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Chapter 10 Metabolism


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Chapter 10 Metabolism

  1. 1. Plant Metabolism
  2. 2. Outline <ul><li>Photosynthesis </li></ul><ul><ul><li>Major Steps of Photosynthesis </li></ul></ul><ul><ul><li>Light-Dependent Reactions </li></ul></ul><ul><ul><li>Light-Independent Reactions </li></ul></ul><ul><ul><li>C 4 Photosynthesis </li></ul></ul><ul><ul><li>CAM Photosynthesis </li></ul></ul><ul><li>Respiration </li></ul><ul><ul><li>Glycolysis </li></ul></ul><ul><ul><li>Electron Transport Chain </li></ul></ul>
  3. 3. Enzymes and Energy Transfer <ul><li>Enzymes regulate most metabolic activities. </li></ul><ul><ul><li>Anabolism - Storing Energy </li></ul></ul><ul><ul><ul><li>Photosynthesis reactions </li></ul></ul></ul><ul><ul><li>Catabolism - Consuming Stored Energy </li></ul></ul><ul><ul><ul><li>Respiration reactions </li></ul></ul></ul><ul><li>Oxidation-Reduction Reactions </li></ul><ul><ul><li>Oxidation - Loss of electron(s) </li></ul></ul><ul><ul><li>Reduction - Gain of electron(s) </li></ul></ul>
  4. 5. Photosynthesis <ul><li>Energy for most cellular activity involves adenosine triphosphate ( ATP ). </li></ul><ul><ul><li>Plants make ATP using light as an energy source. </li></ul></ul><ul><ul><ul><li>Takes place in cholorpolasts and other green parts of the organisms. </li></ul></ul></ul><ul><li>6CO 2 +12H 2 O + light  C 6 H 12 O 6 +6O 2 +6H 2 O </li></ul>
  5. 6. Water <ul><li>Less than 1% of all the water absorbed by plants is used in photosynthesis. </li></ul><ul><ul><li>Most of the remainder is transpired or incorporated into plant materials. </li></ul></ul><ul><li>If water is in short supply, stomata usually close, reducing the supply of carbon dioxide available for photosynthesis. </li></ul>
  6. 7. Light <ul><li>About 40% of the radiant energy received on earth is in the form of visible light. </li></ul><ul><ul><li>Leaves commonly absorb about 80% of the visible light reaching them. </li></ul></ul><ul><ul><ul><li>Light intensity varies with time of day, season, altitude, latitude, and atmospheric composition. </li></ul></ul></ul><ul><ul><ul><ul><li>Considerable variation in the light intensities necessary for optimal photosynthetic rates. </li></ul></ul></ul></ul>
  7. 8. Light Wavelengths
  8. 9. Effects of Light and Temperature on Photosynthesis
  9. 10. Chlorophyll <ul><li>Several different types of chlorophyll. </li></ul><ul><ul><li>Most plants contain both chlorophyll a (blue-green) and chlorophyll b (yellow-green). </li></ul></ul><ul><ul><ul><li>Other pigments include carotenoids (yellow and orange) phycobilins (blue or red), and other types of chlorophyll. </li></ul></ul></ul><ul><ul><ul><li>About 250-400 pigment molecules group as a photosynthetic unit . </li></ul></ul></ul>
  10. 11. Major Steps of Photosynthesis <ul><li>Light Dependent Reactions </li></ul><ul><ul><li>Water molecules split apart </li></ul></ul><ul><ul><li>Electrons passed along electron transport </li></ul></ul><ul><ul><li>ATP produced </li></ul></ul><ul><ul><li>NADPH produced </li></ul></ul>
  11. 12. Major Steps of Photosynthesis <ul><li>Light Independent Reactions </li></ul><ul><ul><li>Calvin Cycle (carbon-fixing reactions) </li></ul></ul><ul><ul><ul><li>Carbon dioxide combined with RuBP and then combined molecules are converted to sugars (Glucose). </li></ul></ul></ul><ul><ul><ul><ul><li>Energy furnished by ATP and NADPH from Light-Dependent Reactions. </li></ul></ul></ul></ul>
  12. 13. Light Dependent Reactions - In Depth <ul><li>Each pigment has its own distinctive pattern of light absorption. </li></ul>
  13. 14. Light Dependent Reactions - In Depth <ul><li>Two types of photosynthetic units present in most chloroplasts make up photosystems . </li></ul><ul><ul><li>Photosystems I and II </li></ul></ul><ul><ul><ul><li>Both can produce ATP. </li></ul></ul></ul><ul><ul><ul><li>Only organisms with both photosystem I and photosystem II can produce NADPH and oxygen as a consequence of electron flow. </li></ul></ul></ul>
  14. 16. Photosystems
  15. 17. Light Independent Reactions - In Depth <ul><li>Calvin Cycle </li></ul><ul><ul><li>Six molecules of CO 2 combine with six molecules of RuBP with the aid of rubisco. </li></ul></ul><ul><ul><li>Resulting complexes split into twelve 3PGA molecules. </li></ul></ul><ul><ul><li>NADPH and ATP supply energy and electrons that reduce 3PGA to 12 GA3P. </li></ul></ul><ul><ul><li>Ten of the twelve GA3P molecules are restructured into six RuBP molecules. </li></ul></ul>
  16. 18. The Calvin Cycle
  17. 19. Photorespiration <ul><li>Stomata usually close on hot, dry days. </li></ul><ul><ul><li>Closed stomata prevent carbon dioxide from entering the leaf. </li></ul></ul><ul><ul><ul><li>When carbon dioxide levels drop below about 50 parts per million, photorespiration is initiated. </li></ul></ul></ul><ul><ul><ul><ul><li>Rubisco fixes oxygen instead of carbon dioxide. </li></ul></ul></ul></ul>
  18. 20. Light Independent Reactions - In Depth <ul><li>4-Carbon Pathway </li></ul><ul><ul><li>Plants have Kranz Anatomy . </li></ul></ul><ul><ul><ul><li>Large chloroplast with few to no grana in the bundle sheath cells surrounding the veins. </li></ul></ul></ul><ul><ul><ul><li>Smaller chloroplasts with well-developed grana in the mesophyll cells. </li></ul></ul></ul>
  19. 21. Corn (Zea Mays) Cross-Section
  20. 22. 4-Carbon Pathway <ul><li>Plants with Kranz Anatomy produce oxaloacetic acid (4-carbon compound). </li></ul><ul><ul><li>Phosphoenolpyruvate ( PEP ) and carbon dioxide combined in mesophyll cells with the aid of PEP carboxylase. </li></ul></ul><ul><ul><ul><li>Provides a major reduction in photorespiration. </li></ul></ul></ul>
  21. 23. CAM Photosynthesis <ul><li>Similar to C4 photosynthesis in that 4-carbon compounds are produced during the light-independent reactions. </li></ul><ul><ul><li>However, in CAM, the organic acids accumulate at night and break down during the day, releasing carbon dioxide. </li></ul></ul><ul><ul><ul><li>Allows plants to function well under limited water supplies, as well as high light intensity. </li></ul></ul></ul>
  22. 24. CAM Photosynthesis
  23. 25. Respiration <ul><li>Respiration is essentially the release of energy from glucose molecules that are broken down to individual carbon dioxide molecules. </li></ul><ul><li>C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + energy </li></ul>
  24. 26. Respiration <ul><li>Fermentation </li></ul><ul><li>C 6 H 12 O 6  2C 2 H 5 OH + 2CO 2 + ATP </li></ul><ul><li>C 6 H 12 O 6  2C 3 H 6 O 3 + ATP </li></ul>
  25. 27. Major Steps of Respiration <ul><li>Glycolysis </li></ul><ul><ul><li>Glucose molecule becomes a fructose molecule carrying two phosphates. </li></ul></ul><ul><ul><li>Fructose molecule is split into two GA3P molecules. </li></ul></ul><ul><ul><li>Phosphates and hydrogens are removed </li></ul></ul><ul><ul><ul><li>Creating a net gain of 2 ATP and 2 NADH molecules from one glucose molecule </li></ul></ul></ul>
  26. 28. Major Steps of Respiration <ul><li>Aerobic Respiration </li></ul><ul><ul><li>Citric Acid (Krebs) Cycle </li></ul></ul><ul><ul><ul><li>1 ATP, 3 NADH, 1 FADH 2 </li></ul></ul></ul><ul><li>Electron Transport </li></ul><ul><ul><li>Oxidative Phosphorylation </li></ul></ul><ul><ul><ul><li>Energy contained in 1 NADH molecule is used to create 3 ATP molecules </li></ul></ul></ul><ul><ul><ul><li>Energy contained in 1 FADH 2 molecule is used to create 2 ATP molecules </li></ul></ul></ul><ul><li>Total number of ATPs produced = 36 </li></ul>
  27. 30. Assimilation and Digestion <ul><li>Assimilation - the process of using organic matter produced through photosynthesis to build protoplasm and cell walls </li></ul><ul><li>Digestion - the conversion of starch and other insoluble carbohydrates to soluble forms </li></ul><ul><ul><li>Nearly always hydrolysis </li></ul></ul>