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微生物简单直接地将消化酶分泌到周围环境中<ref>{{cite journal | vauthors = Häse CC, Finkelstein RA | title = Bacterial extracellular zinc-containing metalloproteases | journal = Microbiological Reviews | volume = 57 | issue = 4 | pages = 823–37 | date = December 1993 | pmid = 8302217 | pmc = 372940 | doi = 10.1128/MMBR.57.4.823-837.1993 }}</ref><ref>{{cite journal | vauthors = Gupta R, Gupta N, Rathi P | title = Bacterial lipases: an overview of production, purification and biochemical properties | journal = Applied Microbiology and Biotechnology | volume = 64 | issue = 6 | pages = 763–81 | date = June 2004 | pmid = 14966663 | doi = 10.1007/s00253-004-1568-8  }}</ref>，而动物必须通过它们肠道(包括胃、胰腺和唾液腺)中的特定细胞分泌这些酶。<ref>{{cite journal | vauthors = Hoyle T | title = The digestive system: linking theory and practice | journal = British Journal of Nursing | volume = 6 | issue = 22 | pages = 1285–91 | year = 1997 | pmid = 9470654 | doi = 10.12968/bjon.1997.6.22.1285 }}</ref>这些细胞外酶释放的氨基酸或糖通过活性转运蛋白被泵入细胞内<ref>{{cite journal | vauthors = Souba WW, Pacitti AJ | title = How amino acids get into cells: mechanisms, models, menus, and mediators | journal = JPEN. Journal of Parenteral and Enteral Nutrition | volume = 16 | issue = 6 | pages = 569–78 | year = 1992 | pmid = 1494216 | doi = 10.1177/0148607192016006569 }}</ref><ref>{{cite journal | vauthors = Barrett MP, Walmsley AR, Gould GW | title = Structure and function of facilitative sugar transporters | journal = Current Opinion in Cell Biology | volume = 11 | issue = 4 | pages = 496–502 | date = August 1999 | pmid = 10449337 | doi = 10.1016/S0955-0674(99)80072-6 }}</ref>。

微生物简单直接地将消化酶分泌到周围环境中<ref>{{cite journal | vauthors = Häse CC, Finkelstein RA | title = Bacterial extracellular zinc-containing metalloproteases | journal = Microbiological Reviews | volume = 57 | issue = 4 | pages = 823–37 | date = December 1993 | pmid = 8302217 | pmc = 372940 | doi = 10.1128/MMBR.57.4.823-837.1993 }}</ref><ref>{{cite journal | vauthors = Gupta R, Gupta N, Rathi P | title = Bacterial lipases: an overview of production, purification and biochemical properties | journal = Applied Microbiology and Biotechnology | volume = 64 | issue = 6 | pages = 763–81 | date = June 2004 | pmid = 14966663 | doi = 10.1007/s00253-004-1568-8  }}</ref>，而动物必须通过它们肠道(包括胃、胰腺和唾液腺)中的特定细胞分泌这些酶。<ref>{{cite journal | vauthors = Hoyle T | title = The digestive system: linking theory and practice | journal = British Journal of Nursing | volume = 6 | issue = 22 | pages = 1285–91 | year = 1997 | pmid = 9470654 | doi = 10.12968/bjon.1997.6.22.1285 }}</ref>这些细胞外酶释放的氨基酸或糖通过活性转运蛋白被泵入细胞内<ref>{{cite journal | vauthors = Souba WW, Pacitti AJ | title = How amino acids get into cells: mechanisms, models, menus, and mediators | journal = JPEN. Journal of Parenteral and Enteral Nutrition | volume = 16 | issue = 6 | pages = 569–78 | year = 1992 | pmid = 1494216 | doi = 10.1177/0148607192016006569 }}</ref><ref>{{cite journal | vauthors = Barrett MP, Walmsley AR, Gould GW | title = Structure and function of facilitative sugar transporters | journal = Current Opinion in Cell Biology | volume = 11 | issue = 4 | pages = 496–502 | date = August 1999 | pmid = 10449337 | doi = 10.1016/S0955-0674(99)80072-6 }}</ref>。

[[File:Catabolism schematic.svg|thumb|left|upright=1.35|蛋白质，碳水化合物和脂肪分解代谢的简化概述 ]]

[[File:Catabolism schematic.svg|thumb|right|upright=1.35|蛋白质，碳水化合物和脂肪分解代谢的简化概述。 ]]

氧化磷酸化中，通过如柠檬酸循环等代谢途径，电子从被消化吸收的食物分子上转移到氧气上，并将产生的能量以ATP的方式储存起来。在真核生物中，这一过程是通过线粒体膜上的一系列膜蛋白来完成的，被称为电子传递链。而在原核生物中，这些蛋白质存在于细胞的内膜中。<ref>{{cite journal | vauthors = Hosler JP, Ferguson-Miller S, Mills DA | title = Energy transduction: proton transfer through the respiratory complexes | journal = Annual Review of Biochemistry | volume = 75 | issue =  | pages = 165–87 | year = 2006 | pmid = 16756489 | pmc = 2659341 | doi = 10.1146/annurev.biochem.75.062003.101730 }}</ref>这些蛋白质利用电子从还原性分子(如NADH)传递到氧气所释放的能量来泵送质子穿过细胞膜<ref>{{cite journal | vauthors = Schultz BE, Chan SI | title = Structures and proton-pumping strategies of mitochondrial respiratory enzymes | journal = Annual Review of Biophysics and Biomolecular Structure | volume = 30 | issue =  | pages = 23–65 | year = 2001 | pmid = 11340051 | doi = 10.1146/annurev.biophys.30.1.23 | url = https://authors.library.caltech.edu/1623/1/SCHarbbs01.pdf }}</ref>。

氧化磷酸化中，通过如柠檬酸循环等代谢途径，电子从被消化吸收的食物分子上转移到氧气上，并将产生的能量以ATP的方式储存起来。在真核生物中，这一过程是通过线粒体膜上的一系列膜蛋白来完成的，被称为电子传递链。而在原核生物中，这些蛋白质存在于细胞的内膜中。<ref>{{cite journal | vauthors = Hosler JP, Ferguson-Miller S, Mills DA | title = Energy transduction: proton transfer through the respiratory complexes | journal = Annual Review of Biochemistry | volume = 75 | issue =  | pages = 165–87 | year = 2006 | pmid = 16756489 | pmc = 2659341 | doi = 10.1146/annurev.biochem.75.062003.101730 }}</ref>这些蛋白质利用电子从还原性分子(如NADH)传递到氧气所释放的能量来泵送质子穿过细胞膜<ref>{{cite journal | vauthors = Schultz BE, Chan SI | title = Structures and proton-pumping strategies of mitochondrial respiratory enzymes | journal = Annual Review of Biophysics and Biomolecular Structure | volume = 30 | issue =  | pages = 23–65 | year = 2001 | pmid = 11340051 | doi = 10.1146/annurev.biophys.30.1.23 | url = https://authors.library.caltech.edu/1623/1/SCHarbbs01.pdf }}</ref>。

[[File:ATPsyn.gif|thumb|right|ATP合成酶的作用机制。ATP 显示为红色，ADP 和磷酸显示为粉红色，转柄亚基显示为黑色]]

[[File:ATPsyn.gif|thumb|right|ATP合成酶的作用机制。ATP 显示为红色，ADP 和磷酸显示为粉红色，转柄亚基显示为黑色。]]

将质子泵出线粒体，会在膜上形成质子浓度差，产生电化学梯度。<ref>{{cite journal | vauthors = Capaldi RA, Aggeler R | title = Mechanism of the F(1)F(0)-type ATP synthase, a biological rotary motor | journal = Trends in Biochemical Sciences | volume = 27 | issue = 3 | pages = 154–60 | date = March 2002 | pmid = 11893513 | doi = 10.1016/S0968-0004(01)02051-5 }}</ref>这种力量促使质子通过ATP合成酶的基座回到线粒体中。质子的流动使柄亚基旋转，从而改变合成酶域的活性位点的形状，使二磷酸腺苷磷酸化--变成ATP<ref name="Dimroth" />。

将质子泵出线粒体，会在膜上形成质子浓度差，产生电化学梯度。<ref>{{cite journal | vauthors = Capaldi RA, Aggeler R | title = Mechanism of the F(1)F(0)-type ATP synthase, a biological rotary motor | journal = Trends in Biochemical Sciences | volume = 27 | issue = 3 | pages = 154–60 | date = March 2002 | pmid = 11893513 | doi = 10.1016/S0968-0004(01)02051-5 }}</ref>这种力量促使质子通过ATP合成酶的基座回到线粒体中。质子的流动使柄亚基旋转，从而改变合成酶域的活性位点的形状，使二磷酸腺苷磷酸化--变成ATP<ref name="Dimroth" />。

更多信息：光合作用，碳固定和化学合成

更多信息：光合作用，碳固定和化学合成

[[File:Plagiomnium affine laminazellen.jpeg|thumb|含叶绿体（绿色）的植物细胞（以紫色壁为边界），叶绿体是光合作用的部位]]

[[File:Plagiomnium affine laminazellen.jpeg|thumb|含叶绿体（绿色）的植物细胞（以紫色壁为边界），叶绿体是光合作用的部位。]]

光合作用就是依靠阳光和二氧化碳(CO₂)合成碳水化合物。在植物中，蓝细菌和藻类的含氧光合作用使水分解，排出氧气。如前所述，这一过程利用光合反应中心产生的ATP和NADPH将CO₂转化为三磷酸甘油酯，然后再转化为葡萄糖。这个固碳反应作为卡尔文-本森Calvin – Benson 循环的一部分是在RuBisCO酶的催化下进行的<ref>{{cite journal | vauthors = Miziorko HM, Lorimer GH | title = Ribulose-1,5-bisphosphate carboxylase-oxygenase | journal = Annual Review of Biochemistry | volume = 52 | issue =  | pages = 507–35 | year = 1983 | pmid = 6351728 | doi = 10.1146/annurev.bi.52.070183.002451 }}</ref>。植物有三种类型的光合作用:C3固碳、C4固碳和CAM光合作用。它们的不同之处在于二氧化碳进入卡尔文循环的路径不同，C3植物直接固定二氧化碳，而C4和CAM植物首先将二氧化碳吸收到其他化合物中，以适应强烈的阳光和干燥的环境<ref>{{cite journal | vauthors = Dodd AN, Borland AM, Haslam RP, Griffiths H, Maxwell K | title = Crassulacean acid metabolism: plastic, fantastic | journal = Journal of Experimental Botany | volume = 53 | issue = 369 | pages = 569–80 | date = April 2002 | pmid = 11886877 | doi = 10.1093/jexbot/53.369.569 | doi-access = free }}</ref>。

光合作用就是依靠阳光和二氧化碳(CO₂)合成碳水化合物。在植物中，蓝细菌和藻类的含氧光合作用使水分解，排出氧气。如前所述，这一过程利用光合反应中心产生的ATP和NADPH将CO₂转化为三磷酸甘油酯，然后再转化为葡萄糖。这个固碳反应作为卡尔文-本森Calvin – Benson 循环的一部分是在RuBisCO酶的催化下进行的<ref>{{cite journal | vauthors = Miziorko HM, Lorimer GH | title = Ribulose-1,5-bisphosphate carboxylase-oxygenase | journal = Annual Review of Biochemistry | volume = 52 | issue =  | pages = 507–35 | year = 1983 | pmid = 6351728 | doi = 10.1146/annurev.bi.52.070183.002451 }}</ref>。植物有三种类型的光合作用:C3固碳、C4固碳和CAM光合作用。它们的不同之处在于二氧化碳进入卡尔文循环的路径不同，C3植物直接固定二氧化碳，而C4和CAM植物首先将二氧化碳吸收到其他化合物中，以适应强烈的阳光和干燥的环境<ref>{{cite journal | vauthors = Dodd AN, Borland AM, Haslam RP, Griffiths H, Maxwell K | title = Crassulacean acid metabolism: plastic, fantastic | journal = Journal of Experimental Botany | volume = 53 | issue = 369 | pages = 569–80 | date = April 2002 | pmid = 11886877 | doi = 10.1093/jexbot/53.369.569 | doi-access = free }}</ref>。

新陈代谢的科学研究历史跨越了几个世纪，从早期研究中对动物整体的研究，到现代生物化学中对单个代谢反应的研究。 人类新陈代谢的第一个对照实验是由圣托里奥·桑托里奥 Santorio Santorio于1614年在他的著作《静态医学》中发表的<ref>{{cite journal | vauthors = Eknoyan G | title = Santorio Sanctorius (1561-1636) - founding father of metabolic balance studies | journal = American Journal of Nephrology | volume = 19 | issue = 2 | pages = 226–33 | year = 1999 | pmid = 10213823 | doi = 10.1159/000013455 }}</ref>。他描述了自己在进食、睡觉、工作、性交、禁食、饮水和排泄前后的体重。他发现他摄入的大部分食物都是通过他所谓的“无知觉的汗液”流失的。

新陈代谢的科学研究历史跨越了几个世纪，从早期研究中对动物整体的研究，到现代生物化学中对单个代谢反应的研究。 人类新陈代谢的第一个对照实验是由圣托里奥·桑托里奥 Santorio Santorio于1614年在他的著作《静态医学》中发表的<ref>{{cite journal | vauthors = Eknoyan G | title = Santorio Sanctorius (1561-1636) - founding father of metabolic balance studies | journal = American Journal of Nephrology | volume = 19 | issue = 2 | pages = 226–33 | year = 1999 | pmid = 10213823 | doi = 10.1159/000013455 }}</ref>。他描述了自己在进食、睡觉、工作、性交、禁食、饮水和排泄前后的体重。他发现他摄入的大部分食物都是通过他所谓的“无知觉的汗液”流失的。

[[File:SantoriosMeal.jpg|thumb|right|upright=0.7|Santorio Santorio 在他的杆秤上，来自静态医学，1614年首次发表]]

[[File:SantoriosMeal.jpg|thumb|right|upright=0.7|Santorio Santorio 在他的杆秤上，来自静态医学，1614年首次发表。]]

在早期的研究中，这些新陈代谢过程的机制还没有确定，人们认为一种生命力量是生命组织的活力<ref>{{cite book|url=https://archive.org/details/historyofscience04willuoft/page/n7/mode/2up|title=Modern Development of the Chemical and Biological Sciences|vauthors=Williams HA|date=1904|publisher=Harper and Brothers|isbn=|series=A History of Science: in Five Volumes|volume=IV|location=New York|pages=184–185|access-date=26 March 2007}}</ref>。19世纪，路易-巴斯德Louis Pasteur 在研究酵母菌将糖发酵成酒精时，得出结论：发酵是由酵母细胞内的物质催化的，他称之为 "发酵物"。他写道："酒精发酵是与酵母细胞的生命和组织有关的行为，而与细胞的死亡或腐烂无关"。这一发现<ref>{{cite journal | vauthors = Manchester KL | title = Louis Pasteur (1822-1895)--chance and the prepared mind | journal = Trends in Biotechnology | volume = 13 | issue = 12 | pages = 511–5 | date = December 1995 | pmid = 8595136 | doi = 10.1016/S0167-7799(00)89014-9 }}</ref>连同1828年弗里德里希-沃勒Friedrich Wöhler 发表的一篇关于尿素化学合成的论文<ref>{{cite journal | vauthors = Kinne-Saffran E, Kinne RK | title = Vitalism and synthesis of urea. From Friedrich Wöhler to Hans A. Krebs | journal = American Journal of Nephrology | volume = 19 | issue = 2 | pages = 290–4 | year = 1999 | pmid = 10213830 | doi = 10.1159/000013463  }}</ref>，因为是第一个完全由无机前体制备的有机化合物而引人注目。这证明了在细胞中发现的有机化合物和化学反应与化学的任何其他部分在原理上没有什么不同。

在早期的研究中，这些新陈代谢过程的机制还没有确定，人们认为一种生命力量是生命组织的活力<ref>{{cite book|url=https://archive.org/details/historyofscience04willuoft/page/n7/mode/2up|title=Modern Development of the Chemical and Biological Sciences|vauthors=Williams HA|date=1904|publisher=Harper and Brothers|isbn=|series=A History of Science: in Five Volumes|volume=IV|location=New York|pages=184–185|access-date=26 March 2007}}</ref>。19世纪，路易-巴斯德Louis Pasteur 在研究酵母菌将糖发酵成酒精时，得出结论：发酵是由酵母细胞内的物质催化的，他称之为 "发酵物"。他写道："酒精发酵是与酵母细胞的生命和组织有关的行为，而与细胞的死亡或腐烂无关"。这一发现<ref>{{cite journal | vauthors = Manchester KL | title = Louis Pasteur (1822-1895)--chance and the prepared mind | journal = Trends in Biotechnology | volume = 13 | issue = 12 | pages = 511–5 | date = December 1995 | pmid = 8595136 | doi = 10.1016/S0167-7799(00)89014-9 }}</ref>连同1828年弗里德里希-沃勒Friedrich Wöhler 发表的一篇关于尿素化学合成的论文<ref>{{cite journal | vauthors = Kinne-Saffran E, Kinne RK | title = Vitalism and synthesis of urea. From Friedrich Wöhler to Hans A. Krebs | journal = American Journal of Nephrology | volume = 19 | issue = 2 | pages = 290–4 | year = 1999 | pmid = 10213830 | doi = 10.1159/000013463  }}</ref>，因为是第一个完全由无机前体制备的有机化合物而引人注目。这证明了在细胞中发现的有机化合物和化学反应与化学的任何其他部分在原理上没有什么不同。