Question

Explain how complex I move Hydrogens out of the mitochondrial matrix when transferring electrons to Coenzyme Q.

Answer 1

Answer: Electron transport chain in the mitochondria consists of a series of complexes (complex I-IV) that transfers electrons from donors to acceptors through oxidation-reduction (Redox) reactions. This electron transfer is coupled with transfer of protons (H+) from mitochondrial matrix to intermembranal space, creating a proton gradient that leads to ATP sysnthesis via oxidative phosphorylation.

Complex I also known as NADH coenzyme Q reducatse or NADH ubiquinone oxireducatse oxidizes NADH (derived from Krebs cycle) to NAD+ by transferring two electrons to FMN (Flavin mononucleotide) and reducing it to FMNH2.

FMNH2 is then oxidized by transfering electron to iron-sulphur cluster (Fe-S). Fe-S cluster then transfer electrons to ubiquinone or Coenzyme Q in a two one electron steps. Transfer of one electron forms semiquinone form of Coenzyme Q. Finally, transfer of second electron to semiquinone reduces it to ubiquinol (QH2). For every electrons transfered to Coenzyme Q, two protons (H+) are translocated to intermembranal space from mitochondrial matrix. Hence, for a total of two electrons transfered, four protons are translocated to intermembranal space.