Question

What is the biochemical function of the respiratory chain?

Answer 1

• Respiratory chain is also referred to as the electron transport chain. The reaction in the respiratory chain is oxidative phosphorylation.
• Electrons are transported across various components of electron transport chain (ETC), resulting in series of oxidation-reduction reactions within the membrane bound complexes in mitochondria (complex I, II, III, IV).
• The final complex being the ATP synthase.

Complex I: NADH dehydrogenase:

Complex II: Succinate dehydrogenase

Complex III: Ubiquinol cytochrome C oxidoreductase

Complex IV: Cytochrome C oxidase

Complex V: ATP synthase.

• NADH and FADH2 are electron donors; their oxidation creates high concentration energy from electrons.
• This energy is used to pump proton from matrix to inter membrane space.
• Flow of protons creates and electrochemical gradient, which is used to generate ATP.
• The enzyme ATP synthase, is responsible for conversion of transmembrane proton potential difference into “energy currencies of cells” in form of ATP. ATP synthase have two components, that functions as motors, called F0 and F1, to form F0F1 complex.

• F0F1 ATPase is involved in oxidative phosphorylation or electron transport phosphorylation. Under aerobic condition, phosphorylation of ADP to ATP is carried out by proton motive force.

  Under anaerobic or fermentative condition, F0F1 ATPase, carries out proton expulsion, in expense of ATP hydrolysis.