oxidative phosphorylation and chemiomostic theory

• electron transport chain and oxidative phosphorylation by chemiosmosis

  
• oxidative phosphorylation


  • production of ATP in the presence of oxygen
  • chemisomotic theory
  • both reactions take place on the inner membrane of the mitochondria - cristae
• theory of chemiosmosis 


  • states that the energy in a chemical gradient established by electron movement is used to generate ATP

  evidence includes

  • proton gradient across the inner membrane can be measured as it corresponds to a pH gradient
  • isolated ATP synthase enzymes can produce ATP using a proton gradient even if no electron transport is occurring
  • chemicals that block the ETC inhibit the formation of a proton gradient and prevent ATP synthesis
• oxidative phosphorylation takes place in the mitochonria
• chemiosmosis

  1. reduced NAD and reduced FAD are reoxidised when they deliver their hydrogen atoms to electron transport chain
  2. hydrogen atoms released from the reduced coenzymes split into protons and electrons
  3. protons go into solution in mitochondrial matrix
• formation of ATP in presence of oxygen = oxidative phosphorylation
• efficiency of aerobic respiration

  • theoretical yield of 32 ATPs for each glucose molecule is rarely achieved - respiration is only 32% efficient
  • some protons leak across the mitochondrial membrane, so not all are available to generate ATP via chemiosmosis
  • some ATP is used up moving pyruvate into the mitochondria by active transport
  • some ATP is used up moving hydrogen from reduced NAD made during glycolysis into the mitochondria
  • some energy is lost as heat. This heat helps to maintain a suitable body temperature for enzyme controlled reactions
• ATP yield per molecule of glucose at each stage of respiration