生物化学chap8TCAHMP.ppt

1、TCA, Tricarboxylic acid cycle Citric acid cycle,Definition,The cycle oxidizes pyruvate to CO2 and H2O , with the concomitant production of energy (ATP).,Location,The cycle occurs within the mitochondria（线粒体） of eukaryotes（真核生物） and cytosol（细胞质） of prokaryotes （原核生物）.,Section 1 The cycle process,Step

2、 1: pyruvate is converted to acetyl CoA by the enzyme pyruvate dehydrogenase,Pyruvate dehydrogenase is a complex of three enzymes; One NAD+ is reduced to NADH,Step 2: TCA The cycle carries out the oxidation of acetyl groups from acetyl CoA to CO2 with the production of four pairs of electrons, store

3、d initially in the reduced electron carriers NADH and FADH2.,TCA,草酰乙酸,柠檬酸,异柠檬酸,a-酮戊二酸,琥珀酸辅酶A,琥珀酸,延胡索酸,苹果酸,乙酰辅酶A,1.柠檬酸合成酶,2.顺乌头酸酶,3.异柠檬酸脱氢酶,4.a-酮戊二酸脱氢酶系,5.琥珀酸硫激酶,6.琥珀酸脱氢酶,7.延胡索酸水合酶,8.苹果酸脱氢酶,Step 3: Oxidation of NADH and FADH2,The NADH and FADH2 produced by the citric acid cycle are reoxidized and the

4、 energy released is used to synthesize ATP by oxidative phosphorylation.,Acetyl-CoA,2CO2,3NAD,3NADH+H,GDP,GTP,FAD,FADH2,Section 2 Energy yield,Each of the three NADH produced per turn of the cycle yields 3 ATPs and the single FADH2 yields 2 ATPs by oxidative phosphorylation. One GTP (or ATP) is synt

5、hesized directly during the conversion of succinyl CoA to succinate. Thus the oxidation of one acetyl CoA via TCA produces 12 ATP.,How many ATP molecules are generated with 1 molecule of pyruvate through TCA pathway?,How many ATP molecules are generated with 1 molecule of glucose through EMP-TCA pat

6、hway?( one glucose is oxidized to CO2 and H2O.),Oxidation of 2 pyr to 2 acetyl CoA: 2 NADH,Glycolysis: 2ATP, 2NADH,TCA: 6NADH, 2FADH2, 2GTP(ATP),Total: 103+22+4=38ATP,102.5+21.5+4=32ATP,EMP :8 Pyruvate to acetylCoA:6 TCA cycle:24,葡萄糖6O238ADP38Pi 6CO26H2O+38ATP,Physiological importance of EMP-TCA pat

7、hway,A common pathway for complete oxidation of carbohydrates into CO2 and H2O. Main source for energy supply To produce intermediates for biosynthetic pathways TCA is the common pathway for complete oxidative catabolism of macromolecules in organism (protein, nucleic acid and lipid),糖、脂、蛋白质等物质彻底氧化的

8、途径； 生成大量的ATP，是机体利用糖或其它物质氧化获得能量的最有效方式； 合成代谢提供原料; 糖、脂、蛋白质三大物质转化的枢纽.,Physiological importance of EMP-TCA,HMP,(Hexose monophosphate pathway) (pentose phosphate pathway, PPP),Introduction,Reducing power is available in a cell both as NADH and NADPH, but these have quite distinct roles.,The core set of re

9、actions of the pathway oxidize glucose 6-phosphate to ribose 5-phosphate and generate NADPH.,NADH is oxidized by the respiratory chain to generate ATP via oxidative phosphorylation. NADPH is used for biosynthetic reactions that require reducing power (such as synthesis of fatty acids and steroids),转

10、酮醇酶,转酮醇酶,转醛醇酶,Biochemical process ,6-phosphate glucose dehydrogenase,6-phosphate gluconic acid dehydrogenase,6(glucose-6-P)6O2 5(glucose-6-P)+6CO25H2O,62NADP,62NADPH+H,glucose,ATP,ADP,How many ATP molecules are generated with 1 molecule of pyruvate through TCA pathway?,Energy yield,35 ATP,Functions,

11、Another pathway for complete oxidation of carbohydrates; an assistant pathway of EMP (70% by EMP, 30% by HMP) To supply reducing power NADPH for biosynthetic reactions (lipid anabolism) Intermediates of HMP are used materials to synthesize compounds (such as ribose 5-phosphate)(An important pathway for pentose metabolism),gluconeogenesis (anabolism of glucose),Gluconeogenesis (糖的异生作用) the process for nonsugars (e