Question

Fill in the blanks about each of the following sequential steps of the electron transfer chain (ETC) of the inner mitochondrial membrane.

a. The initial electron donor of the ETC is _______________, which hands its two electrons off to FMN, within Complex I.

b. Electrons from both Complex I and Complex II are ultimately donated to the same molecule, ____________.

c. Within Complex III, electrons from ubiquinol are ultimately donated to ______________, which then passes those electrons on to Complex IV.

d. ______________ is the final electron acceptor of the ETC.

e. The downhill movement of electrons through the ETC creates a proton gradient across the inner mitochondrial membrane. The _________________ subunit of the ATP synthase creates a channel that allows for the downhill movement of protons from the intermembrane space to the matrix.

f. The concomitant release of free energy drives the synthesis of ATP by the ____________ subunit of that same protein.

Answer 1

A. In electron transport chain initial electron donor is NADH. Complex I contain enxyme NADH dehydrogenase or NADH- coenzyme Q reductase contain FMN as prosthetic group. FMN accepts two electrons and a proton from NADH + H⁺ to from FMNH₂.

NADH + H⁺ + FMN----------> NAD⁺ + FMNH₂

B. Coenzyme Q or Ubiquinone( Q) accepts electron from Complex I and Complex II and transfer them to complex III. CoenzymeQ receive electrons from FMNH_{2 ,} FADH₂ of complex I and Complex II respectively and also succinate dehydrogenase.

C. Cytochrome c accepts electrons from ubiquinone. Ubiquinone(Q) gets reduced to ubiquinol (QH₂) and trannsfers the electrons to Ctyochrome c which transfers electron to complex IV. Cytochrome c can accept only one electron at a time.

D. Oxygen molecule(O₂) is the final electron acceptor of ETC. O₂ accepts electrons and gets to reduced to from H₂O.

E. Subunit C of F0 ATP synthase creates for H⁺ gradient. The rotation of sununit C allows the passage of H+ ions to matrix.

F. Beta subunit of F1 ATP synthase enzyme drives the ATP synthesis.