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1、第六章 生物氧化电子传递 和氧化磷酸化作用,(Biological oxidation electron transport and oxidative phosphorylation),一、电子传递和氧化呼吸链 二、氧化磷酸化作用,Respiration and energy,One of the most complicated metabolic pathways encountered in biochemistry-the mitochondrial electron transport system and its related ATP synthase. Electron tr
2、ansferring via a chain of membrane bound carriers, across membrane proton gradient, ATP synthesis (with O2 consumed),Cells need energy to do all their work,To generate and maintain its highly ordered structure (biosynthesis of macromolecules). To generate all kinds of movement. To generate concentra
3、tion and electrical gradients across cell membranes. To maintain a body temperature. To generate light in some animals.,Some historical facts about our understanding on oxidative phosphorylation,1930s: Pyruvate was known to be completely oxidized to CO2 via the citric acid cycle (with O2 consumed).
4、1930s: NAD+ and FAD were found to be e- carriers between metabolites and the respiratory chain. 1930s: Role of ATP and general importance of phosphorylation in bioenergetics were realized.,1950s: Isolated mitochondria were found to effect the obligatory coupling of the phosphorylation of ADP and the
5、 e- transfer from NADH to O2. 1961, the chemiosmotic hypothesis was proposed for linking the e- transfer and ADP phosphorylation (based on the uncoupling phenomenon and the intactness requirement) 1960s, ATP synthase was identified from mitochondria.,概念：糖类、脂肪、蛋白质等有机物质在细胞中进行氧化分解生成CO2和H2O并释放出能量的过程称为生物
6、氧化（biological oxidation），其实质是需氧细胞在呼吸代谢过程中所进行的一系列氧化还原反应过程，所以又称为细胞氧化或细胞呼吸。,生物氧化,Concept of Biological Oxidation Oxidation of materials in the biological body Degradation of glucoses,fatty acids,proteins Release of energy Formation of CO2 and H2O Trap the energy released as ATP and Body heat,与非生物氧化相比:
7、相同点,生物氧化与非生物氧化的比较,化学本质相同，都是失电子反应，如脱氢、加氧、传出电子。失电子者为还原剂，是电子供体，得电子者为氧化剂，是电子受体。在生物体内，生物氧化有三种方式：加氧氧化，电子转移和脱氢氧化。 同种物质不论以何种方式氧化，所释放的能量相同。,Electron transfer via red-ox reactions generates biological energy,Oxidative reaction De-electron Dehydrate Add oxygen Reductive reaction Accept electron Add hydrate De-
8、oxygen,不同点： 生物氧化是酶促反应，反应条件（如温度、pH）温和；而体外燃烧则是剧烈的游离基反应，要求在高温、高压以及干燥的条件下进行。 生物氧化分阶段逐步缓慢地氧化，能量也逐步释放； 而体外燃烧能量是爆发式释放出来的。 生物氧化释放的能量有相当多的转换成ATP中活跃的化学能，用于各种生命活动；体外燃烧产生的能量则转换为光和热，散失在环境中。,CO2的生成,方式：生物氧化过程中生成的CO2并不是代谢物上的碳原子与吸入的氧直接化合的结果，而是有机酸脱羧作用生成的。糖、脂、蛋白质等有机物转变成含羧基的中间化合物，然后在酶催化下脱羧而生成CO2。 根据所脱羧基在有机酸分子中的位置，可将脱羧反
9、应分为脱羧和脱羧；又根据反应的同时是否伴有氧化反应，分为单纯脱羧和氧化脱羧。 类型：-脱羧和-脱羧（从脱羧的位置） 氧化脱羧和单纯脱羧 （脱羧方式）,Direct Decarboxylation,a,-,d,i,r,e,c,t,d,e,c,a,r,b,o,x,y,l,a,t,i,o,n,H,3,C,C,C,O,O,H,O,a,-,酮,酸,脱,羧,酶,M,g,2,+,T,P,P,H,3,C,C,O,H,+,C,O,2,Oxidative Decarboxylation,H2O的生成,代谢物在脱氢酶催化下脱下的氢由相应的氢载体（NAD+、NADP+、FAD、FMN等）所接受，再通过一系列递氢体或递
10、电子体传递给氧而生成H2O 。,12 O2,NAD+,电子传递链,H2O,2e,O=,2H+,脂肪,葡萄糖、其它单糖,三羧酸循环,电子传递（氧化）,蛋白质,脂肪酸、甘油,多糖,氨基酸,乙酰CoA,e-,磷酸化,+Pi,小分子化合物分解成共同的中间产物（如丙酮酸、乙酰CoA等）,共同中间产物进入三羧酸循环,氧化脱下的氢由电子传递链传递生成H2O，释放出大量能量，其中一部分通过磷酸化储存在ATP中。,大分子降解成基本结构单位,生物氧化的三个阶段,Biological oxidations are catalyzed by intracellular enzymes. The purpose of
11、oxidation is to obtain energy. Electron Transport: Electrons carried by reduced coenzymes (NADH or FADH2) are passed sequentially through a chain of proteins and coenzymes (so called electron transport chain)to O2 . Oxidative Phosphorylation: Coupling e- Transport (Oxidation) and ATP synthesis (Phos
12、phorylation) . It all happens in mitochondrion or at the inner mitochondrial membrane (eukaryotic cells),Impermeable to ions and most other compounds,In inner membrane knobs,the mitochondrion contained the enzymes responsible for electron transport and oxidative phosphorylation,Mitochondria,outer me
13、mbrane relatively permeable inner membrane permeable only to those things with specific transporters Impermeable to NADH and FADH2 Permeable to pyruvate Compartmentalization Krebs and -oxidation in matrix Glycolysis in cytosol,Most energy from Redox,electrons during metabolic reactions sent to NAD a
14、nd FAD Glycolysis In cytosol produces 2 NADH Pyruvate dehydrogenase reaction In mitochondrial matrix 2 NADH / glucose Krebs In mitochondrial matrix 6 NADH and 2 FADH2 / glucose,线粒体是生物氧化的发生场所,线粒体基质是呼吸底物氧化的场所，底物在这里氧化所产生的NADH和FADH2将质子和电子转移到内膜的载体上，经过一系列氢载体和电子载体的传递，最后传递给O2生成H2O。这种由载体组成的电子传递系统称电子传递链（eclct
15、ron transfer chain), 因为其功能和呼吸作用直接相关，亦称为呼吸链。 柠檬酸循环在线粒体基质中进行，电子传递和氧化磷酸化在线粒体内膜上进行。,电子传递链的概念,Electron Transport and Oxidative Phosphorylation,Electron transport and oxidative phosphorylation re-oxidize NADH and FADH2 and trap the energy released as ATP. In eukaryotes, electron transport and oxidative ph
16、osphorylation occur in the inner membrane of mitochondria whereas in prokaryotes the process occurs in the plasma membrane.,电子传递链的组成,呼吸电子传递链主要由蛋白质复合体组成，在线粒体内膜上有4种参与电子传递的蛋白质复合体，分别为 NADHQ还原酶（NADH-Q reductase） 琥珀酸Q还原酶（succinate-Q reductase） 细胞色素还原酶（cytochrome reductase） 细胞色素氧化酶（cytochrome oxidase）,洋地黄皂苷,Various prosthetic groups act as intermediate electron carriers in the respiratory chain,呼吸链的组成,1. 黄素蛋
