生物专业英语lesson-2-photosynthesis.ppt
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1、Lesson Two Photosynthesis,Warmingup Words and phrases Text Analysis Simple exercise Further references,Contents,人类对光合作用的科学研究至少已经进行了300多年,最近100年来与光合作用有关的研究已经获得了6次诺贝尔奖。时至今日,仍有许多问题需要探索。,Warmingup,Melvin Calvin, (1911-1997) Nobel Laureate, chemistry, 1961,Listen to a Photosynthesis Song and relax.,CO2H2
2、O C(H2O)nO2,光能,叶绿体,光合作用的总反应式:,光合作用是植物和藻类利用自身的叶绿素将可见光转化为能量(包括光反应和暗反应)驱动二氧化碳和水转化为有机物并释放氧气的过程。它是生物界赖以生存的生化反应过程 。,光合作用概图,类囊体,叶绿素a,H2O,1.第一阶段在叶绿体的哪一部位完成的? 2.第一阶段必有的外界条件是什么? 3. 第一阶段原料有哪些? 4. 第一阶段包括哪些步骤?产物有哪些?,第一阶段,类囊体,叶绿素a,ADP+Pi,ATP,H2O,NADPH,NADP+,H+,第一阶段是吸收光能,光解水,释放O2并形成高能量的ATP和NADPH,即将光能转化为活跃的化学能。此过程在
3、类囊体进行,同时需要光光反应,第一阶段,三碳化合物,CO2,多种酶 参与,固定,五碳化合物,(CH2O)n,NADPH,ATP,第二阶段,1.第二阶段在叶绿体的哪一部位完成的? 2.第二阶段必须有光吗? 3. 第二阶段原料有哪些? 4. 第二阶段包括哪些步骤?产物有哪些?,基质,三碳化合物,CO2,多种酶 参与,固定,五碳化合物,(CH2O)n,NADPH,ATP,第二阶段,第二阶段利用光反应产生的ATP和NADPH,固定CO2,合成糖,以稳定的化学能储存在糖中(卡尔文循环)。此过程发生在叶绿体基质中,无光也能完成暗反应,基质,也可将光合过程分为3大步骤: 1)原初反应:光能的吸收、传递和转换
4、为电能; 2)电子传递和光合磷酸化:电能转变为活跃的化学 3)碳同化:活跃的化学能再转变为稳定的化学能。,碳同化的途径 A)卡尔文循环(又叫C3途径):是最基本、最普遍的,且只有该途径才可以生成碳水化合物. B) C4途径(又叫Hatch-Slack途径) C)景天酸代谢途径(CAM). C4和CAM途径都是C3途径的辅助形式,只能起固定、运转、浓缩CO2的作用,单独不能形成淀粉等碳水化合物。,Glossary -about the photosynthesis The process of photosynthesis- about light-dependent reactions, li
5、ght-independent reactions, chlorophyll, photorespiration etc.,Focus in,1. Absorption spectrum bs:pn spektrm ,n.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.,Words and phrases,物质波谱及太阳光的光谱,6,
6、叶绿素的吸收波谱,光与叶绿体的相互作用,2. Calvin-Benson cycle,卡尔文-本森循环(又叫卡尔文循环、C3途径),卡尔文循环,C3循环中反应物及产物的生成,C3途径反应过程:羧化、还原和再生 A.羧化阶段:,RuBP,Rubisco(RuBP羧化酶),PGA(2分子) 酸能量低,不能贮存更多的能量,B.还原阶段:,PGA,DPGA,GAP (3-磷酸甘油醛),GAP是一种三碳糖,可以稳定的贮存能量,至此,消耗的光反应的ATP和NADPH,使光能转化为稳定的化学能,光合的贮能过程结束。,GAP的出路,叶绿体内,淀粉或葡萄糖(贮存形式),细胞质,蔗糖(运输形式),C.更新阶段:大
7、部分GAP经一系列转化,重新形成RuBP的阶段。,C3途径的总反应式可写成: 3CO2+5H2O+9ATP+6NADPHGAP+9ADP+8Pi+6NADP+ +3H+,3. carotenoid,n.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., krtnid ,辅助色素(accessory pigment
8、):叶绿体中的类胡萝卜素含有两种色素,即胡萝卜素(carotene)和叶黄素(lutein) 。功能为吸收和传递光能,是对叶绿素捕获光能的补充 。,连续双峰400-500nm,两个吸收峰 430-450nm蓝紫光区 640-660nm红光区,4. Chlorophyll kl:rfil ,n.叶绿素,The green substance of plants by which photosynthesis is accomplished; it is usually localized in intracellular organelles called chloroplasts.,主要有叶绿
9、素a(呈蓝绿色)和叶绿素b(呈黄绿色),叶绿体中叶绿素的分布,5. Chloroplast kl(:)rpl:st ,n.叶绿体,A plastid in which photosynthesis is carried out. Chloroplasts occur in all photosynthetic organisms except photosynthetic bacteria and blue-green algae.,叶绿体的形态与分布,叶绿体的结构 1 双层膜:内膜为选择性屏障。 2 基质:CO2同化;淀粉形成 3 基粒:由类囊体垛叠而成的绿色颗粒。,6. photophos
10、phorylation,n. 光合磷酸化作用,The synthesis of ATP from phosphate and ADP during photosynthesis, using light energy., ,futufsfrilein ,叶绿体在光下把无机磷酸和ADP转化为ATP,形成高能磷酸键的过程。,光合磷酸化的方式,7. Cyclic photophosphorylation,n. 环形光合磷酸化作用,Cyclic photophosphorylation is coupled to cyclicelectron flow, in which ATP is the onl
11、y product., ,futufsfrilein ,环式光合磷酸化: 从PS产生的电子,经过Fd和细胞色素b6/f等后,引起了ATP的形成,降低能位,又经PC回到原来的起点P700,形成闭合回路。,8. Noncyclic photophosphorylation,n. 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.,非环式光合磷酸化: PS所产生的
12、电子经过一系列的传递,在细胞色素复合体上引起ATP的形成,继而将电子传至PS,提高能位,最后用去还原NADP+。这样,电子经PS传出后不再返回。,9. C3 plant,A plant in which the light-independent reactions of photosynthesis start with a three-carbon compound. Most plants are C3 plants.,n.三碳植物,Melvin Calvin, (1911-1997) Nobel Laureate, chemistry, 1961,C3循环,C3循环中反应物及产物的生成
13、,10. C4 plant,A plant such as corn in which the light-independent reactions of photosynthesis start with a four-carbon compound.,n. 四碳植物,CO2固定的最初产物为四碳化合物的途径。,具有C4途径的植物称为C4植物。只具有C3途径的植物称为C3植物。 在农作物中,只有玉米、高粱、甘蔗、黍和粟属于C4植物。而其它的农作物,如水稻、小麦、大豆都属于C3植物,大多数树木等也属于C3植物。,C4途径需经过两种光合细胞,即在叶肉细胞的细胞质中,由PEPC催化羧化反应,形成C
14、4二羧酸, C4二羧酸运至维管束鞘细胞脱羧,释放的CO2再由C3途径同化。,C4途径反应过程:羧化、转移脱羧和再生,A.羧化阶段:场所叶肉细胞质,PEPHCO3,PEP羧化酶,OAAHOPO32,磷酸烯醇式丙酮酸,草酰乙酸,最初CO2受体,最初产物 不稳定,易转化,B.转移脱羧阶段: 按脱羧酶分为三个类型 .NADP苹果酸酶型:,OAA,苹果酸,丙酮酸,酶,CO2,叶肉细胞,维管束鞘细胞,.NAD苹果酸酶型:,OAA,天冬氨酸,丙酮酸,酶,CO2,叶肉细胞,维管束鞘细胞,C3途径,.PEP羧激酶型:,OAA,天冬氨酸,PEP,CO2,叶肉细胞,维管束鞘细胞,C.再生阶段:场所叶肉细胞,丙酮酸,
15、PEP,ATP,AMP+2Pi,丙酮酸双激酶,AMP+ATP,2ADP,11. light-dependent reactions,n. 光反应,The first stage in photosynthesis, driven by light energy. Electrons that trap the suns energy pass the energy to high-energy carriers such as ATP or NADPH, where it is stored in chemical bonds.,12. light-independent reactions,
16、n. 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.,13. photon,n. 光子,A particle that has zero mass or charge and unit spin, the quantum of the electromagnetic fi
17、eld and carrier of the electromagnetic force., futn ,原始称呼是光量子(light quantum),其静止量为零,不带电荷 ,是电磁辐射的载体。当一个光子被分子吸收时,就有一个电子获得足够的能量从而从内轨道跃迁到外轨道,具有电子跃迁的分子就从基态变成了激发态。,14. photorespiration,n. 光呼吸,A light-dependent type of respiration that occurs in most photosynthesis plants and differs from normal( or dark )
18、 respiration., ,futu,resprein ,光呼吸是与光合作用随伴发生的吸收O2和释放CO2的过程。 整个途径要经过三种细胞器,即在叶绿体中合成乙醇酸,在过氧化体中氧化乙醇酸,在线粒体中释放CO2。由于光呼吸与光合作用两者的底物均起始于RuBP,且都受Rubisco催化,因此,两者的活性比率取决于CO2和O2的浓度比例。在O2和CO2并存的环境中,光呼吸是不可避免的。光呼吸释放的CO2可被光合再固定。,15. photosynthesis,n. 光合作用,The synthesis of organic compounds by reduction of carbon dio
19、xide using light energy absorbed by chlorophyll., ,futusinsis ,16. photosystem,n. 光系统,One of the clusters of light-trapping pigments embedded in photosynthetic membranes. Photosystem I operates during the cyclic pathway; photosystem II operates during both the cyclic and noncyclic pathways., ,futsis
20、tm ,17. Ribulose biphosphate( RuBP),n. 核酮糖二磷酸,A compound with a backbone(主链) of five carbon atoms that is required for carbon fixation in the Calvin-Benson cycle of photosynthesis.,18. thylakoid,n. 类囊体,One of a number of flattened fluid-filled sacs that form the photosynthetic lamellar system of chl
21、oroplasts, photosynthetic bacteria, and blue-green algae, ail,kid ,Review the former content:,1. Absorption spectrum bs:pn spektrm ,2. Calvin-Benson cycle,3. carotenoid,4. Chlorophyll kl:rfil ,5. Chloroplast kl(:)rpl:st ,6. Cyclic photophosphorylation,7. C3 plant,8. C4 plant, krtnid ,9. light-depend
22、ent reactions,10. light-independent reactions,11. Noncyclic photophosphorylation,12. photon,13. photophosphorylation,14. photorespiration,15. photosynthesis,16. photosystem,17. Ribulose biphosphate( RuBP),18. thylakoid, futn , ail,kid , ,futusinsis ., ,futu,respirein .,How light energy reaches photo
23、synthetic cells? The light-dependent reactions: Converting solar energy into chemical bond energy The light-independent reactions: Building carbohydrates Oxygen: An inhibitor of photosynthesis Reprieve from photorespiration: The C4 pathway,Text Analysis,Questions & Answers,What process do you think
24、the photosynthesis is?,What benefit do you think plant can gain through photosynthesis?,Photosynthesis occurs only in the chlorophyll-containing cells of green plants, algae, and certain protists and bacteria. Overall, it is a process that converts light energy into chemical energy that is stored in
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