Name: electron transport chain powers atp output
Uploaded: 2025-06-12T09:34:38.000Z
Duration: 1 min 22 s
Channel: JoVE

Durante a cadeia de transporte de elétrons, elétrons de alta energia de NADH e FADH₂ passam pelos complexos de proteínas que conduzem o bombeamento de prótons através da membrana. Os elétrons do NADH entram no Complexo I e se movem através dos complexos, bombeando aproximadamente dez prótons através dos complexos I, III e IV. Os elétrons do FADH₂ entram no Complexo II, que não bombeia prótons. Como resultado, o FADH2 contribui para bombear apenas seis prótons através da membrana. O movimento do próton cria um gradiente de concentração e um gradiente elétrico, gerando coletivamente a força motriz do próton. Os prótons fluem de volta através da membrana através da ATP sintase, um complexo enzimático ligado à membrana que usa a força motriz do próton para fosforilar o ADP em ATP - um processo chamado quimiosmose. A ATP sintase utiliza aproximadamente quatro prótons para sintetizar uma molécula de ATP. Como resultado, cerca de 2,5 moléculas de ATP são geradas por NADH e cerca de 1,5 moléculas de ATP são produzidas por FADH₂.

quimiosmose

Chemiosmosis and ATP Synthesis

A cadeia transportadora de el&#233;trons &#233; um componente cr&#237;tico da respira&#231;&#227;o celular, ocorrendo na membrana mitocondrial interna. Ela facilita a transfer&#234;ncia de el&#233;trons de alta energia a partir de cofatores reduzidos, como o NADH e o FADH_2, para o oxig&#234;nio molecular, o aceptor final de el&#233;trons. Essa transfer&#234;ncia de el&#233;trons atrav&#233;s de uma s&#233;rie de complexos proteicos est&#225; intimamente acoplada &#224; transloca&#231;&#227;o de pr&#243;tons atrav&#233;s da membrana, gerando um gradiente de pr&#243;tons essencial para a s&#237;ntese de ATP.
Fluxo de El&#233;trons e Bombeamento de Pr&#243;tons
Os el&#233;trons provenientes do NADH entram na cadeia transportadora de el&#233;trons no Complexo I (NADH: ubiquinona oxidoredutase). Em procariontes, &#224; medida que os el&#233;trons passam pelo Complexo I, impulsionam o bombeamento de pr&#243;tons do citoplasma para o espa&#231;o extracelular. Em seguida, os el&#233;trons s&#227;o transferidos para a ubiquinona (coenzima Q), que os transporta at&#233; o Complexo III (complexo citocromo bc1). O Complexo III facilita nova transfer&#234;ncia de el&#233;trons para o citocromo c, ao mesmo tempo em que bombeia pr&#243;tons adicionais. Por fim, os el&#233;trons chegam ao Complexo IV (citocromo c oxidase), onde reduzem o oxig&#234;nio molecular a &#225;gua. Esse complexo tamb&#233;m contribui para a transloca&#231;&#227;o de pr&#243;tons. Coletivamente, a passagem de el&#233;trons do NADH resulta no bombeamento de aproximadamente dez pr&#243;tons atrav&#233;s da membrana.
Em contraste, os el&#233;trons do FADH_2 entram na cadeia transportadora de el&#233;trons no Complexo II (succinato desidrogenase), contornando o Complexo I. O Complexo II n&#227;o possui capacidade de bombeamento de pr&#243;tons. Os el&#233;trons do FADH_2 s&#227;o transferidos para a ubiquinona e seguem caminho semelhante atrav&#233;s dos Complexos III e IV. O FADH_2 contribui para a transloca&#231;&#227;o de apenas seis pr&#243;tons atrav&#233;s da membrana.
For&#231;a Motriz de Pr&#243;tons e S&#237;ntese de ATP
O bombeamento diferencial de pr&#243;tons gera um gradiente tanto qu&#237;mico (de concentra&#231;&#227;o) quanto el&#233;trico (de voltagem) atrav&#233;s da membrana mitocondrial interna, coletivamente denominado for&#231;a motriz de pr&#243;tons. Esse gradiente eletroqu&#237;mico impulsiona os pr&#243;tons de volta para a matriz mitocondrial por meio da ATP sintase, um complexo enzim&#225;tico associado &#224; membrana. O processo de utiliza&#231;&#227;o da for&#231;a motriz de pr&#243;tons para fosforilar o ADP em ATP &#233; conhecido como quimiosmose.
A ATP sintase requer aproximadamente quatro pr&#243;tons para sintetizar uma mol&#233;cula de ATP. Devido &#224;s diferentes efici&#234;ncias de transloca&#231;&#227;o de pr&#243;tons, a oxida&#231;&#227;o de uma mol&#233;cula de NADH gera cerca de 2,5 mol&#233;culas de ATP, enquanto uma mol&#233;cula de FADH_2 produz aproximadamente 1,5 mol&#233;culas de ATP. Essa efici&#234;ncia destaca o papel fundamental da cadeia transportadora de el&#233;trons e da for&#231;a motriz de pr&#243;tons no metabolismo energ&#233;tico celular.

Quimiosmose

A cadeia transportadora de el&#233;trons &#233; um componente cr&#237;tico da respira&#231;&#227;o celular, ocorrendo na membrana mitocondrial interna. ...

Education

JoVE Core

Microbiology

Microbiologia

Unit

Unidade

Microbial Metabolism

Metabolismo Microbiano

KEY TERMS AND CONCEPTS

TERMOS-CHAVE E CONCEITOS

electron transport chain powers atp output

The electron transport chain powers ATP production during cellular respiration. It sits in the inner mitochondrial membrane and moves high-energy electrons from NADH and FADH2 to molecular oxygen, the final electron acceptor. As electrons move through the chain, protons are pushed across the membrane to build the gradient needed for ATP synthesis.

Electrons from NADH enter the chain at Complex I, also called NADH: ubiquinone oxidoreductase. In prokaryotes, this step helps pump protons from the cytoplasm into the extracellular space. The electrons then move to ubiquinone, or coenzyme Q, which carries them to Complex III, where more protons are pumped and electrons are passed to cytochrome c.

From Complex III, the electrons reach Complex IV, or cytochrome c oxidase. Here, molecular oxygen is reduced to water. Complex IV also helps move protons across the membrane. Overall, electrons that start with NADH lead to the pumping of about ten protons.

FADH2 follows a different route. Its electrons enter at Complex II, also called succinate dehydrogenase, which bypasses Complex I and does not pump protons. The electrons then move to ubiquinone and continue through Complex III and Complex IV. Because of this shorter path, FADH2 contributes only six protons to membrane transport.

The proton pumping creates a proton motive force. This force includes both a concentration gradient and a voltage gradient across the inner mitochondrial membrane. Protons flow back into the mitochondrial matrix through ATP synthase, a membrane enzyme that uses this energy to make ATP from ADP. This use of the proton motive force is called chemiosmosis.

ATP synthase needs about four protons to produce one ATP molecule. Because NADH and FADH2 move different numbers of protons, they yield different ATP amounts. One NADH molecule produces about 2.5 ATP, while one FADH2 molecule produces about 1.5 ATP. These values show how the electron transport chain links electron flow, proton movement, and cellular energy production.

Electron Transport Chain Powers ATP Output

electron-transport-chain-powers-atp-output

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chemiosmosis and atp synthesis

The electron transport chain powers ATP production during cellular respiration. It sits in the inner mitochondrial membrane and moves high-energy electrons from NADH and FADH2 to molecular oxygen, the final electron acceptor. As electrons move through the chain, protons are pushed across the membrane to build the gradient needed for ATP synthesis. Electrons from NADH enter the chain at Complex I, also called NADH: ubiquinone oxidoreductase. In prokaryotes, this step helps pump protons from the...

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key terms and concepts

Learn how the electron transport chain moves electrons, pumps protons, and drives ATP synthase to make ATP from NADH and FADH2 in cellular respiration.

Electron Transport Chain Powers ATP Output | JoVE K12

JoVE Core Microbiology provides an engaging introduction to the microbial world and its influence on health, industry, and the environment. This comprehensive collection covers key concepts such as microbial structure, metabolism, genetics, and ecology. It introduces essential laboratory techniques and microscopy methods through visually engaging animations. Corresponding scientist-in-action videos bridge classroom concepts with real-world research and applications.

microbiology

Electron Transport Chain Powers ATP Output

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