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Related Concept Videos

Cofactors and Coenzymes01:24

Cofactors and Coenzymes

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Enzymes are proteins made of amino acids. The functional group of each constituent amino acid catalyzes a wide variety of chemical reactions via ionic interactions or acid-base reactions. However, amino acids cannot catalyze oxidation-reduction and group transfer reactions and need to be aided by non-protein components called cofactors. Cofactors are also referred to as the chemical teeth of an enzyme.
Cofactors can be metallic ions or organic molecules called coenzymes. These types of helper...
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Electron Transport Chain: Complex I and II01:46

Electron Transport Chain: Complex I and II

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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.
ROS generation is regulated and maintained at moderate levels necessary...
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Role of Reduced Coenzymes NADH and FADH₂01:29

Role of Reduced Coenzymes NADH and FADH₂

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The energy released from the breakdown of the chemical bonds within nutrients can be stored either through the reduction of electron carriers or in the bonds of adenosine triphosphate (ATP). In living systems, a small class of compounds functions as mobile electron carriers, molecules that bind to and shuttle high-energy electrons between compounds in pathways. The principal electron carriers that will be considered originate from the B vitamin group and are derivatives of nucleotides; they are...
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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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Electron Transport Chain: Complex III and IV01:43

Electron Transport Chain: Complex III and IV

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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...
7.4K
Cooperative Allosteric Transitions01:58

Cooperative Allosteric Transitions

7.9K
Cooperative allosteric transitions can occur in multimeric proteins, where each subunit of the protein has its own ligand-binding site. When a ligand binds to any of these subunits, it triggers a conformational change that affects the binding sites in the other subunits; this can change the affinity of the other sites for their respective ligands. The ability of the protein to change the shape of its binding site is attributed to the presence of a mix of flexible and stable segments in the...
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Related Experiment Video

Updated: Jun 26, 2025

Inner Mitochondrial Membrane Sensitivity to Na+ Reveals Partially Segmented Functional CoQ Pools
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Inner Mitochondrial Membrane Sensitivity to Na+ Reveals Partially Segmented Functional CoQ Pools

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Understanding coenzyme Q.

Ying Wang1, Noah Lilienfeldt1, Siegfried Hekimi1

  • 1Department of Biology, McGill University, Montreal, Quebec, Canada.

Physiological Reviews
|May 9, 2024
PubMed
Summary

Coenzyme Q (CoQ), or ubiquinone, is vital for cellular redox balance and mitochondrial electron transport. Its deficiency, common in aging and disease, poses challenges for supplementation therapy.

Area of Science:

  • Biochemistry and Molecular Biology
  • Cellular Metabolism
  • Mitochondrial Function

Background:

  • Coenzyme Q (CoQ), also known as ubiquinone, is a hydrophobic molecule essential for cellular redox balance.
  • It plays a critical role in the mitochondrial electron transport chain (ETC) and other cellular processes.
  • CoQ's structure is conserved across species, highlighting its fundamental biological importance.

Purpose of the Study:

  • To review the multifaceted roles of CoQ, including its function in the ETC, prooxidant activity, and antioxidant mechanisms.
  • To examine CoQ biosynthesis, challenges posed by its hydrophobicity, and the consequences of CoQ deficiency.
  • To discuss the therapeutic potential and difficulties of CoQ supplementation for deficiencies.

Main Methods:

Keywords:
CoQCoQ deficiencycoenzyme Qmitochondrial diseaseubiquinone

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  • Literature review of Coenzyme Q (CoQ) functions, biosynthesis, and deficiency states.
  • Analysis of CoQ's role in electron transport, redox balance, and reactive oxygen species generation.
  • Examination of primary and secondary CoQ deficiency conditions and supplementation strategies.

    • Main Results:

    • CoQ is central to cellular redox homeostasis and mitochondrial energy production.
    • CoQ exhibits dual roles as an antioxidant and a prooxidant, influencing reactive oxygen species.
    • CoQ deficiency, both primary (genetic) and secondary (pathological), has significant health implications.

    Conclusions:

    • CoQ is indispensable for cellular function, with complex roles in redox biology and energy metabolism.
    • CoQ deficiency is linked to various pathologies, including mitochondrial disorders and aging.
    • Alleviating CoQ deficiency through supplementation is challenging due to its hydrophobic nature and complex biology.