电子。电子首先传递给质体醌，然后通过一系列载体形成的电子传递链。每传递4个电子，形成2个ATP。最后一个受体存在于光反应系统Ⅰ的反应中心里。此处光子激活电子，电子传

+

递给铁氧还蛋白。铁氧还蛋白再氧化，并且辅酶NADP还原成NADPH。早期产生的ATP和NADPH进入暗反应。

The production of ATP from the transport of electrons excited by light energy down an electron transport chain is termed photophosphorylation. The one-way flow of electrons through photosystems II and I is called noncyclic photophosphorylation; plants also derive additional ATP through cyclic photophosphorylation, in which some electrons are shunted back through the electron transport chain between photosystems Ⅱ and Ⅰ.

由电子传递链偶连产生ATP的过程称为光合磷酸化。通过光合系统Ⅱ流经光合系统Ⅰ的电子路径称非循环式光合磷酸化；植物通过循环式光合磷酸化获得额外的ATP，一些电子在光合系统Ⅰ和Ⅱ之间的电子传递链中回流。

The Light-Independent Reactions: Building Carbohydrates 暗反应：碳水化合物的形成

In the light-independent reactions of photosynthesis, which are driven by ATP and NADPH, C02 is converted to carbohydrate. The reactions are also known as the Calvin-Benson cycle. Atmospheric CO2, is fixed as it reacts with ribulose biphosphate (RuBP), a reaction that is catalyzed by the enzyme ribulose biphosphate carboxylase. The reduction Of C02 to carbohydrate (fructose diphosphate) is completed via several more steps of the cycle. Finally, RUBP is regenerated so that the cycle may continue.

由ATP和NADPH驱动的暗反应中，二氧化碳转化成碳水化合物。即卡尔文循环。二磷酸核酮糖固定二氧化碳，由二磷酸核酮糖羧化酶催化。

Oxygen: An Inhibitor of photosynthesis（氧：光合作用的抑制因子）

High levels of oxygen in plant cells can disrupt photosynthesis and can also cause photorespiration-an inefficient fun of the dark reactions in which 02 is fixed rather than C02 and no carbohydrate is produced.

Reprieve from Photorespiration: The C4 Pathway

Most plants are C3 plants; they experience decreased carbohydrate production under hot, dry conditions as a result of the effects of photorespiration. Among C4 plants, however, special leaf anatomy and a unique biochemical pathway enable the plant to thrive in and conditions. Thus C4 plants lessen photorespiration by carrying out photosynthesis only in cells that are insulated from high levels of CO2. They also possess a novel mechanism for carbon fixation.

大部分植物是碳3植物，在高温干旱条件下，由于光呼吸作用而使碳水化合物的合成降低。而在大多数的碳4植物中，由于叶脉的特殊构造和独特的化学路径使植物依然很茂盛。这是碳固定的一个新机制。

课后作业：第一篇阅读材料 答案：1B,2A,3A,4D,5C,6c

Glossar

light-dependent reactions 光反应-

The first stage in photosynthesis, driven by light energy. Electrons that trap the sun's energy pass the energy to high-energy carriers such as ATP or NADPH, where it is stored in chemical bonds. light-independent reactions 暗反应

The second stage of photosynthesis, also called the Calvin-Benson cycle, which does not require light. During the six steps of the cycle, carbon is fixed and carbohydrates are formed. chloroplast 叶绿体

A plastid in which photosynthesis is carried out. Chloroplasts occur in all photosynthetic organisms except photosynthetic bacteria and blue-green algae. absorption spectrum 吸收光谱，吸收谱 The spectrum obtained when radiation (light, ultraviolet radiation, etc.) from a source giving a continuous spectrum is passed through a substance. Calvin-Benson cycle 卡尔文·本森循环

Cyclic reactions that are the \light-independent reactions of photosynthesis. In land plants, RUBP, or some other compound to which carbon has

been affixed, under goes rearrangements that lead to

formation of a sugar phosphate and to regeneration of the RUBP. The cycle runs on ATP and NADPH from light-dependent reactions. carotenoid 类胡萝卜素

Light-sensitive, accessory pigments that transfer absorbed energy to chlorophylls. They absorb violet and blue wave-lengths but transmit red, orange, and yellow.

chlorophyll 叶绿素

The green substance of plants by which

photosynthesis is accomplished; it is usually localized in intracellular organelles called chloroplasts. cyclic photophosphorylation 环形光合磷酸化（作用）

Cyclic photophosphorylation is coupled to cyclicelectron flow, in which ATP is the only product. C3 plant 三碳植物

A plant in which the light-independent reactions of photosynthesis start with a threecarbon compound. Most plants are C3 plants. C4 plant 四碳植物

A plant such as corn in which the light independent reactions of photosynthesis star with a four-carbon compound.

noncyclic photophosphorylation

非环形光合磷酸化作用

Noncyclic photophosphorylation is coupled to noncyclic electron flow, the electrons being used to reduce NADP+ as well as to make ATP. photon 光子

A particle that has zero mass or charge and unit spin, the quantum of the electromagnetic field and carrier of the electromagnetic force.

photophosphorylation 光合磷酸化作用

The synthesis of ATP from phosphate and ADP during photosynthesis, using light energy. photorespiration 光呼吸