光合作用_综合百科

光合作用(photosynthesis)

绿色植物和某些特定生物体吸收光能并将其转变为化学能的过程。在绿色植物中，叶子中叶绿体所含的叶绿素吸取光能，并将水、二氧化碳和矿物质转变成氧气和富含能量的有机化合物（简单和复杂的醣类），该有机化合物为构成植物和动物生命形式的基础。光合作用由一系列的光化学反应和反应组成。光合作用分为两阶段。在依赖光照反应的阶段（光阶段）期间，叶绿素吸收的光能将色素分子中的某些电子激发到更高能阶，这些电子离开叶绿素并经过一系列的分子，释出能量形成NADPH（的一种）和高能量的三磷酸腺。做为光合作用副产物的氧气，由叶片的毛细孔释出至大气层中。NADPH和三磷酸腺则进行第二阶段不需要光线的暗反应（或卡尔文循环，由卡尔文所发现）。在暗反应中利用大气中的二氧化碳生成葡萄糖。光合作用对维持地球上的生命是相当重要的，若是停止了光合作用，很快的地球上将只有少数食物和有机物质存在，而几乎大部分的生命都会消失。

English version：

photosynthesis

Process by which green plants and certain other organisms transform light into chemical energy. In green plants, light energy is captured by chlorophyll in the chloroplasts of the leaves and used to convert water, carbon dioxide, and minerals into oxygen and energy-rich organic compounds (simple and complex sugars) that are the basis of both plant and animal life. Photosynthesis consists of a number of photochemical and enzymatic reactions. It occurs in two stages. During the light-dependent stage (light reaction), chlorophyll absorbs light energy, which excites some electrons in the pigment molecules to higher energy levels; these leave the chlorophyll and pass along a series of molecules, generating formation of NADPH (an enzyme) and high-energy ATP molecules. Oxygen, released as a by-product, passes into the atmosphere through pores in the leaves. NADPH and ATP drive the second stage, the dark reaction (or Calvin cycle, discovered by Melvin Calvin), which does not require light. During this stage glucose is generated using atmospheric carbon dioxide. Photosynthesis is crucial for maintaining life on earth; if it ceased, there would soon be little food or other organic matter on the planet, and most organisms would disappear.

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