Making Energy: ATP - A Short-Term Energy Storage Molecule

1. Making energy! ATP The pointis to makeATP!

2. The energy needs of life • Organisms are endergonic systems • What do we need energy for? • synthesis • building biomolecules • reproduction • movement • active transport • temperature regulation

3. Where do we get the energy from? • Work of life is done by energy coupling • use exergonic (catabolic) reactions to fuel endergonic (anabolic) reactions energy + + energy + +

4. Living economy • Fueling the body’s economy • eat high energy organic molecules • food = carbohydrates, lipids, proteins, nucleic acids • break them down • catabolism = digest • capture released energy in a form the cell can use • Need an energy currency • a way to pass energy around • need a short term energy storage molecule ATP

5. high energy bonds ATP • Adenosine Triphosphate • modified nucleotide • nucleotide =adenine + ribose + Pi AMP • AMP + Pi ADP • ADP + Pi ATP • adding phosphates is endergonic

6. O– O– O– O– O– O– O– O– P P P P P P P P –O –O –O O– O– O– –O –O –O O– O– O– –O –O O– O– O O O O O O O O How does ATP store energy? • Each negative PO4 more difficult to add • a lot of stored energy in each bond • most energy stored in 3rd Pi • 3rd Pi is hardest group to keep bonded to molecule • Bonding of negative Pi groups is unstable • spring-loaded • Pi groups “pop” off easily & release energy AMP ADP ATP Instability of its P bonds makes ATP an excellent energy donor

7. O– O– O– O– P P P P –O O– –O O– –O –O O– O– O O O O How does ATP transfer energy? 7.3energy • ATP  ADP • releases energy • ∆G = -7.3 kcal/mole • can fuel other reactions • Phosphorylation • released Pi can transfer to other molecules • destabilizing the other molecules • enzyme that phosphorylates = kinase + ADP ATP

8. enzyme + + H H H H H H H H H2O C C C C C C C C OH OH HO HO O O + H ATP ADP + C H H P HO OH H C C + + Pi C P An example of Phosphorylation… • Building polymers from monomers • need to destabilize the monomers • phosphorylate! +4.2 kcal/mol “kinase”enzyme -7.3 kcal/mol -3.1 kcal/mol

9. P ATP C 2 hexokinase C 2 ADP phosphofructokinase H C P Another example of Phosphorylation… • The first steps of cellular respiration • beginning the breakdown of glucose to make ATP glucose C-C-C-C-C-C fructose-1,6bP P-C-C-C-C-C-C-P DHAP P-C-C-C G3P C-C-C-P

10. + P ATP / ADP cycle Can’t store ATP • too reactive • transfers Pi too easily • only short term energy storage • carbohydrates & fats are long term energy storage ATP respiration 7.3 kcal/mole ADP A working muscle recycles over 10 million ATPs per second

11. Thepoint is to makeATP! Cells spend a lot of time making ATP!

12. H+ H+ H+ H+ H+ H+ H+ H+ rotor rod + P catalytic head H+ ATP synthase • Enzyme channel in mitochondrial membrane • permeable to H+ • H+ flow down concentration gradient • flow like water over water wheel • flowing H+ cause change in shape of ATP synthase enzyme • powers bonding of Pi to ADPADP + Pi ATP ADP ATP But… How is the proton (H+) gradient formed?

13. That’s the rest of mystory! Any Questions?

14. Cellular Respiration STAGE 1: Glycolysis

15. Glycolysis • Breaking down glucose • “glyco – lysis” (splitting sugar) • most ancient form of energy capture • starting point for all cellular respiration • inefficient • generate only2 ATP for every 1 glucose • in cytosol • why does that make evolutionary sense? glucose      pyruvate 6C 3C 2x

16. Evolutionary perspective • Life on Earth first evolved withoutfree oxygen (O2) in atmosphere • energy had to be captured from organic molecules in absence of O2 • Organisms that evolved glycolysis are ancestors of all modern life • all organisms still utilize glycolysis

17. 2 NAD+ 2 NADH 4 ADP 4 ATP Overview glucose C-C-C-C-C-C activationenergy 2 ATP • 10 reactions • convert 6C glucose to two 3C pyruvate • produce 2 ATP & 2 NADH 2 ADP fructose-6P P-C-C-C-C-C-C-P DHAP P-C-C-C PGAL C-C-C-P pyruvate C-C-C

18. Glycolysis summary endergonic invest some ATP exergonic harvest a little more ATP & a little NADH

19. 1st half of glycolysis (5 reactions) • Glucose “priming” • get glucose ready to split • phosphorylate glucose • rearrangement • split destabilized glucose PGAL

20. 2nd half of glycolysis (5 reactions) • Oxidation • G3P donates H • NAD  NADH • ATP generation • G3P  pyruvate • donates P • ADP  ATP

21. OVERVIEW OF GLYCOLYSIS 1 2 3 6-carbon glucose (Starting material) ATP 2 P P P P 6-carbon sugar diphosphate 6-carbon sugar diphosphate P P P P 3-carbon sugar phosphate 3-carbon sugar phosphate 3-carbon sugar phosphate 3-carbon sugar phosphate NADH NADH 2 ATP 2 ATP 3-carbon pyruvate 3-carbon pyruvate Cleavage reactions.Then, the six-carbon molecule with two phosphates is split in two, forming two three-carbon sugar phosphates. Priming reactions.Priming reactions. Glycolysis begins with the addition of energy. Two high-energy phosphates from two molecules of ATP are added to the six-carbon molecule glucose, producing a six-carbon molecule with two phosphates. Energy-harvesting reactions. Finally, in a series of reactions, each of the two three-carbon sugar phosphates is converted to pyruvate. In the process, an energy-rich hydrogen is harvested as NADH, and two ATP molecules are formed.

22. Substrate-level Phosphorylation • In the last step of glycolysis, where did the P come from to make ATP? P is transferred from PEP to ADP • kinase enzyme • ADP  ATP

23. 2 ATP 2 ADP 4 ADP 4 ATP Energy accounting of glycolysis • Net gain = 2 ATP • some energy investment (2 ATP) • small energy return (4 ATP) • 1 6C sugar 2 3C sugars glucose      pyruvate 6C 3C 2x

24. Is that all there is? • Not a lot of energy… • for 1 billon years+ this is how life on Earth survived • only harvest 3.5% of energy stored in glucose • slow growth, slow reproduction

25. We can’t stop there…. • Glycolysis • Going to run out of NAD+ • How is NADH recycled to NAD+? • without regenerating NAD+, energy production would stop • another molecule must accept H from NADH glucose + 2ADP + 2Pi + 2 NAD+ 2 pyruvate + 2ATP + 2NADH NADH

26. How is NADH recycled to NAD+? • Another molecule must accept H from NADH • aerobic respiration • ethanol fermentation • lactic acid fermentation • aerobic respiration NADH

27. pyruvate  ethanol + CO2 3C 2C 1C pyruvate  lactic acid NADH NADH NAD+ NAD+ 3C 3C Anaerobic ethanol fermentation • Bacteria, yeast • beer, wine, bread • at ~12% ethanol, kills yeast • Animals, some fungi • cheese, yogurt, anaerobic exercise (no O2)

28. O2 O2 Pyruvate is a branching point Pyruvate fermentation Kreb’s cycle mitochondria

29. The Point is to Make ATP! What’s the point? ATP

30. Cellular Respiration Oxidation of Pyruvate Krebs Cycle

31. glucose      pyruvate 6C 3C 2x Glycolysis is only the start • Glycolysis • Pyruvate has more energy to yield • 3 more C to strip off (to oxidize) • if O2 is available, pyruvate enters mitochondria • enzymes of Krebs cycle complete oxidation of sugar to CO2 pyruvate       CO2 3C 1C

32. Cellular respiration

33. The Point is to Make ATP! What’s the point? ATP

34. [ ] pyruvate  acetyl CoA + CO2 2x NAD NADH 1C 3C 2C Oxidation of pyruvate • Pyruvate enters mitochondria • 3 step oxidation process • releases 1 CO2 (count the carbons!) • reduces NAD  NADH (stores energy) • produces acetyl CoA • Acetyl CoA enters Krebs cycle • where does CO2 go?

35. Pyruvate oxidized to Acetyl CoA reduction oxidation Yield = 2C sugar + CO2 + NADH

36. 1937 | 1953 Krebs cycle • aka Citric Acid Cycle • in mitochondrial matrix • 8 step pathway • each catalyzed by specific enzyme • step-wise catabolism of 6C citrate molecule • Evolved later than glycolysis • does that make evolutionary sense? • bacteria 3.5 billion years ago (glycolysis) • free O22.7 billion years ago (photosynthesis) • eukaryotes 1.5 billion years ago (aerobic respiration (organelles) Hans Krebs 1900-1981

37. 2C 6C 5C 4C 3C 4C 4C 4C 4C 6C CO2 CO2 Count the carbons! pyruvate acetyl CoA citrate x2 This happens twice for each glucose molecule oxidationof sugars

38. 2C 6C 5C 4C 3C 4C 6C 4C 4C 4C NADH CO2 CO2 NADH FADH2 NADH ATP Count the electron carriers! pyruvate acetyl CoA citrate x2 This happens twice for each glucose molecule reductionof electroncarriers

39. Whassup? So we fully oxidized glucose C6H12O6  CO2 & ended up with 4 ATP!

40. NADH & FADH2 • Krebs cycle produces large quantities of electron carriers • NADH • FADH2 • stored energy! • go to ETC

41. 4 NAD+1 FAD 4 NADH+1FADH2 1 ADP 1 ATP Energy accounting of Krebs cycle [ ] • Net gain = 2 ATP = 8 NADH + 2 FADH2 2x pyruvate          CO2 1C 3C 3x

42. So why the Krebs cycle? • If the yield is only 2 ATP, then why? • value of NADH & FADH2 • electron carriers • reduced molecules store energy! • to be used in the Electron Transport Chain

43. Cellular Respiration Electron Transport Chain

44. Cellular respiration

45. ATP accounting so far… • Glycolysis 2ATP • Kreb’s cycle 2ATP • Life takes a lot of energy to run, need to extract more energy than 4 ATP! There’s got to be a better way!

46. There is a better way! • Electron Transport Chain • series of molecules built into inner mitochondrial membrane • mostly transport proteins • transport of electrons down ETC linked to ATP synthesis • yields ~34ATP from 1 glucose! • only in presence of O2 (aerobic)

47. Mitochondria • Double membrane • outer membrane • inner membrane • highly folded cristae* • fluid-filled space between membranes = intermembranespace • matrix • central fluid-filled space * form fits function!

48. Electron Transport Chain

49. Remember the NADH? Kreb’s cycle Glycolysis PGAL 8 NADH 2 FADH2 4 NADH

50. Electron Transport Chain • NADH passes electrons to ETC • H cleaved off NADH & FADH2 • electrons stripped from H atoms  H+ (H ions) • electrons passed from one electron carrier to next in mitochondrial membrane (ETC) • transport proteins in membrane pump H+ across inner membrane to intermembrane space