What compound receives electrons from NADH?
FMN
ubiquinone
cytochrome c1
oxygen
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The Correct Answer and Explanation is :
The compound that receives electrons from NADH is ubiquinone, also known as coenzyme Q. This process occurs within the mitochondrial electron transport chain, a critical component of cellular respiration.
Electron Transport Chain Overview:
The electron transport chain (ETC) is a series of protein complexes and other molecules embedded in the inner mitochondrial membrane. Its primary function is to transfer electrons from electron donors like NADH to electron acceptors such as oxygen, facilitating the production of adenosine triphosphate (ATP) through oxidative phosphorylation.
Role of NADH and Ubiquinone:
NADH, generated during glycolysis and the citric acid cycle, donates electrons to the ETC. These electrons enter Complex I (NADH: ubiquinone oxidoreductase), where NADH is oxidized to NAD⁺, and the electrons are transferred to flavin mononucleotide (FMN), reducing it to FMNH₂. The electrons then pass through a series of iron-sulfur (Fe-S) clusters within Complex I, ultimately reaching ubiquinone. Ubiquinone accepts these electrons, becoming reduced to ubiquinol (QH₂). This reduction of ubiquinone is a crucial step in the ETC, as it links the initial electron donors to the subsequent complexes.
Subsequent Steps in the Electron Transport Chain:
After ubiquinone is reduced to ubiquinol, it diffuses through the inner mitochondrial membrane to Complex III (cytochrome bc₁ complex). Here, ubiquinol donates electrons to cytochrome c, a small, soluble electron carrier. Cytochrome c then transfers electrons to Complex IV (cytochrome c oxidase), where they are ultimately transferred to molecular oxygen (O₂), reducing it to water (H₂O). This final electron transfer is coupled with the pumping of protons (H⁺) across the inner mitochondrial membrane, contributing to the proton gradient that drives ATP synthesis.
Conclusion:
In summary, ubiquinone is the compound that receives electrons from NADH in the electron transport chain. This electron transfer is essential for the generation of the proton gradient used in ATP production, highlighting the importance of ubiquinone in cellular energy metabolism.
For a visual explanation, you might find the following video helpful: