Kr ebs cycle and anaerobic respiration


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  • Please don't equate fermentation with anaerobic respiration. Anaerobic respiration is a microbial process using alternate terminal electron acceptors other than oxygen. Bacteria use anaerobic respiration for oxidative phosphorylation; they just can't get as much ATP as with aerobic respiration.
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Kr ebs cycle and anaerobic respiration

  1. 1. Krebs Cycle (Citric Acid Cycle)& Quick and Long Energy<br />
  2. 2. Glycolysis<br />Glucose<br />2 molecules of pyruvate<br />To the electron transport chain<br />
  3. 3. Energy accounting of glycolysis <br />2 ATP<br />2 ADP<br />4 ADP<br />2 NAD+<br />ATP<br />4<br />2<br />glucose      pyruvate<br />6C<br />3C<br />2x<br />All that work! And that’s all I get?<br />Butglucose hasso much moreto give!<br />Net gain = 2 ATP + 2 NADH<br />some energy investment (-2 ATP)<br />small energy return (4 ATP + 2 NADH)<br />1 6C sugar 2 3C sugars<br />
  4. 4. Krebs Cycle<br />British biochemist Hans Krebs, discovered 1937<br />During Krebs cycle, PYRUVATE is broken down into CARBON DIOXIDE in a series of energy extracting reactions<br />AKA the CITRIC ACID CYCLE because citrate (also called citric acid) is the first product of the cycle<br />
  5. 5. From Glycolysis comes the Pyruvates….<br />
  6. 6. Krebs Cycle<br />
  7. 7. Step 1<br />Citric Acid Production<br />Pyruvate ( 3-carbons) enter mitochondria Matrix<br />One carbon is removed as CO2 (WASTE product) and electrons are removed by NAD+ (making NADH which goes to the ETC)<br />Co-enzyme A joins the 2-carbon molecule (that used to be pyruvate) making Acetyl-CoA<br />Now Acetyl-CoA can enter the Krebs cycle<br />Acetyl Co-A combines with 4-carbon molecule called OXALOACETATE , making citrate (citric acid), a 6-carbon molecule<br />
  8. 8. Step 2<br />Citric acid (6 carbon molecule) is broken down into a few different 5-carbon compounds, then into a few different 4-carbon compounds.<br />Each step releases CO2, NADH and FADH2, and ATP<br />CO2 is a waste product (breath out!)<br />NADH and FADH2 (taxi cabs) goes onto the ETC (where the party is at)<br />ATP is used for cell to do work (mechanical, chemical, or transport)<br />
  9. 9. 2C<br />6C<br />5C<br />4C<br />3C<br />4C<br />6C<br />4C<br />4C<br />4C<br />CO2<br />CO2<br />Count the carbons!<br />acetyl CoA<br />pyruvate<br />citrate<br />oxidationof sugars<br />This happens twice for each glucose molecule<br />x2<br />
  10. 10. 2C<br />6C<br />5C<br />4C<br />3C<br />4C<br />6C<br />4C<br />4C<br />4C<br />NADH<br />ATP<br />CO2<br />CO2<br />CO2<br />NADH<br />NADH<br />FADH2<br />NADH<br />Count the electron carriers!<br />acetyl CoA<br />pyruvate<br />citrate<br />reductionof electroncarriers<br />This happens twice for each glucose molecule<br />x2<br />
  11. 11. Whassup?<br />So we fully oxidized (broke down) glucose <br />C6H12O6<br /><br />CO2<br />& ended up with 4 ATP!<br />What’s the point? <br />
  12. 12. H+<br />H+<br />H+<br />H+<br />H+<br />H+<br />H+<br />H+<br />H+<br />Electron Carriers = Hydrogen Carriers<br /><ul><li>Krebs cycle produces large quantities of electron carriers
  13. 13. NADH
  14. 14. FADH2
  15. 15. go to Electron Transport Chain!</li></ul>ADP+ Pi<br />ATP<br />What’s so important about electron carriers? <br />
  16. 16. 4 NAD+1 FAD<br />4 NADH+1FADH2<br />2x<br />1C<br />3x<br />1 ADP<br />1 ATP<br />Energy accounting of Krebs cycle <br />pyruvate          CO2<br />3C<br />ATP<br />Net gain = 2 ATP<br />= 8 NADH + 2 FADH2<br />
  17. 17. Value of Krebs cycle?<br />If the yield is only 2 ATP then how was the Krebs cycle an adaptation?<br />value of NADH & FADH2<br />electron carriers & H carriers<br />to be used in the Electron Transport Chain<br />like $$in the bank<br />
  18. 18.
  19. 19. Summary<br />In one turn of the Krebs Cycle:<br />3 CO2 (1 from right before Krebs)<br />Released when we exhale<br />1 ATP (E for cell work)<br />1 NADH from right before Krebs<br />3 NADH from Krebs (to ETC)<br />1 FADH2 (to ETC)<br />Water leaves and then reenters so we don’t count it in the products<br />For one Glucose molecule how many times does the Krebs Cycle turn?<br />What are the totals from the Krebs Cycle for one Glucose molecule?<br />6 CO2s<br />2 ATPs<br />8 NADHS<br />2 FADH2<br />
  20. 20. So we use Krebs if we have oxygen….what if there is NO oxygen???<br />Then we can’t even enter the mitochondria and go to the Krebs cycle…<br />We are stuck using Glycolysis…<br />Anaerobic respiration (NO oxygen)<br />2 types<br />Lactic acid fermentation<br />Alcohol fermentation<br />
  21. 21. Pyruvate is a branching point<br />O2<br />O2<br />Pyruvate<br />fermentation<br />anaerobicrespiration<br />mitochondria<br />Krebs cycle<br />aerobic respiration<br />
  22. 22. Glycolysis<br />???<br />Pyruvate<br />or<br />2<br />
  23. 23. Cells cannot get enough oxygen<br />Build up of pyruvic acid and NADH and no oxygen to break it down<br />Cells begin fermentation<br />Lactic Acid fermentation<br />Pyruvic acid + NADH lactic acid + NAD+<br />Get about 90 seconds of energy without having to use oxygen<br />HOWEVER, oxygen will be paid back double when you are done (think heavy breathing)<br />Occurs in muscle cells, and microorganisms, such as the ones that turn milk into cheese and yogurt<br />Lactic acid causes muscle cramping and burning sensation<br />Oxygen is required to break down lactic acid and get it out of body<br />Alcohol fermentation<br />Pyruvic acid + NADH ethyl alcohol + NAD+ + CO2<br />Occurs in yeast cells and other microorganisms, such as the ones involved in the production of bread and wine<br />
  24. 24. recycleNADH<br />How is NADH recycled to NAD+?<br />without oxygen<br />anaerobic respiration<br />“fermentation”<br />with oxygen<br />aerobic respiration<br />Another molecule must accept H from NADH<br />pyruvate<br />NAD+<br />H2O<br />CO2<br />NADH<br />NADH<br />O2<br />acetaldehyde<br />NADH<br />acetyl-CoA<br />NAD+<br />NAD+<br />lactate<br />lactic acidfermentation<br />which path you use depends on who you are…<br />Krebs<br />cycle<br />ethanol<br />alcoholfermentation<br />
  25. 25. Fermentation (anaerobic)<br />pyruvate  ethanol + CO2<br />1C<br />3C<br />2C<br />pyruvate  lactic acid<br />NADH<br />NAD+<br />NADH<br />NAD+<br />3C<br />3C<br />Bacteria, yeast<br />back to glycolysis<br /><ul><li>beer, wine, bread
  26. 26. Animals, some fungi</li></ul>back to glycolysis<br /><ul><li>cheese, anaerobic exercise (no O2)</li></li></ul><li>Alcohol Fermentation<br />pyruvate  ethanol + CO2<br />1C<br />3C<br />2C<br />NADH<br />NAD+<br />recycleNADH<br />bacteria yeast<br />back to glycolysis<br /><ul><li>Dead end process
  27. 27. at ~12% ethanol, kills yeast
  28. 28. can’t reverse the reaction</li></ul>Count thecarbons!<br />
  29. 29. Lactic Acid Fermentation<br />O2<br />pyruvate  lactic acid<br />NADH<br />NAD+<br />3C<br />3C<br />recycleNADH<br />animalssome fungi<br /><br />back to glycolysis<br /><ul><li>Reversible process
  30. 30. once O2 is available, lactate is converted back to pyruvate by the liver</li></ul>Count thecarbons!<br />
  31. 31. Quick Energy<br />3 ways to obtain energy<br />ATP stored in muscles (glycogen) (short)<br />ATP from lactic acid (short)<br />ATP from cellular respiration (long)<br />Cells initially have small amount of ATP from cell resp. and glycolysis<br />Think of running a 200 m sprint<br />Gun goes off<br />Muscles of runner contract, turning glycogen in muscle cells into glucose, but this only provides for a few seconds of intense activity<br />You pass the 50m mark<br />most ATP the was initially stored is now gone<br />Muscle cells are producing ATP from lactic acid fermentation<br />This lasts about 90 seconds<br />End of Race<br />Lots of lactic acid build up<br />Only way to get rid of lactic acid is a chemical pathway that requires oxygen<br />Thus, at the end of the race, you are breathing heavily and you should follow an intense work out with a slow jog<br />
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  33. 33.
  34. 34. Long Term<br />Energy for running long races or other endurance sports<br />Cellular respiration is the only way to get enough ATP to last the length of the race<br />Cellular respiration makes ATP more slowly than lactic acid fermentation<br />Athletes must pace themselves<br />Glycogen an important molecule<br />Carbohydrate<br />Polysaccharide (monosaccharide is glucose)<br />Muscle and liver cells store E as glycogen<br />Glycogen is broken down by the hormone Glucagon<br />Glycogen break down is also stimulated by muscle contraction<br />When you work out, muscles contract and they can use energy stored in glycogen<br />Increase glycogen storage, increase the duration of exhaustive work your muscles can do<br />Stores of glycogen last about 15-20 minutes <br />After glycogen is used up, body starts to break down other molecules to get energy<br />Fats and proteins<br />Fatty acids are broken down and carried to mitochondrial matrix and enter the membrane in fragments as acetyl-CoA<br />Proteins are broken down into aa and the these modified aa’s are fed back into the Krebs cycle (NAD+ and FAD)<br />Aerobic exercise is good for weight control because it leads to break down of fats<br />
  35. 35. Training to Improve Function of ATP production<br />Anaerobic training<br />Increase levels of glycogen in muscle cells and increase tolerance of lactic acid build up<br />Aerobic training<br />Increases size and number of mitochondria in muscle cells and increase delivery of oxygen to muscle cells by improving heart and lung efficiency<br />
  36. 36. 2007-2008<br />What’s thepoint?<br />The pointis to makeATP!<br />ATP<br />