oxidative phosphorylation

• oxidative phosphorylation is the process where the energy carried by electrons from reduced coenzymes (NADH and FADH) is used to make ATP - the whole point of the previous stages is to make NADH and FADH for the final stage
• oxidative phosphorylation involves the electron transport chain and chemiosmosis
• 1. hydrogen atoms are released from NADH and FADH as they are oxidised to NAD and FAD - the hydrogen atoms split into electrons e- and protons H+
• 2. the electrons move down the electron transport chain (made up of electron carriers) losing energy at each carrier
• 3. this energy is used by the electron carriers to pump protons from mitochondrial matrix into the intermembrane space (space between the inner and outer mitochondrial membranes)
• 4. the concentration of protons is now higher in the intermembrane space than in the mitochondrial matrix - this forms an electrochemical gradient (a concentration gradient of ions)
• 5. protons then move down the electrochemical gradient, back across the inner mitochondrial membrane and into the mitochondrial matrix via ATP synthase (embedded in the inner mitochondrial membrane)

  this movement drives the synthesis of ATP from ADP and Pi
• 6. this process of ATP production driven by the movement of H+ ions across a membrane (due to electrons moving down an electron transport chain) is called chemiosmosis (described by the chemiosmotic theory
• 7. in the mitochondrial matrix, at the end on the transport chain, the protons, electrons and oxygen (from the blood) combine to form water

  oxygen is said to be the final electron acceptor
• aerobic resp and ATP:

  oxidative phosphorylation makes ATP using energy from the reduced coenzymes - 2.5 ATP are made from each NADH and 1.5 from each FADH
• the regenerated coenzymes from the electron transport chain are reused in the Krebs cycle
• the job of a carrier is to transfer electrons

  when a carrier receives electrons it is reduced and when it passes on electrons it becomes oxidised again
• a cell can make 32 ATP from 1 molecule of glucose in aerobic respiration: one molecule of glucose produces 2 pyruvate so the link and Krebs happen 2x
• glycolysis - 2 molecules ATP produced - 2

  glycolysis - 2 NADH - 2 x 2.5 = 5 ATP produced

  link x2 - 2 NADH - 2 x 2.5 ATP

  krebs 2X - 2 ATP

  Krebs 2X - 6 NADH - 6 X 2.5 = 15

  Krebs 2x - 2 FADH - 2 x 1.5 = 3

  = 32 ATP