Target type: biologicalprocess
The transfer of electrons from succinate to ubiquinone that occurs during oxidative phosphorylation, mediated by the multisubunit enzyme known as complex II. [ISBN:0716731363]
The succinate to ubiquinone segment of the mitochondrial electron transport chain is a critical step in cellular respiration, responsible for generating a proton gradient that drives ATP synthesis. This process involves two key proteins: succinate dehydrogenase (SDH), also known as Complex II, and ubiquinone (Q).
Succinate dehydrogenase is an integral membrane protein embedded within the inner mitochondrial membrane. It functions as both a dehydrogenase, oxidizing succinate to fumarate, and a reductase, reducing ubiquinone to ubiquinol. This dual function is essential for linking the citric acid cycle to the electron transport chain.
Succinate, a product of the citric acid cycle, binds to the active site of SDH. The enzyme then catalyzes the removal of two electrons from succinate, converting it to fumarate. These electrons are transferred to an iron-sulfur cluster within SDH.
The electrons are then passed from the iron-sulfur cluster to ubiquinone, which is a small, mobile lipid-soluble molecule that acts as an electron carrier within the mitochondrial membrane. Ubiquinone accepts the electrons and becomes reduced to ubiquinol (QH2).
The transfer of electrons from succinate to ubiquinone is coupled with the translocation of protons from the mitochondrial matrix to the intermembrane space. This process is driven by the redox potential difference between succinate/fumarate and ubiquinone/ubiquinol.
The proton gradient generated by this process is essential for ATP synthesis by ATP synthase, which utilizes the electrochemical potential energy stored in the gradient to drive the phosphorylation of ADP to ATP.
In summary, the succinate to ubiquinone segment of the electron transport chain plays a crucial role in energy production by:
- Oxidizing succinate to fumarate in the citric acid cycle.
- Reducing ubiquinone to ubiquinol, which is a key electron carrier in the electron transport chain.
- Generating a proton gradient across the inner mitochondrial membrane, driving ATP synthesis.
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| Protein | Definition | Taxonomy |
|---|---|---|
| Succinate dehydrogenase [ubiquinone] flavoprotein subunit, mitochondrial | A succinate dehydrogenase [ubiquinone] flavoprotein subunit, mitochondrial that is encoded in the genome of human. [PRO:DNx] | Homo sapiens (human) |
| Compound | Definition | Classes | Roles |
|---|---|---|---|
| linezolid | acetamides; morpholines; organofluorine compound; oxazolidinone | antibacterial drug; protein synthesis inhibitor |