📚 The Light-Dependent Reactions of Photosynthesis | 光合作用的光依赖反应
The light-dependent reactions are the first phase of photosynthesis, taking place in the thylakoid membranes of chloroplasts. They harness light energy to produce ATP and reduced NADP (NADPH), simultaneously generating oxygen gas. These products are essential for the Calvin cycle, which synthesises sugars from carbon dioxide.
光依赖反应是光合作用的第一阶段，发生在叶绿体的类囊体膜上。它们利用光能生成ATP和还原型NADP（NADPH），同时产生氧气。这些产物是卡尔文循环从二氧化碳合成糖类所必需的。
1. Overview of the Light-Dependent Reactions | 光依赖反应概述
The light-dependent reactions convert radiant energy into chemical energy. They require light, water, NADP⁺ and ADP + Pᵢ. The overall outcomes are the production of ATP, NADPH and O₂. These reactions are called 'light-dependent' because they directly depend on light absorption by photosynthetic pigments.
光依赖反应将辐射能转化为化学能。它们需要光、水、NADP⁺以及ADP+磷酸根。总产物是ATP、NADPH和氧气。这些反应称为“光依赖”是因为它们直接依赖于光合色素对光的吸收。
There are two pathways: non-cyclic photophosphorylation, which yields ATP, NADPH and O₂, and cyclic photophosphorylation, which generates only ATP.
存在两种途径：非循环光磷酸化，产生ATP、NADPH和O₂；以及循环光磷酸化，只产生ATP。
2. The Thylakoid Membrane: Site of the Reactions | 类囊体膜：反应的场所
The reactions occur across the thylakoid membrane, a phospholipid bilayer found inside chloroplasts. The membrane is folded into stacked grana and unstacked stroma lamellae, providing a large surface area. Embedded within this membrane are photosystems, electron carriers, and ATP synthase complexes.
反应发生在类囊体膜上，这是一种位于叶绿体内部的磷脂双分子层。膜折叠成堆叠的基粒和非堆叠的基质片层，提供大的表面积。膜中嵌有光系统、电子传递体和ATP合酶复合物。
The membrane separates the stroma from the thylakoid lumen. During electron transport, protons (H⁺) are pumped into the lumen, creating a proton gradient that drives ATP synthesis.
该膜将基质与类囊体腔分隔开。在电子传递过程中，质子（H⁺）被泵入腔中，形成质子梯度，驱动ATP合成。
3. Photosystems: Capturing Light Energy | 光系统：捕获光能
Two photosystems, Photosystem II (PSII) and Photosystem I (PSI), work in series during non-cyclic photophosphorylation. Each photosystem consists of a light-harvesting complex (antenna complex) containing chlorophyll a, chlorophyll b, and carotenoids, and a reaction centre. PSII's reaction centre contains P680, while PSI's contains P700.
两个光系统，光系统II（PSII）和光系统I（PSI），在非循环光磷酸化中串联工作。每个光系统由集光复合体（天线复合体）和反应中心组成，集光复合体含叶绿素a、叶绿素b和类胡萝卜素。PSII的反应中心含P680，PSI的反应中心含P700。
When a pigment molecule absorbs a photon, its energy is transferred to the reaction centre, raising an electron to a higher energy level. The excited electron is then passed to an electron acceptor, initiating electron flow.
当色素分子吸收光子，能量传递至反应中心，将一个电子提升到更高能级。受激发的电子随后传递给电子受体，启动电子流动。
4. Non-Cyclic Photophosphorylation: The Z-Scheme | 非循环光磷酸化：Z方案
Non-cyclic photophosphorylation involves both photosystems and follows a 'Z-scheme' shape in terms of energy level changes. Water is the initial electron donor; NADP⁺ is the final electron acceptor. The process generates ATP and NADPH while releasing O₂.
非循环光磷酸化涉及两个光系统，其能级变化呈“Z方案”形状。水是初始电子供体；NADP⁺是最终电子受体。该过程产生ATP和NADPH并释放氧气。
The key
Published by TutorHao | A-Level Biology Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
或截图后用「扫一扫 → 相册」选择本图