Which of the following regulate oxidative phosphorylation under hypoxic conditions?

Which of the following regulate oxidative phosphorylation under hypoxic conditions? Pyruvate dehydrogenase (PDH) kinase phosphorylates PDH, inactivating it and reducing the availability of electron carriers to the electron transport chain. I decreases below 6.5 and IF1 exists as a stable dimer capable of inhibiting the ATPase activity of ATP synthase. ATP synthase converts ATP to ADP, raising [ADP] to increase the rate of oxidative phosphorylation. HIF-1 replaces a subunit of Complex IV of the electron transport chain with a subunit that is more efficient under hypoxic conditions. The protein inhibitor IF1 binds one ATP synthase molecule and inhibits its activity.

Answer

2,4,5
1.

• 
  one way to guard against ROS is regulating pyruvate dehydrogenase
  (delivers acetyl-CoA to the citric acid cycle). Low O2 conditions
  cause PDH kinase to phosphorylate mitochondrial PDH, inactivating
  it and slowing delivery of FADH2 and NADH from the citric acid
  cycle to the respiratory chain

• 
  when cell is hypoxic, electron transfer to oxygen slows and so does
  pumping of protons
• 
  proton motive force collapses and ATP synthase could operate in
  reverse,hydrolyzingATP to pump protons
  outward
• 
  this is prevented byIF1protein, which binds ATP
  synthase molecules and inhibits ATPase activity
• 
  only active at pH 6.5

• 
  an other way to prevent ROS is by replacing one subunit of complex
  IV, which is better suited in low O2 conditions
• 
  both defense mechanisms are mediated by HIF-1(hypoxia inducible
  factor)