Oxidative phosphorylation

• Where is the ETC found in oxidative phosphorylation?

  In the membranes of the cristae of the mitochondria
• what is the matrix of a mitochondria composed of?

  proteins, lipids and traces of DNA
• what do cristae have attached which helps them with the ETC?

  proteins
• what are enzymes in the mt matrix used for

  • link reaction
  • Krebs cycle
• Where does the energy used to generate chemiosmosis come from?

  energy released during redox reactions as electron carriers are oxidised and reduced
• how are NAD and FAD oxidised and reduced by electrons?

  • they are proteins with a haem prosthetic group
  • haem group is (Fe2+) and it can be oxidised to Fe3+ and back again to Fe2+ as it receives and donates electrons
• What is the sequence of electron transfer from one carrier to the next (ETC) catalysed by?

  Enzyme oxidoreductase
• how many complexes accept electrons in the ETC?

  3

  • NADH dehydrogenase
  • protein cytochrome complex
  • cytochrome oxidase complec
• how is chemiosmosis able to take place?

  • each of the three complexes in the chain acts as a proton pump
  • use energy from the electrons to drive the protons from the inner mt matrix into the intermembranal space
  • Proton conc Grad/electrochemical Grad set up across the inner mt membrane
  • Acts as a store of energy which can be released if protons are allowed to pass back into the mt matrix through protein channel ATP synthase

  
• how do protons pass back into the mitochondrial matrix?

  • facilitated diffusion
  • through cotransporter protein ATP synthase
• how is ATP synthesised as a result of the ETC?

  • energy from chemiosmosis (as the protons reenter the mt matrix)
  • catalysed by ATPsynthase
• what happens at the end of the ETC?

  • protons and electrons recombine with oxygen (final electron acceptor) to produce water
  • catalysed by enzyme cytochrome oxidase
• State the sources of energy needed for chemiosmosis to take place and for ATP to be synthesised

  • Chemiosmosis- requires energy from the movement of electrons across ETC
  • ATP synthesis- requires energy from chemiosmosis
• true or false? the energy released from forming the bonds to produce water at the end can be used to synthesise ATP

  FALSE- heat released in the exothermic reaction would just raise the temp of the cell
• describe the components within a mitochondrion and state their functions

  • outer mitochondrial membrane- separates mitochondrion from the rest of the cell, creating a compartment with ideal conditions for aerobic respiration (compartmentalisation)
  • inner mitochondrial membrane- contains ETCs and ATP synthase
  • cristae- increase the surface area available for oxidative phosphorylation
  • matrix- contains enzymes for krebs cycle and link reaction, contains mt DNA
  • inter-membranal space- protons pumped into this space by ETC. Space is small so concentration builds up quick

  
• describe the sequence of events taking place in oxidative phosphorylation

  • reduced NAD and FAD arrive from the krebs cycle with protons and electrons
  • protons dissociate along with high energy electrons
  • electrons enter ETC and reduce electrons carriers as they flow along the chain
  • the electron carriers use the energy from this to drive protons from the mitochondrial matrix to the inter-membranal space
  • protons diffuse back down into the matrix through ATP synthase
  • This provides ATP synthase with the energy to form ATP
  • oxygen accepts electrons at the end of the chain along with 2 hydrogens to form water. ETC cannot operate unless oxygen is present

  
• true or false? the hydrogens attached to NAD and FAD can be released and bind directly to oxygen without chemiosmosis

  TRUE- but energy released from this would not synthesise ATP and just raise the temperature of the cell
• name an intermediate that is able to phosphorylate ADP (synthesise ATP) by substrate phosphorylation, apart from triose bisphosphate

  creatine phosphate