1、生物化学生物化学BIOCHEMISTRY Metabolism 新陈代谢新陈代谢Glycolysis 糖酵解糖酵解 the Universal Process In the cells cytoplasm胞浆where 6-carbon glucose is split into two 3-carbon pyruvate 丙酮酸盐molecules,and some ATP and NADH are produced.Nine reactions,each catalyzed by a specific enzyme,make up the process All organisms hav
2、e glycolysis occurring in their cytoplasmGraphic summary of the glycolysis process.烟酰胺腺嘌呤二核苷酸nicotinamide adenine dinucleotideAnaerobic Pathways 无氧途径无氧途径Anaerobic conditions:the absence of oxygen Pyruvic acid:routed into one of three pathways:lactic acid fermentation 乳酸发酵alcohol fermentation 酒精发酵cel
3、lular(anaerobic)respiration 细胞呼吸.Humans cannot ferment alcohol in their own bodies,we lack the genetic information to do so.These biochemical pathways,with their myriad reactions catalyzed by reaction-specific enzymes all under genetic control,are extremely complex.Alcohol FermentationFermentation:t
4、he formation of alcohol from sugar.Yeast,when under anaerobic conditions,convert glucose to pyruvic acid via the glycolysis pathways,then go one step farther,converting pyruvic acid into ethanol,a C-2 compound.Fermentation of ethanol.Image from Purves et al.Fermentation of lactate(lactic acid).Image
5、 from Purves et al.Aerobic Respiration 有氧呼吸有氧呼吸When oxygen is present(aerobic conditions),most organisms will undergo two more steps,Krebs Cycle,and Electron Transport,to produce their ATP.In eukaryotes 真核细胞,these processes occur in the mitochondria线粒体,while in prokaryotes原核细胞 they occur in the cyto
6、plasm.Overview of the cellular respiration processes.Image from Purves et alSummary of the Krebs(or citric acid)cycle.Image from Purves et al.Electron Transport Phosphorylation 电子传递磷酸化电子传递磷酸化Krebs cycle completely oxidized the carbons in the pyruvic acids,producing a small amount of ATP,and reducing
7、 NAD and FAD into higher energy forms.Electron Transport System(ETS):Its chemical is embedded in the membranes The higher energy forms are cashed in,producing ATP.Cytochromes are molecules that pass the hot potatoes(electrons)along the ETS chain.Energy released by the downhill passage of electrons i
8、s captured as ATP by ADP molecules oxidative phosphorylation.Figure 8.16 An electrogenic pumpOxidative PhosphorylationThe mechanism-chemiosmotic coupling,is the gradient of H+ions discovered across the inner mitochondrial membrane.Involves both chemical and transport processes.Drops in the potential
9、 energy of electrons moving down the ETS chain occur at three points.These points turn out to be where ADP+P are converted into ATP.Potential energy is captured by ADP and stored in the pyrophosphate bond.NADH enters the ETS chain at the beginning,yielding 3 ATP per NADH.FADH2 enters at Co-Q,produci
10、ng only 2 ATP per FADH2.Electron transport system.Images from Purves et al.Catabolism 分解代谢分解代谢and Anabolism合成代谢合成代谢 Anabolism:the total series of chemical reactions involved in synthesis of organic compounds.Autotrophs must be able to manufacture(synthesize)all the organic compounds they need.Hetero
11、trophs can obtain some of their compounds in their diet(along with their energy).For example humans can synthesize 12 of the 20 amino acids,we must obtain the other 8 in our diet.Catabolism:the series of chemical reactions that breakdown larger molecules.Energy is released this way,some of it can be utilized for anabolism.Products of catabolism can be reassembled by anabolic processes into new anabolic molecules.Catabolism and Anabolism
