Oxidative Phosphorylation

• In mitochondrial membrane (cristae), about protons and electrons and relies on chemiosmosis, it is process where energy carried by electrons from reduced coenzymes is used to make ATP in presence of oxygen
• Aims to synthesise ATP (most ATP from aerobic respiration is made here) and re-oxidise (NADH + H+) and FADH2 so that the processes of glycolysis, link reaction and Krebs’ cycle can continue
• Electron gradient makes a chemical gradient and proton (H^+) movement down concentration gradient releases energy used to create ATP from ADP + Pi
• Depends on proton concentration gradient creation; energy comes from high-energy (excited) electrons and raised to higher energy level in 2 ways: Photosynthesis (electrons in chloroplast pigment molecules are excited by absorbing sunlight) and respiration (high energy electrons release when glucoses’ chemical bonds are broken in mitochondria)
• Diagram 1

  A) reduced NAD

  B) reduced FAD

  C) reduced

  D) NAD

  E) FAD

  F) Oxidised NAD

  G) 2e^-

  H) carriers

  I) ATP

  J) ADP + P_i

  K) ATP

  L) 2e^-

  M) 2H^+

  N) 1/2O_2

  O) H_2O

  P) electrons

  Q) hydrogen

  R) ions

  S) water

  
• Diagram 2:
• Diagram 2:

  Cofactors accept and donate electrons as iron in haem group can be reduced to Fe^2+ and oxidised to Fe^3+

  A) matrix

  B) Outer Membrane

  C) Inner Membrane

  D) Intermembrane Space

  E) Krebs cycle

  F) link reaction

  G) ATP Synthase

  H) Intermembrane Space

  I) proton gradient

  J) Inner Membrane

  K) inner

  L) electron

  M) protons

  N) Intermembrane Space

  
• Takes place in folded inner membrane of mitochondria, cristae, excited electrons are taken to electron transport chain (ETC) embedded in inner mitochondrial membrane by reduced coenzymes NAD and FAD
• ETC: Series of membrane proteins with iron ions in haem groups, positioned close enough for electron transfer; iron reduces (when electron gained), oxidizes (when lost)
• Role of oxygen: Final electron acceptor combines with electrons at end of ETC and H^+ from reduced NAD and FAD to make water; 4H^+ + 4e^- + O_2 → 2H_2O, it enables more electrons to move down ETC and ATP synthesis, inhibited by cyanide and carbon monoxide, they block respiratory process and halt Krebs cycle
• ATP Synthase/Stalked Particle: Protons flow down proton gradient through ATP synthase (chemiosmosis); this flow or proton motive force drives rotation of part of the enzyme so that ADP+Pi → ATP

  A) fraction

  B) molecule

  C) oligomycin

  D) proton

  E) Base

  F) Stalk

  G) axle

  H) Headpiece

  I) Inner mitochondrial membrane

  J) Stator

  
• Chemiosmotic theory evidence: Measure proton gradient across inner membrane; corresponds to pH gradient, ATP synthase produces ATP using proton gradient (without electron transport) Chemicals blocking ETC prevent a proton gradient and ATP synthesis