oxidative phosphorylation and chemiosmosis

• the final stage of aerobic respiration is oxidative phosphorylation, the production of ATP in the presence of oxygen.
• Oxidative phosphorylation takes place in the mitochondria. it involves electron carrier protein arranged in chains called electron transport chains and they are embedded in the inner mitochondrial membrane- in addition to a process called chemiosmosis.
• The folded cristae give a large surface area for the electron carrier proteins and the atp synthase enzymes:

  1. reduced NAD and FAD are reoxidized when they deliver their hydrogen atoms to the electron tran sport chain.
  2. the hydrogen atoms released from the reduced co enzymes are split into protons and electrons.
  3. the protons go into the solution in the mitochondrial matrix
• the electrons from the hydrogen atoms pass along the chain of electron carriers. each electron carrier protein has an iron atom at its core- these ions can gain an electron becoming reduced Iron 2 +
• The reduced Iron ion can donate the electron to the iron ion in the next electron carrier in the chain, becoming reoxidized to iron 3+. As electrons pass along the chain, some of their energy is used to pump proteins across the inner mitochondrial membrane into the intermembrane space.
• As the protons accumulate into the intermembrane space, a proton gradient forms across the membrane. The proton gradient generates a chemiosmotic potential that is also known as a proton motive force- they are a source of potential energy . And ATP is made using this energy from the proton motive force.
• Protons cannot easily diffuse through the lipid bilayer of the mitochondrial membrane as the outer membrane has a low degree of permeability to protons and the inner membrane is impermeable to protons.~
• However, protons can diffuse through the protein channels associated with ATP synthase enzymes that are in the inner membrane. ~
• As protons diffuse down their concentration gradfient through ATP synthase channels, the flow of protons causes a conformational change in the ATP synthase enzyme- this allows Adeno di phosphate (ADP) and an inorganic phosphate group to combine and form ATP. this flow of protons is called chemiosmosis.
• oxygen is the final electron acceptor. it combines with electrons coming off the electron transport chain and with protons, diffusing down the ATP synmtha see channel which forms water.
• what is the net gain of ATP in glycolysis?

  2 molecules
• What is the net gain of ATP per glucose molecule in the link reaction?

  0
• What is the net gain of ATP per glucose molecule in the kreb's cycle?

  2
• What is the net gain of ATP per glucose molecule in oxidative phosphorylation?

  28