Cell Respiration


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Cell Respiration

  1. 1. An Introduction To Metabolism<br />
  2. 2. Metabolism<br />The totality of an organism’s chemical processes.<br />Concerned with managing the material and energy resources of the cell.<br />
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  4. 4. Catabolic Pathways<br />Pathways that break down complex molecules into smaller ones, releasing energy.<br />Example: Respiration<br />
  5. 5. Anabolic Pathways<br />Pathways that consume energy, building complex molecules from smaller ones.<br />Example: Photosynthesis<br />
  6. 6. Energy <br />Ability to do work.<br />The ability to rearrange a collection of matter.<br />Forms of energy:<br />Kinetic<br />Potential<br />Activation<br />
  7. 7. Kinetic Energy<br />Energy of action or motion.<br />
  8. 8. Potential Energy<br />Stored energy or the capacity to do work.<br />
  9. 9. Activation Energy<br />Energy needed to convert potential energy into kinetic energy.<br />Activation Energy<br />Potential Energy<br />
  10. 10. Energy Transformation<br />Governed by the Laws of Thermodynamics.<br />
  11. 11. 1st Law of Thermodynamics<br />Energy can be transferred and transformed, but it cannot be created or destroyed.<br />Also known as the law of Conservation of Energy.<br />
  12. 12. 2nd Law of Thermodynamics<br />Each energy transfer or transformation increases the entropy of the universe.<br />
  13. 13. Entropy<br />Measure of disorder.<br />
  14. 14. Free Energy<br />The portion of a system's energy that can perform work.<br />
  15. 15. Chemical Reactions <br />Are the source of energy for living systems.<br />
  16. 16. Cell - Types of Work<br />Mechanical - muscle contractions<br />Transport - pumping across membranes<br />Chemical - making polymers<br />
  17. 17. ATP<br />Adenosine Triphosphate<br />Made of:<br /> - Adenine (nitrogenous base)<br /> - Ribose (pentose sugar)<br /> - 3 phosphate groups<br />
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  19. 19. Adenine<br />Phosphates<br />Ribose<br />
  20. 20. Key to ATP<br />Is in the three phosphate groups.<br />Negative charges repel each other and makes the phosphates unstable.<br />
  21. 21. ATP<br />Works by energizing other molecules by transferring phosphate groups.<br />
  22. 22. ATP vs Food<br />ATP: <br />Renewable energy resource.<br />Unstable bonds<br />Food:<br />Long term energy storage<br /> Stable bonds<br />
  23. 23. ATP Cycle<br />
  24. 24. ATP in Cells<br />A cell's ATP content is recycled every minute.<br />Humans use close to their body weight in ATP daily.<br />No ATP production equals quick death.<br />
  25. 25. Enzymes<br />Biological catalysts made of protein.<br />Cause the rate of a chemical reaction to increase.<br />
  26. 26. Chemical Reaction<br />AB + CD AC + BD<br />AB and CD are “reactants”<br />AC and BD are “products”<br />
  27. 27. Enzymes<br />Lower the activation energy for a chemical reaction to take place.<br />
  28. 28. Enzyme Terms<br />Substrate - the material and enzyme works on.<br />Enzyme names: Ex. Sucrase<br /> - ase name of an enzyme<br /> 1st part tells what the substrate is. (Sucrose)<br />
  29. 29. Enzyme Name<br />Some older known enzymes don't fit this naming pattern.<br />Examples: pepsin, trypsin<br />
  30. 30. Active Site<br />The area of an enzyme that binds to the substrate.<br />Structure is designed to fit the molecular shape of the substrate.<br />Therefore, each enzyme is substrate specific.<br />
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  32. 32. Enzymes <br />Usually specific to one substrate. <br />Each chemical reaction in a cell requires its own enzyme.<br />
  33. 33. Factors that Affect Enzymes<br />Environment<br />Cofactors<br />Coenzymes<br />Inhibitors<br />Allosteric Sites<br />
  34. 34. Environment<br />Factors that change protein structure will affect an enzyme.<br />Examples:<br />pH shifts<br />temperature<br />salt concentrations<br />
  35. 35. Enzyme Inhibitors<br />Competitive - mimic the substrate and bind to the active site.<br />Noncompetitive - bind to some other part of the enzyme.<br />
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  37. 37. Control of Metabolism<br />Is necessary if life is to function.<br />Controlled by switching enzyme activity "off" or "on” or separating the enzymes in time or space.<br />
  38. 38. Process of Cellular Respiration<br />
  39. 39. Process of Cellular Respiration<br />The process by which food molecules are broken down to release energy is respiration.<br />Respiration that occurs in the presence of oxygen is called aerobic respiration.<br />Respiration that occurs without oxygen is called anaerobic respiration.<br />The energy payoff is much greater when molecules are broken down aerobically.<br />
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  43. 43. Glycolysis<br />1st step of respiration<br />Glycolysis is the breakdown of glucose (6-carbon molecule to pyruvic acid (3-carbon molecule).<br />Glycolysis occurs in the cytoplasm and is anaerobic.<br />Glycolosis produces hydrogen ions and electrons, which combine with carrier ions called NAD+ (nicotanamidedinucleotide) to form NADH.<br />End product is 2 ATP’s<br />
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  46. 46. Breakdown of Pyruvic Acid<br />The 2nd step that takes place in respiration is the breakdown of pyruvic acid, and aerobic process.<br />Pyruvic acid (3-carbon molecule) is changed to acetic acid (2-carbon molecule). The carbon that comes off makes CO2. Acetic acid combines with a substance called coenzyme A (CoA), forming acetyl-CoA.<br />This process takes place in the mitochondria.<br />
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  49. 49. Citric Acid Cycle<br />The 3rd step of aerobic respiration is the citric acid cycle.<br />Acetyl-CoA combines with a 4-carbon molecule to form a 6-carbon molecule, citric acid. Citric acid is broken down 1st to a 5-carbon molecule and then to a 4-carbon molecule, releasing CO2 at each step.<br />This cycle of chemical reactions produces more ATP and releases additional electrons.<br />
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  53. 53. Electron Transport Chain<br />The 4th part of aerobic respiration is the electron transport chain (ETC).<br />The ETC is a series of molecules along which electrons are transferred, releasing energy.<br />Carrier molecules bring the electrons released during glycolysis and the citric acid cycle to the ETC.<br />
  54. 54. ETC (con’t)<br />The molecules of the ETC are located on the inner membranes of the mitochondria.<br />This is an aerobic process, because oxygen combines with two hydrogen ions to produce with water.<br />
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  59. 59. What happens if no oxygen is present?<br />If the final electron acceptor, oxygen, is used up, the chain becomes jammed. The reactions of the ETC can’t take place without oxygen.<br />
  60. 60. Anaerobic Respiration<br />
  61. 61. Anaerobic Respiration <br />If oxygen isn’t present, there’s no electron acceptor to accept the electrons at the end of the ETC.<br />If this occurs, then NADH accumulates.<br />Once all the NAD+ has been converted to NADH, the Krebs cycle and glycolysis both stop (both need NAD+ to accept electrons).<br />
  62. 62. Once this happens, no new ATP is produced, and the cell soon dies. Cells have derived a method to escape dying – ANAEROBIC RESPIRATION.<br />The main objective of anaerobic respiration is to replenish NAD+ so that glycolysis can proceed once again. It occurs in the cytoplasm right along with glycolysis.<br />
  63. 63. There are two forms of anaerobic respiration:<br />Alcoholic fermentation<br />Lactic acid fermentation<br />
  64. 64. Alcoholic Fermentation<br />Alcoholic fermentation occurs in plants, fungi (yeast), and bacteria.<br />There are 2 steps to alcoholic fermentation:<br />The conversion of pyruvic acid to acetaldehyde<br />1 CO2 and 1 acetaldehyde is produced<br />The conversion of acetaldehyde to ethanol<br />NADH is used to drive the reaction, releasing NAD+<br />
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  66. 66. The goal of this reaction is not to produce ethanol, but it is to free the NAD+, which allows glycolysis to continue.<br />The reward is 2 ATP from glycolysis for each 2 converted pyruvate. This is better than the alternative, which is 0 ATP.<br />
  67. 67. Lactic Acid Fermentation<br />Lactic acid can occur in some bacteria and plants, but it is mostly found in animals, including humans.<br />Anytime your muscle cells require energy at a faster rate than it can be supplied by aerobic respiration, they begin to carry out lactic acid fermentation.<br />
  68. 68. There is only one step in lactic acid fermentation:<br />Now, NAD+ can be used for glycolysis.<br />When O2 becomes available again, lactic acid can be broken down and its store of energy can be retrieved.<br />Because O2 is required to do this, lactic acid fermentation creates what is often called an oxygen debt.<br />
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  70. 70. Lactic Acid Fermentation<br />Uses only Glycolysis.<br />An incomplete oxidation - energy is still left in the products (lactic acid). <br />Does NOT require O2<br />Produces ATP when O2 is not available.<br />
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  72. 72. Lactic Acid Fermentation<br />Done by human muscle cells under oxygen debt.<br />Lactic Acid is a toxin and causes soreness and stiffness in muscles.<br />
  73. 73. Fermentation - Summary<br />Way of using up NADH so Glycolysis can still run.<br />Provides ATP to a cell even when O2 is absent.<br />
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  75. 75. Aerobic vs Anaerobic<br />Aerobic - Rs with O2<br />Anaerobic - Rs without O2<br />Aerobic - All three Rs steps.<br />Anaerobic - Glycolysis only.<br />