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Related Concept Videos

The Electron Transport Chain01:30

The Electron Transport Chain

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.
Inhibitors of the electron transport chain
Rotenone, a widely used pesticide, prevents electron transfer from Fe-S cluster to ubiquinone or Q in...
Electron Transport Chain: Complex III and IV01:43

Electron Transport Chain: Complex III and IV

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...
Pyruvate Oxidation01:15

Pyruvate Oxidation

After glycolysis, the charged pyruvate molecules enter the mitochondria via active transport and undergo three enzymatic reactions. These reactions ensure that pyruvate can enter the next metabolic pathway so that energy stored in the pyruvate molecules can be harnessed by the cells.
First, the enzyme pyruvate dehydrogenase removes the carboxyl group from pyruvate and releases it as carbon dioxide. The stripped molecule is then oxidized and releases electrons, which are then picked up by NAD+...
Electron Transport Chain: Complex I and II01:46

Electron Transport Chain: Complex I and II

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...
Respiration Pathways01:26

Respiration Pathways

Cellular respiration is a fundamental metabolic process that enables organisms to generate energy from organic molecules. One of its central pathways is the tricarboxylic acid (TCA) cycle, also known as the Krebs cycle, which plays a crucial role in energy production and biosynthetic processes.Conversion of Pyruvate to Acetyl-CoAThe pyruvate generated from glycolysis undergoes oxidative decarboxylation by the pyruvate dehydrogenase complex, producing acetyl-CoA, one molecule of NADH, and one...
Electron Transport Chains01:28

Electron Transport Chains

The final stage of cellular respiration is oxidative phosphorylation that consists of two steps: the electron transport chain and chemiosmosis. The electron transport chain is a set of proteins found in the inner mitochondrial membrane in eukaryotic cells. Its primary function is to establish a proton gradient that can be used during chemiosmosis to produce ATP and generate electron carriers, such as NAD+ and FAD, that are used in glycolysis and the citric acid cycle.
The ETC is comprised of...

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Updated: May 9, 2026

Mitochondrial Respiration Quantification in Yeast Whole Cells
07:15

Mitochondrial Respiration Quantification in Yeast Whole Cells

Published on: November 8, 2024

Mitochondrial respiration without ubiquinone biosynthesis.

Ying Wang1, Siegfried Hekimi

  • 1Department of Biology, McGill University, MontrĂ©al, Quebec, Canada H3A 1B1.

Human Molecular Genetics
|July 13, 2013
PubMed
Summary

Primary ubiquinone (UQ) deficiency impairs mitochondrial function. Engineered models show that isoprenoid side chain UQ analogues, not alkyl ones, effectively rescue UQ deficiency, with dietary UQ10 showing therapeutic potential.

Area of Science:

  • Mitochondrial biochemistry
  • Cellular respiration
  • Metabolic disorders

Background:

  • Ubiquinone (UQ), or coenzyme Q, is vital for mitochondrial electron transport.
  • Primary UQ deficiency causes severe, debilitating conditions.
  • Mclk1 (Coq7) is essential for UQ biosynthesis.

Purpose of the Study:

  • Investigate pathogenic effects of UQ deficiency using conditional Mclk1 knockout models.
  • Assess therapeutic potential of UQ analogues for UQ deficiencies.
  • Determine the impact of UQ depletion on mitochondrial respiration and cellular viability.

Main Methods:

  • Engineered conditional Mclk1 knockout mouse models (cell and liver-specific).
  • Assessed mitochondrial respiration and viability in UQ-deficient cells.

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  • Tested efficacy of various UQ analogues (alkyl vs. isoprenoid side chains) and Vitamin K2.
  • Evaluated the effect of liver-specific Mclk1 loss on respiratory function and UQ content.

    • Main Results:

    • Mclk1 knockout cells survive without UQ, accumulating DMQ9, which inefficiently supports respiration.
    • Isoprenoid side chain UQ analogues, unlike alkyl ones (e.g., idebenone), efficiently rescued respiratory deficiency.
    • Vitamin K2 showed no efficacy in UQ-deficient mouse cells.
    • Liver-specific Mclk1 loss caused mild respiratory impairment despite significant UQ depletion, indicating a nonlinear relationship between UQ content and respiratory capacity.
    • Dietary UQ10 effectively rescued liver UQ deficiency and electron transport deficits.

    Conclusions:

    • UQ biosynthesis is dispensable for cell viability but crucial for efficient mitochondrial respiration.
    • Isoprenoid side chain analogues are superior to alkyl analogues for rescuing UQ deficiency.
    • Mitochondrial respiratory capacity is robust to UQ depletion, showing a nonlinear dependence.
    • Exogenous UQ10 can rescue severe endogenous UQ deficiency in the liver.