Oxidation phosphorylation

• Aerobic respiration stage 4: Oxidative phosphorylation takes place on the cristae of mitochondria.
• Part 1 During aerobic respiration stage 4: Oxidative phosphorylation, NAD/FAD is reduced, releasing H atoms which are split into protons (H+) and electrons (e-).
• Part 2 Electrons are transferred down the electron transport chain by redox reactions
• Part 3 The energy released by electrons during electron transferring during part 2 is used in the production of ATP from ADP + Pi, - chemiosmotic theory.
• Why is oxygen needed for the production of ATP on the cristae of the mitochondrion?

  • Oxygen = terminal electron acceptor for electrons passing along the ETC

  • The ETC releases the energy for the formation of (most) ATP (from ADP + P i )

  • No oxygen to accept them = electrons can’t be passed along the electron transport chain

  • The Krebs cycle and link reaction also stop in the absence of oxygen because NAD and FAD (converted from reduced NAD/FAD as they release their H atoms for the ETC,) cannot be produced
• Other respiratory substrates

  • Other respiratory substrates include the breakdown products of lipids and amino acids, which enter the Krebs cycle. For example:

  • Fatty acids from the hydrolysis of lipids are converted to Acetyl Coenzyme A

  • Amino acids from the hydrolysis of proteins are converted to intermediates in Krebs cycle
• Energy released by electrons used in the production of ATP from ADP + Pi (chemiosmotic theory)

  :a.Energy used by electron carriers to actively transport protons from the matrix to the intermembrane space

  b. Protons diffuse down an electrochemical gradient, via ATP synthase (embedded in the inner

  mitochondrial membrane) back into the matrix

  c. Releasing energy to combine ADP + Pi to ATP

  • In the matrix at the end of the electron transport chain, oxygen is the final electron acceptor –

  protons, electrons and oxygen combine to form water