::我们可以用词代替化学符号,然后方程式出现如下。

    Like all chemical equations, this equation for photosynthesis shows reactants connected by plus signs on the left and products, also connected by plus signs, on the right. An arrow indicating the process or chemical change leads from the reactants to the products, and conditions necessary for the chemical reaction are written above the arrow. Note that the same kinds of atoms, and number of atoms, are found on both sides of the equation, but the kinds of compounds they form change.
    ::和所有化学方程式一样,光合作用方程式显示左侧和右侧产品上与附加符号相连的反动物。箭头显示过程或化学变化从反应物到产品的导线,化学反应的必要条件写在箭头上方。请注意,在方程式两侧都发现了同样的原子和原子数量,但是它们构成的化合物种类会发生变化。

    You use chemical reactions every time you cook or bake. You add together ingredients (the reactants), place them in specific conditions (often heat), and enjoy the results (the products). A recipe for chocolate chip cookies written in chemical equation form is shown below.
    ::每次做饭或烘烤时都使用化学反应。将成分(反应剂)加在一起,将其置于特定条件下(经常加热),并享受结果(产品)。下面以化学方程形式写成的巧克力曲奇饼食谱。

    Compare this familiar recipe to photosynthesis below.
    ::比较这个熟悉的食谱与下面的光合作用。

    The equation shows that the “ingredients” for photosynthesis are carbon dioxide, , and light energy . Plants, , and photosynthetic take in light from the sun, molecules of carbon dioxide from the air, and water molecules from their environment and combine these reactants to produce food (glucose).
    ::该等式表明光合作用“元素”是二氧化碳和光能。 植物和光合用光从太阳中提取光,空气中的二氧化碳分子,环境中的水分子,这些反应剂结合以生产食物(葡萄糖 ) 。 植物和光合用光从太阳中提取光,空气中的二氧化碳分子,环境中的水分子,以及这些反应剂生产食物(葡萄糖)的结合。

    Of course, light, carbon dioxide, and water mix in the air even without plants. But they do not chemically change to make food without very specific necessary conditions which are found only in the of photosynthetic organisms . Necessary conditions include:
    ::当然,光、二氧化碳和空气中的水混合,即使没有植物。 但它们不会化学改变,在没有非常具体的必要条件的情况下生产食物,这些条件只能在光合生物体内找到。 必要的条件包括:

    1. - which speed up chemical reactions
      ::- 加速化学反应
    2. chlorophyll - a pigment within plant cells which absorbs light
      ::叶绿素 -- -- 吸收光光的植物细胞中的色素
    3. - whose membranes embed chlorophyll, accessory pigments, and enzymes in patterns which maximize photosynthesis
      ::- 其膜嵌入叶绿素、附属色素和酶,以尽量增加光合作用模式

    Within plant cells or algal cells, chloroplasts organize the enzymes, chlorophyll, and accessory pigment molecules necessary for photosynthesis.
    ::在植物细胞或藻类细胞中,叶绿板组织光合作用所需的酶、叶绿素和附属色素分子。

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    Within plant cells or algal cells, chloroplasts organize the enzymes, chlorophyll, and accessory pigment molecules necessary for photosynthesis.
    ::在植物细胞或藻类细胞中,叶绿板组织光合作用所需的酶、叶绿素和附属色素分子。

    When the reactants meet inside chloroplasts, or the very similar cells of blue-green bacteria, chemical reactions combine them to form two products: energy-rich glucose molecules and molecules of oxygen gas. Photosynthetic organisms store the glucose (usually as starch) and release the oxygen gas into the atmosphere as waste.
    ::当反应物在叶板内或非常相似的蓝绿色细菌细胞内相遇时,化学反应会把它们结合成两种产品:富能量的葡萄糖分子和氧气分子。光合成生物将葡萄糖(通常作为淀粉)储存起来,并将氧气作为废物释放到大气中。

    Let's review the chemical equation for photosynthesis once more, this time at the level of atoms as in the equation below.
    ::让我们再审查一次光合作用化学方程式, 这次在原子一级, 如以下方程式一样。

    Look closely at its primary purpose: storing energy in the chemical bonds of food molecules. The source of energy for food is sunlight energy. The source of carbon atoms for the food molecules is carbon dioxide from the air, and the source of hydrogen atoms is water. Inside the cells of plants, algae, and photosynthetic bacteria, chlorophyll, and enzymes use the light energy to rearrange the atoms of the reactants to form the products, molecules of glucose and oxygen gas. Light energy is thus transformed into chemical energy, stored in the bonds which bind six atoms each of carbon and oxygen to twelve atoms of hydrogen – forming a molecule of glucose. This energy rich molecule becomes food for the plants, algae, and bacteria themselves as well as for the heterotrophs which feed on them.
    ::仔细看看它的首要目的:将能源储存在食物分子的化学链条中。食物的能源来源是阳光能源。食物分子的碳原子来源是空气中的二氧化碳,氢原子来源是水。 在植物、藻类和光合细菌、叶绿素和酶的细胞中,光能用来重新排列反应器的原子以形成产品、葡萄糖分子和氧气。 因此,光能变成了化学能源,储存在将碳和氧的6个原子分别结合到氢的12个原子 — — 形成葡萄糖的分子。 这种丰富的能量分子成为植物、藻类和细菌本身的食品,以及它们所养生的血化营养的食品。

    One last detail: why do “6”s precede the CO 2 , H 2 O, and O 2 ? Look carefully, and you will see that this “balances” the equation: the numbers of each kind of atom on each side of the arrow are equal. Six molecules each of CO 2 and H 2 O make 1 molecule of glucose and 6 molecules of oxygen gas.
    ::最后一个细节:为什么“6”先于CO2、H2O和O2?仔细看,你会看到这个“平衡”方程式:箭头两侧每种原子的数量相等。每个CO2和H2O的6个分子产生一个葡萄糖分子和氧气的6个分子。

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    The two stages of photosynthesis are the light reactions and the Calvin cycle. Do you see how the two stages are related?
    ::光合作用的两个阶段是光反应和卡尔文循环。你看到这两个阶段之间的关系吗?

    Historical Perspective
    ::历史视角

    Life requires photosynthesis for fuel and for the oxygen to burn that fuel. Since the Industrial Revolution (late 18th and early 19th centuries), we humans have relied on products of ancient photosynthesis for enormous quantities of fossil fuel energy. And, knowingly or not, we have also benefited from photosynthesis to remove the carbon dioxide produced when we burn those fuels. So it may not surprise you that biologists have studied this critical process in great detail.
    ::生命需要光合作用燃料和氧来燃烧燃料。 自工业革命(18世纪末和19世纪初)以来,人类依靠古代光合作用产品来获取大量化石燃料能源。 而且,不管是否知情,我们也从光合作用中受益,以去除燃烧这些燃料时产生的二氧化碳。因此,生物学家们非常详细地研究了这一关键过程,这并不奇怪。

    Although photosynthesis may seem straightforward in this form, such simplicity is deceiving for two reasons. First, the photosynthesis equation summarizes dozens of individual chemical reactions involving many intermediate compounds. And second, just discovering major players like CO 2 and O 2 was challenging, because our ordinary cannot detect these molecules in “thin air!”
    ::尽管光合作用在这种形式上可能看起来直截了当,但这种简单化是欺骗性的,原因有二。 首先,光合作用方程式总结了涉及许多中间化合物的数十种化学反应。 其次,仅仅发现二氧化碳和氧等主要玩家是具有挑战性的,因为我们的普通人无法在“深空气”中检测到这些分子。

    How do we know that the chemical reaction in photosynthesis really happens? Two famous historical help us begin to understand this process. In the 17 th century, people who thought about it at all assumed that plants get their food from the soil . Many people, encouraged by sellers of “plant food,” still do. In 1638, Jan Baptist Van Helmont planted a 5 pound willow tree, like the one shown in  Figure , in a 200 pound tub of soil. After 5 years of watering the plant, he weighed both again. The willow had gained over 160 pounds, but the soil had lost only 2 ounces. Van Helmont concluded that plants do not get their materials from soil, and inferred that they grow using materials from water (which he did not measure). As you know now, he was half right. Although soil provides important nutrients to plants, it supplies neither the energy nor the vast majority of the materials to build the plant. We must excuse him, because no one in the 17 th century knew that carbon atoms form the basis of life, or that they float around in air in the form of carbon dioxide.
    ::我们怎么知道光合作用化学反应真的会发生?两个著名的历史学家帮助我们开始理解这个过程。在17世纪,那些想到它的人认为植物从土壤中获取食物。许多人在“植物食品”销售者的鼓励下仍然这样做。1638年,Jan Baptister Van Helmont在一块200磅的土壤浴缸里种植了一棵5磅的柳树,就像图中显示的那棵那样。在给植物浇水5年之后,他又把两者都重了起来。柳树增加了160磅以上,但土壤却只损失了2盎司。Van Helmont认为植物不能从土壤中获取原料,并推断植物是用水(他没有测量到的)材料种植的。现在,他是一半的权利。虽然土壤为植物提供了重要的营养,但它没有提供能量和绝大多数材料来建造植物。我们必须原谅他,因为17世纪没有人知道碳原子是生命的基础,或者它们以二氧化碳的形式在空气中漂浮。

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    In the 17 th century, Jan Van Helmont, a Flemish chemist, physiologist, and physician, weighed and potted a willow tree, showing that plants do not get food from the soil.
    ::17世纪,佛兰德化学学家、生理学家和医生Jan Van Helmont 体重过重,栽种了一棵柳树,表明植物不能从土壤中获取食物。

    In the late 1770s, minister and natural philosopher Joseph Priestley burned a candle in a jar of air and observed that the candle burned out long before it ran out of wax. A similar experiment with a mouse resulted in the mouse's death. Priestley suggested that , like candles, “injure” the air. Adding a mint plant, as shown in Figure , however, “restored” the air which had been “injured” by the mouse or the candle. Only later, after many chemistry experiments, did Priestley publish his discovery of “dephlogisticated air.” But in his studies of mice, plants, and candles, he had shown that plants produce, and animals consume, oxygen gas.
    ::1770年代末期,牧师和自然哲学家约瑟夫·皮斯利(Joseph Pistricley)用一罐空气烧毁了一根蜡烛,并观察到蜡烛在蜡光用完之前很久就烧光了。 一项类似的老鼠实验也导致老鼠死亡。 皮斯利建议,像蜡烛一样,“在空气中”“继续”活动。 然而,如图所示,添加了一座薄荷植物,“恢复”了被老鼠或蜡烛“伤害”的空气。 只是在后来,经过许多化学实验之后,皮斯利才公布了他发现的“脱节空气 ” 。 但是,在对老鼠、植物和蜡烛的研究中,他已经表明,植物生产了氧气,动物消耗了氧气。

    Joseph Priestly's bell jar experiment

    Joseph Priestly's bell jar experiment.
    ::约瑟夫·皮斯利的铃罐实验

    During the 20 th century, scientists learned that photosynthesis involves much more than just the three reactants, the three necessary conditions, and the two products shown in the equation. Using powerful microscopes, scientists narrowed the process to one type of organelle within the plant – the chloroplast.
    ::在20世纪,科学家们了解到光合作用涉及的远不止三个反应体、三个必要条件以及方程式中显示的两种产品。 科学家们利用强大的显微镜将过程缩小到工厂内的一种有机体 — — 即叶片。

    Summary
    ::摘要

    • The photosynthesis chemical equation states that the reactants (carbon dioxide, water and sunlight), yield two products, glucose and oxygen gas.
      ::光合作用化学方程式指出,反应物(二氧化碳、水和阳光)产生两种产品,即葡萄糖和氧气。
    • The single chemical equation represents the overall process of photosynthesis. It also summarizes many individual chemical reactions that were understood only after hundreds of years of scientific exploration.
      ::单一化学方程式代表了光合作用的总体过程,还概述了许多单项化学反应,这些反应只是在经过数百年的科学探索后才理解的。
    • Chloroplasts are the organelles within plant and algal cells that organize enzymes and pigments so that the chemical reactions proceed efficiently.
      ::氯甲醚是植物和藻类细胞中的有机物,它们组织酶和颜料,使化学反应有效进行。
    • Chlorophyll is a pigment that absorbs sunlight energy.
      ::叶绿素是一种吸收阳光能量的色素。

    Review
    ::回顾

    1. Using symbols, write the overall chemical equation for photosynthesis, labeling the reactants, necessary conditions, and products.
      ::使用符号,为光合作用编写整个化学方程式,标注反应器、必要条件和产品。
    2. Summarize Jan Van Helmont's willow tree experiment. State his conclusion and the inference he made after his experiment, and explain how his data supports each. Finally, relate his findings to what we know today about the overall process of photosynthesis.
      ::总结Jan Van Helmont的柳树实验。 陈述他的结论和他实验后所作的推论,并解释他的数据如何支持每个实验。 最后,将他的研究结果与我们今天所了解的光合作用的总体过程联系起来。
    3. Using the overall equation for photosynthesis, explain which components relate to J.B. Priestley's observation that “Plants restore the air that animals injure.”
      ::使用光合作用的总方程式解释哪些成分与J.B. Priestley的观察有关,即“植物恢复了动物伤害的空气”。

    Explore More
    ::探索更多

    Use this resource to answer the questions that follow.
    ::使用此资源回答下面的问题 。

     

    1. What are the "raw materials" of photosynthesis? Where do these materials come from?
      ::光合作用“原始材料”是什么?这些材料来自何处?
    2. What are the products of photosynthesis? How are these products made?
      ::光合作用的产品是什么?这些产品是如何制造的?
    3. Where does photosynthesis occur?
      ::光合作用在哪里发生?
    4. What happens to the glucose molecules?
      ::葡萄糖分子会怎么样?