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Related Concept Videos

Oxidation of Phenols to Quinones01:17

Oxidation of Phenols to Quinones

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In the presence of oxidizing agents, phenols are oxidized to quinones. Quinones can be easily reduced back to phenols using mild reducing agents. The electron-donating hydroxyl group enhances the reactivity of the aromatic ring, enabling oxidation of the ring even in the absence of an α hydrogen.
o-hydroxy phenols are oxidized to o-quinones and p-hydroxy phenols to p-quinones. Such redox reactions involve the transfer of two electrons and two protons. The reversible redox...
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The mitochondrial electron transport chain (ETC) is the main energy generation system in the eukaryotic cells. However, mitochondria also produce cytotoxic reactive oxygen species (ROS) due to the large electron flow during oxidative phosphorylation. While Complex I is one of the primary sources of superoxide radicals, ROS production by Complex II is uncommon and may only be observed in cancer cells with mutated complexes.
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Electron Transport Chain: Complex III and IV01:43

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During the electron transport chain, electrons from NADH and FADH2 are first transferred to complexes I and II, respectively. These two complexes then transfer the electrons to ubiquinol, which carries them further to complex III. Complex III passes the electrons across the intermembrane space to Cyt c, which carries them further to complex IV. Complex IV donates electrons to oxygen and reduces it to water. As electrons pass through complexes I, III, and IV, the energy released aids the pumping...
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The electron transport chain or oxidative phosphorylation is an exothermic process in which free energy released during electron transfer reactions is coupled to ATP synthesis. This process is a significant source of energy in aerobic cells, and therefore inhibitors of the electron transport chain can be detrimental to the cell's metabolic processes.
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The Photochemical Reaction Center01:29

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Reaction centers are pigment-protein complexes that initiate energy conversion from photons to chemical entities. Therefore, photochemical reaction center is a more appropriate term that describes these complexes. The Nobel laureates Robert Emerson and William Arnold provided the first experimental evidence of photochemical reaction centers by demonstrating the participation of nearly 2,500 chlorophyll molecules for the release of just one molecule of oxygen. Despite thousands of photosynthetic...
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Phase I biotransformation reductive reactions are chemical processes that modify drugs by introducing or revealing polar functional groups via reduction. Enzymes called reductases catalyze these reactions, playing a pivotal role in drug metabolism by transforming lipophilic drugs into more polar, water-soluble metabolites for easy excretion. An essential type of reductive reaction is the carbonyl group reduction, where aldehydes and ketones are reduced to alcohols. An example is the...
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Related Experiment Video

Updated: Jun 22, 2025

Monitoring the Reductive and Oxidative Half-Reactions of a Flavin-Dependent Monooxygenase using Stopped-Flow Spectrophotometry
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The monotopic quinone reductases from Staphylococcus aureus.

Patrícia M Pires1, David Santos1, Filipa Calisto1

  • 1University of Lisbon, Faculty of Sciences, Department of Chemistry and Biochemistry and BioISI - Biosystems & Integrative Sciences Institute, Campo Grande, C8, 1749-016 Lisboa, Portugal.

Biochimica Et Biophysica Acta. Bioenergetics
|July 1, 2024
PubMed
Summary

This study investigates the under-explored energetic metabolism of Staphylococcus aureus, focusing on its respiratory enzymes. We identified and described key monotopic quinone reductases, crucial for the bacterium's adaptability and survival in diverse oxygen environments.

Keywords:
DihydroorotateGlycerol-3-phosphateLactateMalateNADHSuccinate

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Last Updated: Jun 22, 2025

Monitoring the Reductive and Oxidative Half-Reactions of a Flavin-Dependent Monooxygenase using Stopped-Flow Spectrophotometry
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Simultaneous Measurement of Superoxide/Hydrogen Peroxide and NADH Production by Flavin-containing Mitochondrial Dehydrogenases
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Area of Science:

  • Microbiology
  • Bacterial Physiology
  • Biochemistry

Background:

  • Staphylococcus aureus is a major public health concern due to drug-resistant infections.
  • Its energetic metabolism and respiratory enzymes remain underexplored.
  • Adaptability to varying oxygen levels is key to S. aureus infections.

Purpose of the Study:

  • To identify, describe, and revise the monotopic quinone reductases in S. aureus.
  • To provide an integrated view of the S. aureus respiratory chain.
  • To elucidate the role of quinone reductases in bacterial adaptability.

Main Methods:

  • Bioinformatic analysis of S. aureus genome.
  • Identification and characterization of quinone reductase proteins.
  • Comparative analysis of respiratory chain components.

Main Results:

  • Eight monotopic quinone reductases were identified in S. aureus.
  • These enzymes play a critical role in connecting catabolic pathways to the respiratory chain.
  • The diversity of quinone reductases contributes to S. aureus's metabolic plasticity.

Conclusions:

  • Monotopic quinone reductases are essential for S. aureus's respiratory flexibility.
  • Understanding these enzymes offers insights into S. aureus's survival strategies.
  • This work provides a comprehensive view of S. aureus's respiratory chain components.