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  1. CELLULAR RESPIRATION Cellular Respiration – Chapter 9

  2. Cellular Respiration Equation: C6H12O6 + 6O2 6CO2 +6H2O + energy Cellular Respiration – Chapter 9

  3. Cell Respiration – is a complex process in which cells make ATP by breaking down organic compounds • The break down of organic compounds releases energy; some is used to make ATP. Cellular Respiration – Chapter 9

  4. Cellular Respiration – Chapter 9

  5. Glycolysis and Fermentation: Cell respiration begins with a biochemical pathway called glycolysis. Glycolysis makes little ATP. The products of glycolysis can then follow one of two pathways. Each pathways depends on whether there is oxygen or not. Cellular Respiration – Chapter 9

  6. Organic Compounds Glycolysis Fermentation (Anaerobic) Aerobic Respiration Oxygen Absent Oxygen Present ATP Cellular Respiration – Chapter 9

  7. Glycolysis • A pathway in which glucose a 6-carbon compound is oxidized to produce two 3-Carbon molecules of pyruvic acid. (All reactions of glycolysis occur in the cytosol of the cell.) Cellular Respiration – Chapter 9

  8. Oxidized– a reaction where a reactant loses one or more electrons, and becomes more positive Cellular Respiration – Chapter 9

  9. There are 4 steps to Glycolysis: • Two phosphates are added to glucose and it becomes a new 6-carbon compound • The 6-carbon compound splits into two 3-carbon PGAL’s • The two PGAL’s are oxidized and each gains a phosphate. At the same time 2 NAD molecules each gain a Hydrogen molecule. • The phosphates from step 1 and 3 are removed and the compound pyruvic acid is made. The 4 phosphates attach to ADP molecules and 4 molecules of ATP are made. Cellular Respiration – Chapter 9

  10. Two ATP molecules are used in gylcolysis and 4 molecules of ATP are made therefore there is a net yield of 2 ATP molecules for every molecule of glucose that is converted to pyruvic acid. Cellular Respiration – Chapter 9

  11. Cellular Respiration – Chapter 9

  12. Fermentation: • Conversion in absence of oxygen of pyruvic acid into other compounds • Happens in the cell’s cytosol Cellular Respiration – Chapter 9

  13. Lactic Acid Fermentation • Enzyme converts pyruvic acid into another 3-carbon compound, called lactic acid • 2 hydrogen (H) atoms from NADH and H add to pyruvic acid to make the final product of lactic acid Cellular Respiration – Chapter 9

  14. Examples of Lactic Acid: Plays a role in food production • Yogurt and cheese made because of the fermentation of microorganismsOccurs in muscle cells • Strenuous exercise – muscles use the oxygen faster than it’s delivered. Muscles turn to lactic acid fermentation, cells build up with the acid • Results in muscle fatigue, pain, and cramps Cellular Respiration – Chapter 9

  15. Alcoholic Fermentation • Converts pyruvic acid into ethyl alcohol • Carbon dioxide is removed from pyruvic acid leaving a 2-carbon compound. • Hydrogen atoms are added to the 2-carbon compound resulting in ethyl alcohol. Cellular Respiration – Chapter 9

  16. Examples of Alcoholic Fermentation: • Wine and beer • Yeast cells are added to the fermentation mixture to produce the enzymes needed for alcoholic fermentation • Ethyl alcohol increases to the point where fermentation stops • Carbon dioxide accumulates, creates “carbonate” of the beverage • Bread • Ethyl alcohol evaporates in baking but carbon dioxide created the bubbles in the dough Cellular Respiration – Chapter 9

  17. Energy Yield of Glycolysis: • Efficiency of glycolysis =Energy required to make ATP /Energy released by oxidation of glucose • Glycolysis is only 3.5% efficient. • Most of the energy that was contained in the glucose is still contained the pyruvic acid. Cellular Respiration – Chapter 9

  18. HISTORY • Anaerobic organisms evolved very early in the history of life on earth. • Oxygen was not produced until photosynthetic organisms came along about a billion years later • Most anaerobic organisms are unicellular, any anaerobic multicellular organisms are very small Cellular Respiration – Chapter 9

  19. Aerobic Respiration: • In most cells the pyruvic acid made in glycolysis does not go into fermentation but instead if oxygen is available the pyruvic acid enters cellular respiration. • There are 2 major steps to Aerobic or Cellular Respiration: • Krebs Cycle • Electron Transport Chain Cellular Respiration – Chapter 9

  20. Where the reactions for Kreb’s cycle and Electron Transport take place: • Prokaryotes – in the cytosol of the cell • Eukaryotes – inside the mitochondria • When the pyruvic acid enters the mitochondria it combines with a molecule called coenzyme A to form acetyl coenzyme A. (Abbreviated acetyl coA) Cellular Respiration – Chapter 9

  21. The Kreb’s Cycle: • Is a biochemical pathway that breaks down acetyl CoA, producing CO2, hydrogen atoms, and ATP. • The person who identified the reactions that make up the cycle was Hans Krebs a German-British biochemist. Cellular Respiration – Chapter 9

  22. The Krebs Cycle has 5 main steps: • Acetyl CoA combines with oxaloacetic acid to produce citric acid • Citric acid releases a Carbon dioxide molecule to form a five-carbon compound • The five-carbon compound releases a carbon dioxide molecule to form a four-carbon compound • The four-carbon compound is converted into a new four-carbon compound • The new four-carbon compound is converted back into oxaloacetic acid Cellular Respiration – Chapter 9

  23. Krebs Cycle Continued • In addition to the carbon dioxide produced, each turn of the Kreb’s cycle produces ATP, NADH, and FADH2 • Each glucose molecule makes 2 pyruvic acid molecules in glycolysis. The 2 pyruvic acid molecules then make 2 acetyl CoA molecules (Each will go through the Kreb’s Cycle.) Cellular Respiration – Chapter 9

  24. From the two acetyl CoA molecules in the Kreb’s Cycle these are produced (2 turns of the Kreb’s Cycle): • 6 NADH • 2 FADH2 • 4 CO2 • 2 ATP Cellular Respiration – Chapter 9

  25. Cellular Respiration – Chapter 9

  26. Electron Transport Chain: • The second stage of aerobic or cellular respiration • Electron transport chain lines the inner membrane of the mitochondria Cellular Respiration – Chapter 9

  27. What happens in the Electron Transport Chain: • NADH and FADH2 supply electrons and protons to the electron transport chain • The electrons move down the chain from molecules to molecule in a series of reactions • The protons are pumped outside the mitochondria Cellular Respiration – Chapter 9

  28. Electron Transport Chain Cont. • As the protons return to the mitochondria matrix through ATP synthase, they release energy, that energy is used to make ATP • The electrons and protons are joined with oxygen this reaction makes ATP Cellular Respiration – Chapter 9

  29. Energy Yield for Aerobic Respiration: • Efficiency of Aerobic Respiration = Energy used to make ATP Energy released by oxidation of glucose • Aerobic Respiration is 66% efficient (20 x more than glycolysis) • 1 molecule of glucose can produce up to 38 ATP in cellular respiration (see diagram) usually 36 ATP net yeild Cellular Respiration – Chapter 9

  30. Cellular Respiration – Chapter 9

  31. Cellular Respiration – Chapter 9

  32. Cellular Respiration – Chapter 9

  33. Cellular Respiration – Chapter 9