Name: electron transport chain and atp production
Uploaded: 2025-08-01T06:51:24.000Z
Duration: 1 min 29 s
Channel: JoVE

A cadeia de transporte de elétrons consiste em quatro complexos proteicos associados à membrana na membrana mitocondrial interna dos eucariotos e na membrana plasmática dos procariotos. Esses complexos sofrem reações redox, transferindo elétrons através de transportadores como flavoproteínas FMN e FAD, proteínas ferro-enxofre, citocromos b, c1, c, a e a3 e quinonas como a coenzima Q, com potenciais redox variados. Flavoproteínas e quinonas transportam elétrons ao longo dos complexos de proteínas enquanto translocam prótons. As proteínas ferro-enxofre não possuem um grupo heme, enquanto os citocromos utilizam um grupo heme para o transporte de elétrons. A cadeia de transporte de elétrons começa com os elétrons se movendo de flavoproteínas para proteínas de ferro-enxofre e depois para quinonas. Os elétrons continuam através dos citocromos, atingindo o aceptor de elétrons terminal. A energia liberada durante a transferência de elétrons bombeia prótons através da membrana, gerando uma força motriz de prótons. Nas bactérias Gram-positivas, os prótons são bombeados para fora, enquanto nas bactérias Gram-negativas, eles se acumulam no espaço periplasmático antes da síntese de ATP.

componentes da cadeia transportadora de elétrons

Electron Transport Chain Components

A cadeia transportadora de el&#233;trons (CTE) &#233; uma via metab&#243;lica fundamental que facilita a convers&#227;o de energia em c&#233;lulas procari&#243;ticas e eucari&#243;ticas. Em organismos eucari&#243;ticos, a CTE compreende quatro complexos proteicos associados &#224; membrana mitocondrial interna. Em organismos procari&#243;ticos, a CTE na membrana plasm&#225;tica pode variar em sua composi&#231;&#227;o, apresentando menor n&#250;mero ou tipos distintos de complexos, dependendo do organismo e das condi&#231;&#245;es ambientais. Esses complexos transferem el&#233;trons de doadores de el&#233;trons, como NADH e FADH_2, para aceptores terminais de el&#233;trons, incluindo oxig&#234;nio na respira&#231;&#227;o aer&#243;bica e aceptores alternativos como nitrato na respira&#231;&#227;o anaer&#243;bica.
Carregadores de El&#233;trons e Rea&#231;&#245;es de Redox
A ETC &#233; composta por diversos carregadores de el&#233;trons essenciais, incluindo flavoprote&#237;nas, prote&#237;nas ferro-enxofre, citocromos e quinonas. As flavoprote&#237;nas, como o mononucleot&#237;deo de flavina (FMN) e o dinucleot&#237;deo de flavina e adenina (FAD), cont&#234;m grupos prost&#233;ticos derivados da riboflavina que facilitam a transfer&#234;ncia de el&#233;trons. As quinonas, como a coenzima Q (ubiquinona), s&#227;o pequenas mol&#233;culas lipossol&#250;veis que transportam el&#233;trons entre os complexos ao mesmo tempo que auxiliam na transloca&#231;&#227;o de pr&#243;tons. As prote&#237;nas ferro-enxofre n&#227;o possuem grupos heme e promovem a transfer&#234;ncia de el&#233;trons por meio de aglomerados ferro-enxofre redox-ativos. Em contraste, os citocromos cont&#234;m grupos prost&#233;ticos heme que passam por oxida&#231;&#227;o e redu&#231;&#227;o revers&#237;veis, permitindo a passagem sequencial de el&#233;trons pela cadeia.
Fluxo de El&#233;trons e For&#231;a Motriz de Pr&#243;tons
Em eucariotos, a transfer&#234;ncia de el&#233;trons inicia-se no Complexo I, onde o FMN recebe el&#233;trons do NADH e &#233; reduzida a FMNH_2. Esses el&#233;trons s&#227;o ent&#227;o transferidos para prote&#237;nas ferro-enxofre, que os direcionam para as quinonas, respons&#225;veis por transport&#225;-los at&#233; o Complexo III. O Complexo II tamb&#233;m participa do processo, fornecendo el&#233;trons derivados do FADH_2 diretamente &#224; ubiquinona. A partir desse ponto, as quinonas retransmitem os el&#233;trons ao citocromo c e, em seguida, ao Complexo IV, entregando-os, por fim, ao aceptor terminal de el&#233;trons.
A cadeia de transporte de el&#233;trons em procariontes apresenta grande varia&#231;&#227;o. Enquanto alguns utilizam complexos semelhantes aos dos eucariotos, outros recorrem a diferentes transportadores de el&#233;trons e aceptores terminais, de acordo com o ambiente e nutrientes dispon&#237;veis. Tanto em eucariotos quanto em procariontes, o fluxo de el&#233;trons est&#225; acoplado &#224; transloca&#231;&#227;o de pr&#243;tons atrav&#233;s da membrana, gerando a for&#231;a motriz de pr&#243;tons (FMP). A PMF estabelece um gradiente eletroqu&#237;mico que impulsiona a s&#237;ntese de ATP via a ATP sintase, em um processo conhecido como fosforila&#231;&#227;o oxidativa.
Transloca&#231;&#227;o de Pr&#243;tons em Bact&#233;rias
O mecanismo de transloca&#231;&#227;o de pr&#243;tons em c&#233;lulas procariontes varia de acordo com a estrutura do envelope celular. Em bact&#233;rias Gram-positivas, os pr&#243;tons s&#227;o bombeados diretamente para o exterior da membrana plasm&#225;tica, criando uma PMF que facilita a gera&#231;&#227;o de ATP. Em bact&#233;rias Gram-negativas, os pr&#243;tons se acumulam no espa&#231;o peripl&#225;smico, estabelecendo um gradiente semelhante necess&#225;rio para a s&#237;ntese de ATP. Esse processo &#233; essencial para a produ&#231;&#227;o de energia e apoia diversas atividades celulares, incluindo o transporte de nutrientes e a motilidade.

Componentes da Cadeia Transportadora de Elétrons

A cadeia transportadora de el&#233;trons (CTE) &#233; uma via metab&#243;lica fundamental que facilita a convers&#227;o de energia em c&#233;lulas ...

Education

JoVE Core

Microbiology

Microbiologia

Unit

Unidade

Microbial Metabolism

Metabolismo Microbiano

KEY TERMS AND CONCEPTS

TERMOS-CHAVE E CONCEITOS

electron transport chain and atp production

The electron transport chain helps cells make ATP by moving electrons through membrane protein complexes. In eukaryotic cells, it sits in the inner mitochondrial membrane. In prokaryotic cells, it is found in the plasma membrane and can differ in the number and type of complexes, depending on the organism and its environment.

The chain uses several electron carriers to pass electrons along in redox reactions, which are reactions that involve oxidation and reduction. These carriers include flavoproteins, iron-sulfur proteins, cytochromes, and quinones. Flavoproteins such as FMN and FAD contain riboflavin-based prosthetic groups. Quinones, such as coenzyme Q or ubiquinone, are lipid-soluble and shuttle electrons between complexes while helping with proton movement.

Iron-sulfur proteins do not contain heme groups. Instead, they use iron-sulfur clusters to move electrons from one carrier to the next. Cytochromes do contain heme prosthetic groups, and their heme iron can switch between oxidized and reduced states. This makes cytochromes useful for stepwise electron transfer through the chain.

In eukaryotes, electron flow begins in Complex I, where FMN accepts electrons from NADH and becomes FMNH2. The electrons then move to an iron-sulfur protein and then to quinones, which carry them to Complex III. Complex II also feeds electrons from FADH2 directly to ubiquinone. From there, the electrons move to cytochrome c and then to Complex IV, where they reach the terminal electron acceptor.

The terminal electron acceptor is oxygen in aerobic respiration. In some anaerobic respiration pathways, cells use alternative acceptors such as nitrate. In prokaryotes, the electron transport chain can vary widely, and some organisms use different electron carriers and acceptors based on available nutrients and conditions.

Electron flow is linked to proton translocation across the membrane. This creates a proton motive force, or PMF, which is an electrochemical gradient. The PMF powers ATP synthase and drives ATP production by oxidative phosphorylation.

Bacterial cells handle proton movement in different ways based on cell envelope structure. In Gram-positive bacteria, protons are pumped directly outside the plasma membrane. In Gram-negative bacteria, protons build up in the periplasmic space. In both cases, the gradient helps generate ATP and supports functions such as nutrient transport and motility.

Electron Transport Chain and ATP Production

electron-transport-chain-and-atp-production

microbial nutrition

Microbial Energy and Carbon Sources

Microbial energy and carbon sources determine how microorganisms live and grow. These metabolic strategies help microbes survive in many habitats and keep energy moving through ecosystems. They also support nutrient cycling in nature. Microbes are grouped by where they get energy, electrons, and carbon. Phototrophs use light, while chemotrophs use chemical compounds for energy. Lithotrophs take electrons from reduced inorganic substances, and organotrophs take them from organic compounds.

atp and energy production

How Cells Make and Use ATP

ATP is the main energy carrier in cells. It is made of adenosine, which includes adenine and ribose, plus three phosphate groups. The bonds between the phosphate groups hold a large amount of potential energy. When ATP is hydrolyzed, it becomes ADP or AMP and releases energy for cell work. Cells use that energy for many essential tasks. It supports macromolecule synthesis, intracellular transport, and mechanical movement. ATP also acts as an energy manager by linking catabolic and anabolic...

redox reactions

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introduction to metabolism

Metabolism: Energy Use and Biomolecule Synthesis

Metabolism is the set of chemical reactions that keep living cells working. It includes reactions that break down biomolecules and reactions that build them up. These two sides of metabolism work together to support energy balance and cell function. Catabolic pathways break large molecules into smaller parts. Carbohydrates, lipids, and proteins can be broken down into monosaccharides, fatty acids, and amino acids. These reactions release energy, and cells store much of that energy as ATP, or...

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glycolysis

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Glycolysis is a central pathway in glucose catabolism and a major way cells make energy. It is also called the Embden-Meyerhof pathway. This process takes place in the cytoplasm and can work with or without oxygen, which makes it useful in many organisms and conditions. Glycolysis has ten steps and turns one glucose molecule into two pyruvate molecules. It has two phases. In the preparatory phase, the cell uses two ATP to add phosphate groups to glucose and split it into two three-carbon...

other glycolytic pathways

Pentose Phosphate Pathway and Entner-Doudoroff

The pentose phosphate pathway works alongside glycolysis in cells that need both sugar breakdown and building blocks for growth. It handles pentoses, which are five-carbon sugars, and also uses glucose as a starting point. The pathway has two parts, an oxidative phase and a non-oxidative phase. It does not make ATP directly, but its products can feed back into glycolysis when the cell needs them. The oxidative phase mainly makes NADPH, a reduced electron carrier. In this phase,...

cellular respiration

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Cellular respiration is the process cells use to turn glucose into ATP, the main energy molecule in the cell. It depends on oxidation and the transfer of electrons to a separate electron acceptor. This sequence of reactions supports energy production in both aerobic and anaerobic settings. Glycolysis is the first step. It takes place in the cytoplasm of both prokaryotic and eukaryotic cells. One glucose molecule is broken into two pyruvate molecules, and the cell gains a net 2 ATP and 2 NADH.

electron transport chain components

The electron transport chain helps cells make ATP by moving electrons through membrane protein complexes. In eukaryotic cells, it sits in the inner mitochondrial membrane. In prokaryotic cells, it is found in the plasma membrane and can differ in the number and type of complexes, depending on the organism and its environment. The chain uses several electron carriers to pass electrons along in redox reactions, which are reactions that involve oxidation and reduction. These carriers include...

chemiosmosis and atp synthesis

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...

respiration pathways

TCA Cycle and Energy Pathways

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microbial fermentation

Fermentation Products in Microbes

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metabolism of chemolithotrophs

How Chemolithotrophs Make ATP

Chemolithotrophs make ATP by using inorganic chemicals as an energy source. They oxidize molecules such as hydrogen gas, ammonia, reduced sulfur compounds, and ferrous iron. Instead of relying on organic carbon like heterotrophs, they move electrons from these inorganic donors into the electron transport chain, or ETC. That electron flow builds a proton motive force, or PMF. The PMF drives ATP synthesis through oxidative phosphorylation. Because inorganic electron donors usually release less...

amino acid catabolism

Microbes Use Proteins for Energy

Microbes can use proteins as a carbon and energy source, especially when polysaccharides or lipids are scarce. But proteins are too large to pass through the plasma membrane on their own. To solve this, microbes secrete extracellular proteases and peptidases that break proteins into peptides. The peptides are then transported into the cell, where intracellular proteases cut them into free amino acids. Once amino acids are available, microbes break them down in two main ways: deamination and...

lipid catabolism

How Microbes Break Down Fats for Energy

Microbes break down triglycerides and fatty acids to make energy. Triglycerides are important long-term energy storage molecules in microorganisms. Lipases hydrolyze, or split with water, triglycerides into glycerol and free fatty acids. Each product then enters a different metabolic route that helps the cell make ATP, the main energy currency. Glycerol metabolism begins after glycerol is released from triglyceride hydrolysis. Glycerol kinase adds a phosphate group to form glycerol-3-phosphate.

oxygenic photosynthesis

How Plants Make Oxygen and ATP

Oxygenic photosynthesis is the process plants, algae, and cyanobacteria use to capture light energy and turn it into chemical energy. It uses water as the source of electrons and releases molecular oxygen, or O2. The process also produces ATP and NADPH, which cells need for later energy use and carbon fixation. The main reactions happen in the thylakoid membranes, where chlorophyll pigments absorb light. In cyanobacteria, these membranes come from folds in the plasma membrane. Two photosystems...

anoxygenic photosynthesis

Bacterial Light Capture Without Oxygen

Anoxygenic photosynthesis is a bacterial way to capture light energy without making oxygen. It supports carbon fixation, but it does not use water as the electron donor. Instead, these phototrophs use other electron donors such as hydrogen sulfide, elemental sulfur, thiosulfate, or organic compounds. This process is carried out by several groups of bacteria, including purple bacteria, green sulfur bacteria, heliobacteria, and other anoxygenic phototrophs. These organisms have evolved a...

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How Bacteria Build Key Macromolecules

Bacteria build essential macromolecules through tightly controlled biosynthetic pathways. These anabolic reactions make proteins, nucleic acids, lipids, and polysaccharides. The products support growth, cell division, and normal cell function. Bacterial biosynthesis starts with precursor metabolites from glycolysis, the pentose phosphate pathway, and the Krebs cycle. Important precursors include pyruvate, acetyl-CoA, and glucose-6-phosphate. Cells use these compounds to make the monomers that...

carbon-dioxide fixation

Microbial Carbon Fixation Pathways

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biosynthesis of polysaccharides

Activated Sugars for Polysaccharide Synthesis

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inorganic nitrogen assimilation

Nitrogen Uptake by Microbes

Nitrogen uptake by microbes is essential for making proteins, nucleic acids, and other cell parts. Many bacteria and archaea take in nitrogen as nitrate or ammonia. They then convert it into forms that can be built into biomolecules. When nitrate enters a cell, it goes through assimilatory nitrate reduction. This is a two-step process. First, nitrate reductase changes nitrate to nitrite using NADH or FAD as an electron donor, depending on environmental and cellular conditions. Then nitrite...

sulfur assimilation

Sulfur Uptake and Cysteine Synthesis

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amino acid biosynthetic pathways

Amino Acid Building from Cell Metabolites

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biosynthesis of nucleic acids

Nucleotide Building Blocks for DNA and RNA

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Lipopolysaccharides and Gram-Negative Defense

Lipopolysaccharides (LPS) are important parts of the outer membrane of Gram-negative bacteria. They help stabilize the membrane and help protect bacteria from host immune responses. LPS has three main parts: lipid A, a core oligosaccharide, and an O antigen. LPS biosynthesis and assembly depend on a coordinated set of enzymes and transport steps. The molecule is also known as an endotoxin. It can activate Toll-like receptor 4 (TLR4) in the host and trigger strong immune responses. In severe...

key terms and concepts

Explore how the electron transport chain moves electrons, builds a proton motive force, and helps cells make ATP in eukaryotes and prokaryotes.

Electron Transport Chain and ATP Production | 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 and ATP Production

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