大学生物专业英语lesson-two.ppt

2023/9/30,Lesson Two Photosynthesis,2023/9/30,教学目的：使学生掌握细胞的光合作用机理，光合系统与光合系统结构与功能之间的关系。相关英语词汇以及主要用法。教学重点：光合作用中相关的概念和功能，及相关英语词汇的掌握 教学难点：专业英语词汇的记忆,2023/9/30,Photosynthesis n.光合作用Chlorophyll n.叶绿素Protist n.原生生物Exergonic a.放能的Endergonic a.吸能的Chloroplast n.叶绿体Thylakoid n.类囊体,Glossary,2023/9/30,Photosynthesis occurs only in the chlorophyll-containing cells of green plants,algae,and certain protists and bacteria.光合作用只发生在含有叶绿素的绿色植物细胞，藻类，某些原生生物和细菌之中。,Introduction,2023/9/30,Overall,it is a process that converts light energy into chemical energy that is stored in the form of molecular bonds.总体来说，这是一个将光能转化成化学能，并将能量贮存在分子键中。,2023/9/30,From the point of view of chemistry and energetics,it is the opposite of cellular respiration.从化学和热力学(动能学)角度来看，它是细胞呼吸作用的逆反应Whereas cellular respiration is highly exergonic and releases energy,photosynthesis requires energy and is highly endergonic.但是细胞呼吸作用是高度放能的，光合作用是需要能量的,并且是高度吸能的过程。,2023/9/30,Photosynthesis starts with CO2 and H2O as raw materials and proceeds through two sets of partial reactions.光合作用以二氧化碳和水为原材料并经历两步化学反应。In the first set,called the light-dependent reactions,water molecules are split(oxidized),O2 is released,and ATP and NADPH are formed.第一步，称光反应，水分子裂解（分解）(被氧化)，氧分子被释放，ATP和NADPH形成。These reactions must take place in the presence of light energy.此反应必须在存在光能的条件下发生。,2023/9/30,2023/9/30,In the second set,called light-independent reactions,CO2 is reduced(via the addition of H atoms)to carbohydrate.第二步，称暗反应，二氧化碳被还原成碳水化合物。These chemical events rely on the electron carrier NADPH and ATP generated by the first set of reactions.这步反应依赖于由第一步反应产生的电子载体NADPH以及ATP。,2023/9/30,2023/9/30,Both sets of reactions take place in chloroplasts.两步反应都发生在叶绿体中。Most of the enzymes and pigments for the light-dependent reactions are embedded in the thylakoid membrane of chloroplasts.光反应需要的大部分酶和色素都是包埋在叶绿体的类囊体膜上。The dark reactions take place in the stroma.暗反应发生在基质中。,2023/9/30,1.How light energy reaches photosynthetic cells光合细胞如何吸收光能的,2023/9/30,Glossaryabsorption spectrum：吸收光谱Carotenoid：类胡萝卜素Antenna：天线、触角Funnel：漏斗、烟窗Aggregation：集合体、聚合Photosystem：光系统,2023/9/30,The energy in light photons in the visible part of the spectrum can be captured by biological molecules to do constructive work.生物分子能捕获可见光谱中光子的能量。The pigment chlorophyll in plant cells absorbs photons within a particular absorption spectruma statement of the amount of light absorbed by chlorophyll at different wavelengths.植物细胞中的叶绿素可以吸收特定吸收光谱中的光子。,2023/9/30,When light is absorbed it alters the arrangement of electrons in the absorbing molecule.在吸收光能时,光可以改变捕光分子中的电子排列。The added energy of the photon boosts the energy condition of the molecule from a stable state to a less-stable excited state.光子的能量激活了分子的能量状态，使其从基态（稳定态）进入激发态（不稳定的）。,2023/9/30,During the light-dependent reactions of photosynthesis,as the absorbing molecule returns to the ground state,the“excess”excitation energy is transmitted to other molecular and stored as chemical energy.在光合作用的光反应中,当捕光分子回到基态时,额外的激发能被转移到其它分子中并且以化学能的形式贮存.,2023/9/30,All photosynthetic organisms contain various classes of chlorophylls and one or more carotenoid pigments that also contribute to photosynthesis.所有的光合生物都含有各种类型的叶绿素和一种或多种与光合作用相关的类胡萝卜素分子（光合作用的辅助色素）。Groups of pigment molecules called antenna complexes are present on thylakoids.天线色素分子群（称作天线复合体的色素分子群）存在于类囊体中。,2023/9/30,Light striking any one of the pigment molecules is funneled to a special chlorophyll a molecule,termed a reaction-center chlorophylls,which directly participates in photosynthesis。激活色素分子的光能象进入漏斗一样被转移到直接参与光合作用的反应中心叶绿素分子中。,2023/9/30,Most photosynthetic organisms possess two types of reaction-center chlorophylls,P680 and P700,each associated with an electron acceptor molecule and an electron donor molecule.大多数光合生物含有两个反应中心叶绿素分子，P680和P700，每个都与电子受体和电子供体相连。These aggregations are known respectively as photosystem I(P700)and photosystem II(P680).这些集合体分别是大家熟知的光系统和光系统。,2023/9/30,2.The light-dependent reaction:converting solar energy into chemical-bond energy光反应：太阳能转化成化学能,2023/9/30,Cleave v.裂开、劈开Plastiquinone n.质醌Ferredoxin n.生化铁氧化还原蛋白Coenzyme 辅酶Photophosphorylation 光合磷酸化noncyclic photophosphorylation 非环形光合磷酸化ribulose biphosphate 核酮糖二磷酸carboxylase n.羧(基)酶,羧化酶,2023/9/30,photorespiration n.生化光呼吸(作用)Anatomy n.剖析,解剖学arid adj.干旱的,贫瘠的(土地等),无趣的,沉闷的lessen v.减少,减轻,2023/9/30,The photosystems of the light-dependent reactions are responsible for the packaging of light energy in the chemical compounds ATP and NADPH.光反应的光系统将光能转化成化合物（化学复合物）ATP和NADPH。,2023/9/30,This packaging takes place through a series of oxidation-reduction reactions set in motion when light strikes the P680 reaction center in photosystem II.当光激活光系统的光反应中心时，该转化过程是通过一系列的氧化还原反应来实现的。（当光激活光系统的光反应中心时，通过一系列的氧化还原反应实现能量的传递(前一句中packaging，传递能量)。）,2023/9/30,In this initial event water molecules are cleaved,oxgen is released,and electrons are donated.反应开始时，水被分解，氧被释放并提供电子。These electrons are accepted first by plastiquinone and then by a series of carries as they descend an electron transport chain.电子沿着电子传递链,首先传递给质体醌，然后通过一系列载体。（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。）,2023/9/30,For each four electrons that pass down the chain,two ATPs are formed.每传递4个电子，形成2个ATP。The last acceptor in the chain is the P700 reaction center of photosystem I.电子传递链上的最后一个受体是光系统的反应中心。,2023/9/30,At this point incoming photons boost the energy of the electrons,and they are accepted by ferredoxin.此处光子激活电子，电子传递给铁氧还蛋白。Ferredoxin is then reoxidized,and the coenzyme NADP+is reduced to the NADPH.铁氧还蛋白再氧化，并且辅酶NADP+还原成NADPH。The ATP generated previously and the NADPH then take part in the light-independent reactions.先前（早期）产生的ATP和NADPH进入（然后参与）暗反应。,2023/9/30,The production of ATP from the transport of electrons excited by light energy down an electron transport chain is termed photophosphorylation.由电子传递链偶连（由光激发的）产生ATP的过程称为光合磷酸化。,2023/9/30,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 photosystem II and I.通过光合系统流经光合系统的电子路径称非循环式光合磷酸化；植物也可以通过循环式光合磷酸化获得额外的ATP，在循环式光合磷酸化过程中,一些电子在光系统和之间的电子传递链中回流。,2023/9/30,2023/9/30,3.The light-independent reactions:building carbohydrates暗反应：碳水化合物的形成,2023/9/30,In the light-independent reactions of photosynthesis,which are driven by ATP and NADPH,CO2 is converted to carbohydrate.由ATP和NADPH驱动的暗反应中，二氧化碳转化成碳水化合物。The reaction are also known as the Calvin-Benson cycle.该反应也就是卡尔文循环。,2023/9/30,2023/9/30,Atomspheric CO2 is fixed as it reacts with ribulose biphosphate(RuBP),a reaction that is catalyzed by the enzyme ribulose biphosphate carboxylase.在二磷酸核酮糖羧化酶催化下,二磷酸核酮糖(RuBP)与空气中的CO2反应,从而将二氧化碳固定。,2023/9/30,The reduction of CO2 to carbohydrate is completed via several more steps of the cycle.CO2 被还原成碳水化合物是通过卡尔文循环的其它若干反应来实现的。Finally,RuBP is regenerated so that the cycle may continue.最后,RuBP再生,该循环从而得以继续。,2023/9/30,4.Oxygen:An inhibition of photosynthesis氧气：光合作用的抑制剂,2023/9/30,High levels of oxygen in plant cells can disrupt photosynthesis and can cause photorespiration an inefficient form of the dark reactions in which O2 is fixed rather than CO2 and no carbohydrate is produced.植物细胞中的高水平的氧气分子可以阻断光合作用,引起光呼吸,在光呼吸中,固定的是O2而不是CO2,并且没有碳水化合物的形成。,2023/9/30,5.Reprieve from photorespiration:the C4 pathway 减缓光呼吸:C4 途径,2023/9/30,Most plants are C3 plant;they experience decreased carbohydrate production under hot,dry conditions as a result of the effects of photorespiration.大多数植物是碳3植物;在高温干旱条件下，由于光呼吸作用的影响,碳水化合物产量降低。,2023/9/30,Among C4 plants,however,special leaf anatomy and a unique biochemical pathway enable the plant to thrive in arid conditions.而在碳4植物中，由于叶片的特殊结构和独特的化学路径使植物在干旱的条件下依然很茂盛。,2023/9/30,Thus C4 plants lessen photorespiration by carrying out photosynthesis only in cells that are insulated from high levels of CO2.碳4植物通过仅仅在与高浓度的CO2隔离的细胞中进行光合作用来减轻光呼吸。They also possess a novel mechanism for carbon fixation.C4植物也有一个碳固定的新机制。,2023/9/30,2023/9/30,！,