Name: cellular respiration: atp production pathways
Uploaded: 2025-06-12T09:34:08.000Z
Duration: 1 min 18 s
Channel: JoVE

A respiração celular é um processo bioquímico que gera ATP através da oxidação de moléculas, usando um aceptor de elétrons externo. Começa com a glicólise, convertendo glicose em piruvato enquanto produz ATP e NADH. O piruvato entra no ciclo de Krebs, ocorrendo no citoplasma dos procariontes ou na matriz mitocondrial dos eucariotos, gerando NADH e FADH2. Os elétrons desses portadores passam pela cadeia de transporte de elétrons, localizada na membrana plasmática dos procariontes e na membrana mitocondrial interna dos eucariotos, produzindo ATP via fosforilação oxidativa. A respiração aeróbica usa oxigênio como aceptor de elétrons e pode produzir até 38 ATP por molécula de glicose em procariotos. Em eucariotos, o rendimento líquido é de cerca de 30 a 32 ATP, pois alguma energia é consumida durante o transporte de NADH. Alguns procariontes e eucariotos sofrem respiração anaeróbica que utiliza aceptores de elétrons alternativos, como nitrato ou sulfato, como aceptor de elétrons com menos rendimentos de ATP.

respiração

Cellular Respiration

A respira&#231;&#227;o celular &#233; um processo metab&#243;lico crucial por meio do qual as c&#233;lulas obt&#234;m energia a partir de subst&#226;ncias org&#226;nicas, principalmente a glicose, para produzir trifosfato de adenosina (ATP). Esse processo inclui a oxida&#231;&#227;o de substratos e a transfer&#234;ncia de el&#233;trons para um aceptor eletr&#244;nico distinto, facilitando a s&#237;ntese de ATP por meio de uma sequ&#234;ncia de rea&#231;&#245;es bioqu&#237;micas.
Glic&#243;lise: A Etapa Inicial
A glic&#243;lise &#233; a primeira etapa da respira&#231;&#227;o celular, ocorrendo no citoplasma de c&#233;lulas procari&#243;ticas e eucari&#243;ticas. Envolve a quebra de uma mol&#233;cula de glicose (C_6H_12O_6) em duas mol&#233;culas de piruvato (C_3H_4O_3), com um ganho l&#237;quido de 2 ATP e 2 NADH. Esse processo n&#227;o requer oxig&#234;nio e serve como etapa preparat&#243;ria para a respira&#231;&#227;o aer&#243;bica e anaer&#243;bica.
Ciclo de Krebs: Gera&#231;&#227;o de Carreadores de El&#233;trons
O piruvato passa por um processo crucial denominado descarboxila&#231;&#227;o, durante o qual &#233; convertido em acetil-CoA. Esse acetil-CoA rec&#233;m-formado entra ent&#227;o no ciclo de Krebs, tamb&#233;m conhecido como ciclo do &#225;cido c&#237;trico ou ciclo dos &#225;cidos tricarbox&#237;licos. Essa s&#233;rie intrincada de rea&#231;&#245;es bioqu&#237;micas ocorre no citoplasma dos procariontes e na matriz mitocondrial dos eucariontes.
&#192; medida que o acetil-CoA progride pelo ciclo de Krebs, desempenha um papel vital na produ&#231;&#227;o de energia. Para cada mol&#233;cula de acetil-CoA processada, o ciclo gera tr&#234;s mol&#233;culas de NADH, uma mol&#233;cula de FADH_2 e uma de GTP. Esses carreadores de el&#233;trons, NADH e FADH_2, s&#227;o essenciais para impulsionar a s&#237;ntese de ATP nas rea&#231;&#245;es subsequentes. Al&#233;m disso, o di&#243;xido de carbono (CO_2) &#233; liberado como subproduto durante esse processo, contribuindo para as atividades metab&#243;licas da c&#233;lula.
Cadeia de Transporte de El&#233;trons e Fosforila&#231;&#227;o Oxidativa
A cadeia transportadora de el&#233;trons (ETC) est&#225; localizada na membrana plasm&#225;tica dos procariontes, enquanto nos eucariontes encontra-se na membrana mitocondrial interna. El&#233;trons provenientes do NADH e FADH_2 s&#227;o transferidos atrav&#233;s de uma s&#233;rie de complexos proteicos, criando um gradiente de pr&#243;tons atrav&#233;s da membrana. O retorno dos pr&#243;tons por meio da ATP sintase impulsiona a fosforila&#231;&#227;o do ADP em ATP. Na respira&#231;&#227;o aer&#243;bica, o oxig&#234;nio atua como aceptor final de el&#233;trons, formando &#225;gua (H_2O).
Rendimento de ATP e Aceptores Alternativos de El&#233;trons
A respira&#231;&#227;o aer&#243;bica pode gerar at&#233; 38 mol&#233;culas de ATP por mol&#233;cula de glicose em procariontes, enquanto em eucariontes a produ&#231;&#227;o l&#237;quida de ATP &#233; de aproximadamente 30 a 32, devido aos custos energ&#233;ticos associados ao transporte de NADH para dentro das mitoc&#244;ndrias. Na respira&#231;&#227;o anaer&#243;bica, procariontes e alguns eucariontes utilizam aceptores alternativos de el&#233;trons, como nitrato (NO_3^-), sulfato (SO_4^2-) ou di&#243;xido de carbono (CO_2), resultando em um rendimento significativamente menor de ATP&#8212;tipicamente cerca de 2 ATP por glicose&#8212;devido &#224; menor efici&#234;ncia desses aceptores na gera&#231;&#227;o do gradiente de pr&#243;tons.
A respira&#231;&#227;o celular &#233; essencial para o metabolismo energ&#233;tico, permitindo que os organismos sustentem fun&#231;&#245;es celulares por meio da produ&#231;&#227;o de ATP. A efici&#234;ncia e a escolha do aceptor de el&#233;trons determinam o rendimento energ&#233;tico e as adapta&#231;&#245;es metab&#243;licas de diferentes organismos em variados ambientes.

Respiração

A respira&#231;&#227;o celular &#233; um processo metab&#243;lico crucial por meio do qual as c&#233;lulas obt&#234;m energia a partir de subst&#226;ncias ...

Education

JoVE Core

Microbiology

Microbiologia

Unit

Unidade

Microbial Metabolism

Metabolismo Microbiano

KEY TERMS AND CONCEPTS

TERMOS-CHAVE E CONCEITOS

cellular respiration: atp production pathways

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. Glycolysis does not require oxygen, so it can support both aerobic and anaerobic respiration.

Pyruvate then undergoes decarboxylation and becomes acetyl-CoA. Acetyl-CoA enters the Krebs cycle, also called the citric acid cycle or tricarboxylic acid cycle. In prokaryotes, this cycle occurs in the cytoplasm. In eukaryotes, it occurs in the mitochondrial matrix. Each acetyl-CoA produces 3 NADH, 1 FADH2, and 1 GTP. The cycle also releases carbon dioxide as a byproduct.

The electron transport chain, or ETC, uses the NADH and FADH2 made earlier. In prokaryotes, the ETC is in the plasma membrane. In eukaryotes, it is in the inner mitochondrial membrane. Electrons move through protein complexes and create a proton gradient across the membrane. ATP synthase uses the return flow of protons to convert ADP into ATP. In aerobic respiration, oxygen is the final electron acceptor, and water forms.

Aerobic respiration can yield up to 38 ATP per glucose in prokaryotes. In eukaryotes, the net yield is about 30 to 32 ATP because energy is used to move NADH into mitochondria. Some organisms also use anaerobic respiration. In that pathway, alternative electron acceptors such as nitrate, sulfate, or carbon dioxide are used. This form makes much less ATP, usually around 2 ATP per glucose, because these acceptors build a weaker proton gradient. Cellular respiration is therefore essential for ATP production and for the energy metabolism that keeps cells functioning.

Cellular Respiration: ATP Production Pathways

cellular-respiration-atp-production-pathways

microbial nutrition

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atp and energy production

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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...

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Glucose breakdown is a key part of cell metabolism that lets cells make ATP, the usable form of energy. The process follows two main paths: cellular respiration and fermentation. Both start with glycolysis, which does not require oxygen. Glycolysis splits one glucose molecule into two molecules of pyruvic acid. It also produces a net gain of two ATP molecules and two NADH molecules. This step sets up the cell to continue with respiration or switch to fermentation, depending on whether oxygen...

glycolysis

Glycolysis and Pyruvate Fate

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

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

Electron Transport Chain and ATP Production

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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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Fermentation Products in Microbes

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How Chemolithotrophs Make ATP

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Microbes Use Proteins for Energy

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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

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Bacterial Light Capture Without Oxygen

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How Bacteria Build Key Macromolecules

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biosynthesis of polysaccharides

Activated Sugars for Polysaccharide Synthesis

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inorganic nitrogen assimilation

Nitrogen Uptake by Microbes

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Sulfur Uptake and Cysteine Synthesis

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Amino Acid Building from Cell Metabolites

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Nucleotide Building Blocks for DNA and RNA

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key terms and concepts

Learn how cells make ATP through glycolysis, the Krebs cycle, and the electron transport chain, plus how aerobic and anaerobic respiration differ.

Cellular Respiration: ATP Production Pathways | 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

Cellular Respiration: ATP Production Pathways

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