1. Krebs Cycle (Citric Acid Cycle)& Quick and Long Energy

2. Glycolysis Glucose 2 molecules of pyruvate To the electron transport chain

3. Energy accounting of glycolysis 2 ATP 2 ADP 4 ADP 2 NAD+ ATP 4 2 glucose      pyruvate 6C 3C 2x All that work! And that’s all I get? Butglucose hasso much moreto give! Net gain = 2 ATP + 2 NADH some energy investment (-2 ATP) small energy return (4 ATP + 2 NADH) 1 6C sugar 2 3C sugars

4. Krebs Cycle British biochemist Hans Krebs, discovered 1937 During Krebs cycle, PYRUVATE is broken down into CARBON DIOXIDE in a series of energy extracting reactions AKA the CITRIC ACID CYCLE because citrate (also called citric acid) is the first product of the cycle

5. From Glycolysis comes the Pyruvates….

6. Krebs Cycle

7. Step 1 Citric Acid Production Pyruvate ( 3-carbons) enter mitochondria Matrix One carbon is removed as CO2 (WASTE product) and electrons are removed by NAD+ (making NADH which goes to the ETC) Co-enzyme A joins the 2-carbon molecule (that used to be pyruvate) making Acetyl-CoA Now Acetyl-CoA can enter the Krebs cycle Acetyl Co-A combines with 4-carbon molecule called OXALOACETATE , making citrate (citric acid), a 6-carbon molecule

8. Step 2 Citric acid (6 carbon molecule) is broken down into a few different 5-carbon compounds, then into a few different 4-carbon compounds. Each step releases CO2, NADH and FADH2, and ATP CO2 is a waste product (breath out!) NADH and FADH2 (taxi cabs) goes onto the ETC (where the party is at) ATP is used for cell to do work (mechanical, chemical, or transport)

9. 2C 6C 5C 4C 3C 4C 6C 4C 4C 4C CO2 CO2 Count the carbons! acetyl CoA pyruvate citrate oxidationof sugars This happens twice for each glucose molecule x2

10. 2C 6C 5C 4C 3C 4C 6C 4C 4C 4C NADH ATP CO2 CO2 CO2 NADH NADH FADH2 NADH Count the electron carriers! acetyl CoA pyruvate citrate reductionof electroncarriers This happens twice for each glucose molecule x2

11. Whassup? So we fully oxidized (broke down) glucose C6H12O6  CO2 & ended up with 4 ATP! What’s the point?

13. NADH

14. FADH2

15. go to Electron Transport Chain!ADP+ Pi ATP What’s so important about electron carriers?

16. 4 NAD+1 FAD 4 NADH+1FADH2 2x 1C 3x 1 ADP 1 ATP Energy accounting of Krebs cycle pyruvate          CO2 3C ATP Net gain = 2 ATP = 8 NADH + 2 FADH2

17. Value of Krebs cycle? If the yield is only 2 ATP then how was the Krebs cycle an adaptation? value of NADH & FADH2 electron carriers & H carriers to be used in the Electron Transport Chain like $$in the bank

19. Summary In one turn of the Krebs Cycle: 3 CO2 (1 from right before Krebs) Released when we exhale 1 ATP (E for cell work) 1 NADH from right before Krebs 3 NADH from Krebs (to ETC) 1 FADH2 (to ETC) Water leaves and then reenters so we don’t count it in the products For one Glucose molecule how many times does the Krebs Cycle turn? What are the totals from the Krebs Cycle for one Glucose molecule? 6 CO2s 2 ATPs 8 NADHS 2 FADH2

20. So we use Krebs if we have oxygen….what if there is NO oxygen??? Then we can’t even enter the mitochondria and go to the Krebs cycle… We are stuck using Glycolysis… Anaerobic respiration (NO oxygen) 2 types Lactic acid fermentation Alcohol fermentation

21. Pyruvate is a branching point O2 O2 Pyruvate fermentation anaerobicrespiration mitochondria Krebs cycle aerobic respiration

22. Glycolysis ??? Pyruvate or 2

23. Cells cannot get enough oxygen Build up of pyruvic acid and NADH and no oxygen to break it down Cells begin fermentation Lactic Acid fermentation Pyruvic acid + NADH lactic acid + NAD+ Get about 90 seconds of energy without having to use oxygen HOWEVER, oxygen will be paid back double when you are done (think heavy breathing) Occurs in muscle cells, and microorganisms, such as the ones that turn milk into cheese and yogurt Lactic acid causes muscle cramping and burning sensation Oxygen is required to break down lactic acid and get it out of body Alcohol fermentation Pyruvic acid + NADH ethyl alcohol + NAD+ + CO2 Occurs in yeast cells and other microorganisms, such as the ones involved in the production of bread and wine

24. recycleNADH How is NADH recycled to NAD+? without oxygen anaerobic respiration “fermentation” with oxygen aerobic respiration Another molecule must accept H from NADH pyruvate NAD+ H2O CO2 NADH NADH O2 acetaldehyde NADH acetyl-CoA NAD+ NAD+ lactate lactic acidfermentation which path you use depends on who you are… Krebs cycle ethanol alcoholfermentation

27. at ~12% ethanol, kills yeast

28. can’t reverse the reactionCount thecarbons!

30. once O2 is available, lactate is converted back to pyruvate by the liverCount thecarbons!

31. Quick Energy 3 ways to obtain energy ATP stored in muscles (glycogen) (short) ATP from lactic acid (short) ATP from cellular respiration (long) Cells initially have small amount of ATP from cell resp. and glycolysis Think of running a 200 m sprint Gun goes off Muscles of runner contract, turning glycogen in muscle cells into glucose, but this only provides for a few seconds of intense activity You pass the 50m mark most ATP the was initially stored is now gone Muscle cells are producing ATP from lactic acid fermentation This lasts about 90 seconds End of Race Lots of lactic acid build up Only way to get rid of lactic acid is a chemical pathway that requires oxygen Thus, at the end of the race, you are breathing heavily and you should follow an intense work out with a slow jog

34. Long Term Energy for running long races or other endurance sports Cellular respiration is the only way to get enough ATP to last the length of the race Cellular respiration makes ATP more slowly than lactic acid fermentation Athletes must pace themselves Glycogen an important molecule Carbohydrate Polysaccharide (monosaccharide is glucose) Muscle and liver cells store E as glycogen Glycogen is broken down by the hormone Glucagon Glycogen break down is also stimulated by muscle contraction When you work out, muscles contract and they can use energy stored in glycogen Increase glycogen storage, increase the duration of exhaustive work your muscles can do Stores of glycogen last about 15-20 minutes After glycogen is used up, body starts to break down other molecules to get energy Fats and proteins Fatty acids are broken down and carried to mitochondrial matrix and enter the membrane in fragments as acetyl-CoA Proteins are broken down into aa and the these modified aa’s are fed back into the Krebs cycle (NAD+ and FAD) Aerobic exercise is good for weight control because it leads to break down of fats

35. Training to Improve Function of ATP production Anaerobic training Increase levels of glycogen in muscle cells and increase tolerance of lactic acid build up Aerobic training Increases size and number of mitochondria in muscle cells and increase delivery of oxygen to muscle cells by improving heart and lung efficiency

36. 2007-2008 What’s thepoint? The pointis to makeATP! ATP