光反应 - 高级

Oxygen has been described as a "waste product." How is this possible?
::氧气被描述为“废物产品”。这怎么可能呢?

You could argue that oxygen is one of the most important, if not THE most important molecule necessary for life. However, oxygen is essentially just a waste product of the of photosynthesis. It is a "leftover" from a necessary part of the process. All the oxygen that is necessary to maintain most forms of life just happens to be released from the plant during this process.
::你可以争辩说,氧是生命中最重要的分子之一,即使不是最重要的分子。然而,氧基本上只是光合作用产生的废物。它是过程一个必要部分的“剩余部分 ” 。 保持大多数生命形式所需要的全部氧正是在这一过程中从工厂中释放出来的。

Photosynthesis Stage I: The Light Reactions: Chloroplasts Capture Sunlight Chemical Energy…
::光合作用第一阶段:光反应:氯捕获阳光光化能...

Every second, the sun fuses over 600 million tons of hydrogen into 596 tons of helium, converting over 4 tons of helium (4.3 billion kg) into light and heat energy . Countless tiny packets of that light energy travel 93 million miles (150 million km) through space, and about 1% of the light which reaches the Earth's surface participates in photosynthesis. Sunlight is the source of energy for photosynthesis, and the first set of reactions which begin the process requires light – thus the name, "Light Reactions", or Light-dependent Reactions. This light is absorbed by chlorophyll in the thylakoid membrane of in the plant .
::每秒,太阳将超过6亿吨的氢结合成596吨的氦,将超过4吨的(43亿公斤)转化为光和热能。 光能的无数小袋通过空间飘移9300万英里(15 000万公里),而到达地球表面的大约1 % 的光线也参与光合作。 阳光是光合作的能量源,而开始这一过程的第一组反应需要光光线 — — 也就是“光反应 ” ( Light Reactions ) , 或光依赖光的反应。 这一光线被植物中胸膜中的叶绿素吸收。

The pigment molecule chlorophyll of leaf cells appears green because its electrons absorb blue-violet and red light and reflect green, orange, and yellow light. There are actually several different kinds of chlorophyll (a,b, and d) in plants. Each kind of pigment absorbs specific wavelengths (colors) of light. Sunlight contains many different wavelengths, which you see when they separate into a rainbow. Not all colors of light are used in photosynthesis. Most plants, , and photosynthetic appear green because they reflect green wavelengths. Their pigments have absorbed the violet-blue and red wavelengths. The amount of photosynthesis depends on the wavelength of light available. Cartenoids are also pigments that absorb sunlight.
::叶细胞的色素分子叶绿素看起来是绿色的, 因为它的电子吸收了蓝色紫罗兰和红光, 反映了绿色、 橙色和黄色的光。 实际上植物中存在几种不同的叶绿素(a、b和d) 。 每一种色素吸收了特定的波长( 彩色) 。 太阳光包含许多不同的波长, 当它们分离成彩虹时你可以看到这些波长。 光合作用并不是所有光的颜色都使用光。 大多数植物、 和光合体都是绿色的, 因为它们反映了绿色的波长。 它们的色素吸收了紫紫蓝色和红色波长。 光合作用量取决于光的波长。 素类也是吸收阳光的色。

When light strikes chlorophyll (or an accessory pigment) within the chloroplast, the energy is absorbed and transferred to electrons in the chlorophyll. Essentially, sunlight energizes or "excites," electrons within the chlorophyll molecule. Photosystem II is also known as P680, with P standing for pigment and 680 referring to the absorption maximum in the red part of the visible spectrum (680 nm). The primary electron donor in P680 receives excitation energy by absorbing a photon of light. These excited electrons jump up to higher energy levels and enter the electron transport chain ; they have absorbed or captured, and now carry, that energy. These high energy electrons are holding the energy that will be be transferred to glucose . In essence, these high energy electrons are holding the energy needed to support life.
::当叶绿板内的光点击中叶绿素(或附属色素)时,能量被吸收并转移到叶绿素中的电子中。基本上,光电或“电源”是叶绿素分子中的电子。光系统二也称为P680,P站着色素,P站着色素,680指可见光谱红部分的吸收最大值(680纳米)。P680中的主要电子捐献者通过吸收光子获得振动能量。这些兴奋电子跳到更高的能量水平,进入电子运输链中;它们吸收或捕捉了能量,现在携带了能量。这些高能量电子掌握着能量,这些能量将转移到葡萄糖中。实质上,这些高能量电子掌握着支撑生命所需的能量。

...And Change the Rules of Chemistry for Life!
::改变生命化学规则!

The excited electrons leave chlorophyll to participate in further reactions, leaving the chlorophyll “at a loss”; eventually they must be replaced. That replacement process also requires light, working with an complex to split molecules. In this process of photolysis (“splitting by light”), H ₂ O molecules are broken into hydrogen ions , electrons, and oxygen atoms. The electrons replace those originally lost from chlorophyll. Hydrogen ions and the high-energy electrons from chlorophyll will carry on the energy transformation drama after the Light Reactions are over.
::兴奋电子离开叶绿素以参与进一步反应,使叶绿素“丢失”;最终必须替换它们。替换过程还需要光线,与一个复合体合作分裂分子。在这一光解过程(“光分解 ” ) 中,H2O分子被破碎成氢离子、电子和氧原子。电子将取代最初从叶绿素中损失的。叶绿素中的氢离子和高能电子将在光反应结束后继续进行能源转化。

The oxygen atoms, however, form oxygen gas, which is a waste product of photosynthesis ( Figure ). The oxygen given off supplies most of the oxygen in our atmosphere . Before photosynthesis evolved, Earth's atmosphere lacked oxygen altogether, and this highly reactive gas was toxic to the many organisms living at the time. Something had to change! Most contemporary organisms rely on oxygen for efficient respiration . So plants don't just “restore” the air, as Joseph Priestley suggested. They also had a major role in creating it!
::然而,氧原子形成氧气,这是光合作用产生的废气(图 ) 。 我们大气中大部分氧气都是从氧气中释放出来的。 在光合作用演变之前,地球的大气层完全缺乏氧气,而这种高度反应性气体对当时生活的许多生物有毒。必须改变一些东西!大多数当代生物依靠氧来有效呼吸。因此,植物不能像约瑟夫·皮斯利所建议的那样“恢复”空气。它们在创造空气方面也起着重要作用。

To summarize, chloroplasts “capture” sunlight energy in two ways. Light “excites” electrons in pigment molecules, and light provides the energy to split water molecules, providing more electrons as well as hydrogen ions.
::简言之,叶绿石以两种方式“捕捉”阳光能量。 色素分子中的光“刺激”电子和光能为分解水分子提供了能量,提供了更多的电子和氢离子。

Now let's follow those excited electrons…
::现在让我们跟着那些激动人心的电子...

How Do Chloroplasts Convert Light Energy to Chemical Energy?
::氯甲醚如何将光能转化为化学能源?

Excited electrons which have absorbed light energy are unstable. However, the highly organized electron carrier molecules embedded in chloroplast membranes order the flow of these electrons, directing them through chains (ETCs). At each transfer, small amounts of energy released by the electrons are captured and put to work or stored. Some is also lost as heat with each transfer, but overall the light reactions are extremely efficient at capturing light energy and transforming it to chemical energy.
::吸收了光能的兴奋电子是不稳定的,然而,嵌入氯板膜中的高度有组织的电子载体分子命令这些电子流动,引导它们通过链条(ETCs)运行。在每次转移时,电子释放的少量能量被捕获并投入使用或储存。有些也随着每次转移的热量而丢失,但总体而言,光反应在捕捉光能并将其转化为化学能源方面极为高效。

Two sequential transport chains harvest the energy of excited electrons, as shown in Figure .
::如图所示,两条相继运输链收获兴奋电子的能量。

播放段落
1. First, starting with photosystem II, electrons pass down an ETC which captures their energy and uses it to pump hydrogen ions by into the thylakoids . These concentrated ions store potential energy by forming a chemiosmotic gradient or – a higher concentration of both positive charge and hydrogen inside the thylakoid than outside. The gradient formed by the H ⁺ ions is known as a chemiosmotic gradient. Picture this energy buildup of H ⁺ as a dam holding back a waterfall. Like water flowing through a hole in the dam, hydrogen ions “slide down” their concentration gradient through a which acts as both ion channel and enzyme. As they flow, the ion channel/enzyme ATP synthase uses their energy to chemically bond a phosphate group to ADP, making ATP .
   ::首先,从光系统II开始,电子传递出一种能捕捉其能量并将氢离子注入甲状腺的ETC。这些浓缩离子通过形成一种化学梯度或者 — — 在甲状腺内,正电荷和氢的浓度高于外部 — — 将潜在能量储存起来。H+离子形成的梯度被称为化学梯度。想象这种H+的能量积聚作为阻挡瀑布的水坝。就像流经大坝洞的水一样,氢离子“滑落 ” 其浓度梯度通过一个既作为离子通道又作为酶的电离子通道和酶。随着电离子通道/苯ATP合成酶的流动,它们利用电离子通道/苯乙烯合成酶的能量将磷酸酯组化学地连接到ADP,使ATP成为ATP。
播放段落
2. Light re-energizes the electrons in photosystem I, and they travel down a second electron transport chain (ETC), eventually bonding hydrogen ions to NADP ⁺ to form a more stable energy storage molecule, NADPH . NADPH is sometimes called “hot hydrogen,” and its energy and hydrogen atoms will be used to help build sugar in the second stage of photosynthesis. Whereas photosystem II has an absorption maximum at 680nm, photosystem I has an absorption maximum at 700nm, and is known as P700.
   ::光重新激活光电系统I的电子,它们沿着第二个电子运输链(ETC)运行,最终将氢离子连接到NADP+,形成一个更稳定的能源储存分子,NADPH。 NADPH有时被称为“热氢 ” , 其能量和氢原子将被用于帮助在光合作用第二阶段制造糖。 而光电系统II的吸收极限为680纳米,而光电系统I的吸收极限为700纳米,称为P700纳米。

NADPH and ATP molecules now store the energy from excited electrons – energy which was originally sunlight – in chemical bonds . Thus chloroplasts, with their orderly arrangement of pigments, enzymes, and electron transport chains, transform light energy into chemical energy. The first stage of photosynthesis – light-dependent reactions or simply “light reactions” – is complete.
::NADPH和ATP分子现在将兴奋电子 — — 最初是阳光的能源 — — 的能量储存在化学链中。 因此,叶片随着色素、酶和电子运输链的有序安排,将光能转化为化学能源。 光合作用的第一个阶段 — — 光依赖反应或简单的“轻微反应 ” — —是完整的。

Summary
::摘要

播放段落
• Light Reactions transform energy from sunlight into chemical energy, and produce and release oxygen gas.
  ::光反应将阳光能量转化为化学能源,产生和释放氧气。
播放段落
• Light also provides energy to split water molecules into electrons, hydrogen ions, and oxygen gas.
  ::光还提供能量,将水分子分裂成电子、氢离子和氧气。
播放段落
• The oxygen gas is released as “waste”, but it is the source of the oxygen in Earth's atmosphere.
  ::氧气作为“废物”释放,但它是地球大气中的氧源。
播放段落
• The captured energy is stored in the bonds of molecules, NADPH and ATP.
  ::所捕捉的能量储存在分子、NADPH和ATP的联结中。
播放段落
• Hydrogen ions are pumped into the thylakoids, forming an electrochemical gradient whose energy builds ATP molecules.
  ::氢离子被泵入胸腔,形成电化学梯度,其能量形成ATP分子。

Review
::回顾

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1. Summarize the events of the light reactions of photosynthesis.
   ::总结光合作用光反应的事件。
播放段落
2. What is photolysis and why is it important?
   ::什么是光解,为什么重要?
播放段落
3. Explain the role of the first electron transport chain in the formation of ATP during the light reactions of photosynthesis.
   ::解释第一个电子运输链在光合作用光反应时在ATP形成中的作用。
播放段落
4. Explain chemiosmosis.
   ::解释一下染色体
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5. What are the final products of the light reaction?
   ::光反应的最终产品是什么?