1. Chapter 13 &14 Energy Generation in Mitochondria

2. Generation of Energy Millions of years ago there was no O 2 available for oxidative phosphorylation to occur Organisms produced energy from fermentation, still see this today As O 2 became available, a more efficient method of energy production developed –Based on the transfer of e - along the membrane

3. Glycolysis – sugar breaking rxn Each step of rxns mediated by specific enzymes ATP input necessary to get process started Glycolysis occurs in the cytosol – anaerobic (no oxygen necessary)

4. Organisms Energy Source Small amount of ATP from glycolysis in the cytosol of cells Majority made by a membrane based process in 2 stages –Stage 1 – e - transport chain e - transferred along e - carriers in the membrane –Stage 2 – flow of H + down an electrochemical gradient to produce ATP Use a complex called ATP synthase

5. Stage 1 NADH (from the Kreb’s cycle) brings in the e - and transfers them to the carrier molecules The e - moves down the chain and looses energy at each step – as this happens, H + are pumped across the membrane This creates an electro- chemical gradient across the membrane

6. Stage 2 The electrochemical gradient is a form of stored energy – it has the potential to do work The H + can now move down the gradient and return to the other side of the membrane thru ATP synthase – in this process, generates ATP from ADP and P i

7. Chemiosmotic Coupling Once called the chemiosmotic hypothesis –Chemi from making ATP, osmotic because of crossing the membrane Now known as chemiosmotic coupling

8. Proton Pumping Many molecules can supply the e - - carbohydrates and fatty acids O 2 ultimate e - acceptor producing H 2 O as waste

9. Movement of Electrons

10. Mitochondria Produce most of a cells ATP – acetyl groups in the Kreb’s cycle producing CO 2 and NADH NADH donates the e - to the electron transport chain and becomes oxidized to NAD + e - transfer promotes proton pump and ATP synthesis in process called oxidative phosphorylation Cells that require large amounts of energy such as the heart have large numbers of mitochondria

11. Oxidative Phosphorylation

12. Mitochondria Contain their own copies of DNA and RNA along with transcription and translation system (ribosomes) Are able to regenerate themselves without the whole cell undergoing division Shape and size dependent on what the cell’s function is

13. Mitochondria Double membrane creates 2 spaces –Matrix – large internal space –Intermembrane space – between the membranes Outer membrane Inner membrane

14. Page 457

15. Inner Membrane Inner membrane is the site of the e - transport chain, across which the proton pump occurs and contains ATP synthase Inner membrane is highly folded – called cristae – increasing the surface area on which the above reactions can take place

16. High Energy e - Mitochondria use pyruvate and fatty acids and convert it to acetyl CoA in the matrix Citric acid cycle generates NADH and FADH 2 which carry the e - to the electron transport chain

17. Summary – MUST KNOW

18. Location of H +

19. 4 Complexes in Membrane

20. Electron Transport Chain Resides in the inner mitochondrial membrane – also called respiratory chain 15 proteins involved in the chain – grouped in 3 large respiratory enzyme complexes –NADH dehydrogenase complex –Cytochrome b-c 1 complex –Cytochrome oxidase complex Pumps protons across the membrane as e - are transferred thru them

21. Respiratory Enzyme Complexes

22. Proton Gradient e - transfer is an oxidation/reduction reaction NADH has high-energy e - has a low electron affinity so the e - is readily passed to NADH dehydrogenase and so on down the chain Each transfer couples the energy released with the uptake of a H + from the matrix to the intermembrane space setting up the electrochemical gradient

23. Proton Gradient Gradient of proton (H + ) concentration across the inner mitochondrial membrane – a pH gradient with the pH in the matrix higher than in the intermembrane space Proton pumping also generates a membrane potential – matrix side is negative and intermembrane space is positive

24. Electrochemical Gradient

25. Oxidative Phosphorylation ATP synthase is the protein complex responsible for making ATP by creating a path for H + thru the membrane ATP synthase is an enzyme

26. ATP Synthase Multisubunit protein responsible for making ATP

27. Summary

28. Bidirectional Pump

29. Coupled Transport Can Move Other Molecules

30. Oxidation of Sugar and Fats

31. Protons In H 2 O H + can move along the H-bonds in H 2 O Dissociating from one molecule to associate with the next one

32. Transfer of H + and e - The transfer of an e - sets up a negative charge which is rapidly neutralized by adding a H +, the molecule is reduced Reverse is true when things are oxidized

33. e - Transport Chain

34. Redox Potential Redox = oxidation-reduction reactions Depends on the affinity for electrons of the molecules involved in each reaction Redox pairs – two molecules such as NADH and NAD + - NADH is a strong electron donor (oxidizing agent) while NAD + is a weak electron acceptor (reducing agent) Redox Potential – a measure of the tendency of a given system to donate or accept electrons

35. Versatile Electron Carriers The respiratory complexes are made up of a metal ion bound to a protein molecule The metal ion is responsible for the movement of the e -, skipping from one ion to another Ubiquinone, a hydrophobic molecule, that can move electrons without being bound to a protein

36. Quinone Electron Carriers Can carry either 1 or 2 e - and picks up 1 H + for each e -

37. Other e - Carriers Dehydrogenation complex –Flavin group –Iron-sulfur centers – carry 1 e - at a time Cytochrome b-c 1 and cytochrome oxidase complexes –Proteins that contain a heme group that can accept an e - –Cytochromes are colored due to the Fe