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

La respiration cellulaire est un processus biochimique qui génère de l’ATP par oxydation de molécules, à l’aide d’un accepteur d’électrons externe. Il commence par la glycolyse, convertissant le glucose en pyruvate tout en produisant de l’ATP et du NADH. Le pyruvate entre dans le cycle de Krebs, se produisant dans le cytoplasme des procaryotes ou la matrice mitochondriale des eucaryotes, générant du NADH et du FADH2. Les électrons de ces porteurs passent à travers la chaîne de transport d’électrons, située dans la membrane plasmique des procaryotes et la membrane mitochondriale interne des eucaryotes, produisant de l’ATP par phosphorylation oxydative. La respiration aérobie utilise l’oxygène comme accepteur d’électrons et peut produire jusqu’à 38 ATP par molécule de glucose chez les procaryotes. Chez les eucaryotes, le rendement net est d’environ 30 à 32 ATP, car une partie de l’énergie est consommée lors de la navette NADH. Certains procaryotes et eucaryotes subissent une respiration anaérobie qui utilise d’autres accepteurs d’électrons tels que le nitrate ou le sulfate comme accepteur d’électrons avec moins de rendements en ATP.

respiration

Cellular Respiration

La respiration cellulaire est un processus m&#233;tabolique fondamental par lequel les cellules obtiennent de l'&#233;nergie &#224; partir de substances organiques, principalement le glucose, afin de produire de l'ad&#233;nosine triphosphate (ATP). Ce processus comprend l'oxydation des substrats et le transfert d'&#233;lectrons vers un accepteur d'&#233;lectrons distinct, facilitant ainsi la synth&#232;se d'ATP au travers d'une s&#233;quence de r&#233;actions biochimiques.
Glycolyse : l'&#233;tape initiale
La glycolyse constitue la premi&#232;re &#233;tape de la respiration cellulaire, se d&#233;roulant dans le cytoplasme des cellules procaryotes et eucaryotes. Elle implique la d&#233;gradation d'une mol&#233;cule de glucose (C_6 H_12 O_6) en deux mol&#233;cules de pyruvate (C_3 H_4 O_3), avec un gain net de 2 ATP et 2 NADH. Ce processus ne requiert pas d'oxyg&#232;ne et sert d'&#233;tape pr&#233;paratoire &#224; la respiration a&#233;robie comme ana&#233;robie.
Le cycle de Krebs : production de transporteurs d'&#233;lectrons
Le pyruvate subit un processus crucial appel&#233; d&#233;carboxylation, au cours duquel il est converti en ac&#233;tyl-CoA. Cet ac&#233;tyl-CoA nouvellement form&#233; entre alors dans le cycle de Krebs, &#233;galement appel&#233; cycle de l'acide citrique ou cycle des acides tricarboxyliques. Cette s&#233;rie complexe de r&#233;actions biochimiques se produit dans le cytoplasme des procaryotes et dans la matrice mitochondriale des eucaryotes.
Au fur et &#224; mesure de sa progression dans le cycle de Krebs, l&#8217;ac&#233;tyl-CoA joue un r&#244;le essentiel dans la production d&#8217;&#233;nergie. Pour chaque mol&#233;cule d&#8217;ac&#233;tyl-CoA trait&#233;e, le cycle g&#233;n&#232;re trois mol&#233;cules de NADH, une mol&#233;cule de FADH_2 et une mol&#233;cule de GTP. Ces transporteurs d&#8217;&#233;lectrons, NADH et FADH_2, sont indispensables pour alimenter la synth&#232;se d&#8217;ATP lors des r&#233;actions suivantes. De plus, du dioxyde de carbone (CO_2) est lib&#233;r&#233; en tant que sous-produit durant ce processus, contribuant aux activit&#233;s m&#233;taboliques globales de la cellule.
Cha&#238;ne de transport d&#8217;&#233;lectrons et phosphorylation oxydative
La cha&#238;ne de transport d&#8217;&#233;lectrons (ETC en anglais) se situe dans la membrane plasmique des procaryotes, tandis que chez les eucaryotes, elle se trouve dans la membrane mitochondriale interne. Les &#233;lectrons provenant du NADH et du FADH_2 sont transf&#233;r&#233;s &#224; travers une s&#233;rie de complexes prot&#233;iques, cr&#233;ant un gradient de protons de part et d'autre de la membrane. Le retour des protons via l&#8217;ATP synthase entra&#238;ne la phosphorylation de l&#8217;ADP en ATP. Lors de la respiration a&#233;robie, l&#8217;oxyg&#232;ne agit comme accepteur final d&#8217;&#233;lectrons, formant de l&#8217;eau (H_2O).
Rendement en ATP et accepteurs d&#8217;&#233;lectrons alternatifs
La respiration a&#233;robie peut produire jusqu&#8217;&#224; 38 mol&#233;cules d&#8217;ATP par glucose chez les procaryotes, tandis que chez les eucaryotes, la production nette est d&#8217;environ 30 &#224; 32 ATP, en raison des co&#251;ts &#233;nerg&#233;tiques associ&#233;s au transport du NADH dans les mitochondries. Dans la respiration ana&#233;robie, les procaryotes et certains eucaryotes utilisent des accepteurs d&#8217;&#233;lectrons alternatifs comme le nitrate (NO_3^-), le sulfate (SO_4^2-) ou le dioxyde de carbone (CO_2), g&#233;n&#233;rant beaucoup moins d&#8217;ATP&#8212;g&#233;n&#233;ralement environ 2 ATP par glucose&#8212;en raison de la moindre efficacit&#233; de ces accepteurs dans la cr&#233;ation d&#8217;un gradient de protons.
La respiration cellulaire est essentielle au m&#233;tabolisme &#233;nerg&#233;tique, permettant aux organismes de maintenir leurs fonctions cellulaires gr&#226;ce &#224; la production d&#8217;ATP. L&#8217;efficacit&#233; et le choix de l&#8217;accepteur d&#8217;&#233;lectrons d&#233;terminent le rendement &#233;nerg&#233;tique et les adaptations m&#233;taboliques des diff&#233;rents organismes selon leur environnement.

Respiration

La respiration cellulaire est un processus m&#233;tabolique fondamental par lequel les cellules obtiennent de l'&#233;nergie &#224; partir de substances ...

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Microbial Metabolism

Métabolisme microbien

KEY TERMS AND CONCEPTS

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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

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...

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Metabolism: Energy Use and Biomolecule Synthesis

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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

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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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...

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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

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

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How Bacteria Build Key Macromolecules

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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

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sulfur assimilation

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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