Ap Bio Ch6 PowerPoint


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Energy Flow in the Life of a Cell

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Ap Bio Ch6 PowerPoint

  1. 1. Energy Flow in Cells
  2. 2. The Laws of Thermodynamics <ul><li>First Law of Thermodynamics </li></ul><ul><ul><li>Energy can neither be created nor destroyed </li></ul></ul><ul><ul><li>The total amount of energy within a given system remains constant unless energy is added or removed from the system </li></ul></ul><ul><li>The Second Law of Thermodynamics </li></ul><ul><ul><li>The amount of useful energy decreases when energy is converted from one form to another </li></ul></ul><ul><ul><li>Entropy (disorder) increases </li></ul></ul>
  3. 4. Energy of Sunlight <ul><li>Living things must gain external energy in order to counteract the increase in their entropy </li></ul><ul><li>Photosynthetic organisms use external solar energy to maintain orderly structure </li></ul><ul><li>Non-photosynthetic organisms use stored chemical energy in other living things to counter increasing entropy </li></ul>
  4. 5. Exergonic Reactions (a) Burning glucose (sugar): an exergonic reaction Activation energy needed to ignite glucose Glucose + O 2 Energy released by burning glucose C O 2 + H 2 O Energy content of molecules high low Progress of reaction
  5. 6. Exergonic Reactions Energy Released + + High Energy Reactants Low Energy Products OH O O CH 2 OH O O O O C O H H
  6. 7. Endergonic Reactions (b) Photosynthesis: an endergonic reaction Glucose Net energy captured by synthesizing glucose CO 2 + H 2 O Activation energy from light captured by photosynthesis Energy content of molecules high low Progress of reaction
  7. 8. Endergonic Reactions + Low Energy Reactants + High Energy Products OH O O CH 2 OH O O O O C O H H Energy Supplied
  8. 9. Coupled Reactions
  9. 10. Phosphorylation & ATP = =
  10. 11. ATP versus ADP: Structural Differences ~ DiPhosphate TriPhosphate ADP ATP High-energy Phosphate Bond OH P O O O P OH OH O ~ Ribose H 2 C H O H OH OH H H N HC N C C C CH N N NH 2 Adenine P OH OH O OH P O O O P O OH O ~ Ribose H 2 C H O H OH OH H H N HC N C C C CH N N NH 2 Adenine
  11. 12. Coupled Reactions within Living Cells
  12. 13. Electron Carriers
  13. 14. Metabolic Pathways A B C F G Enzyme 1 Enzyme 2 Enzyme 3 Enzyme 4 Enzyme 5 Enzyme 6 Initial Reactants Intermediates Final Products Pathway 1 Pathway 2 D E
  14. 15. Activation Energy: Controls Rate of Reaction Activation energy without catalyst Activation energy with catalyst Energy content of molecules high low Progress of reaction
  15. 16. Enzyme-Substrate Interactions Substrate Substrate Enzyme Active Site 1 Substrates enter active site 2 Shape change promotes reaction <ul><li>Product released; enzyme ready again </li></ul>
  16. 17. Enzyme Regulation: Feedback Inhibition Enz. 5 D Enz. 4 C Enz. 3 B Enz. 2 A Enz. 1 Threonine (substrate) Isoleucine (end product) Feedback Inhibition Isoleucine inhibits enzyme 1 CH 3 C C COOH OH NH 3 H H CH 2 C C COOH CH 3 NH 3 H H CH 3
  17. 18. Enzyme Regulation: Allosteric Regulation & Competitive Inhibition Substrate Enzyme Active Site Allosteric Regulatory Site (a) Allosteric Regulatory Molecule Shape of active site changed (b) (c) Competitive inhibitor occupies active site
  18. 19. Environmental Conditions <ul><li>Three-dimensional structure of an enzyme is sensitive to pH, salts, temperature, and presence of coenzymes </li></ul><ul><li>Enzyme structure is distorted and function is destroyed when pH is too high or low </li></ul><ul><li>Salts in an enzyme’s environment can also destroy function by altering structure </li></ul>
  19. 20. Environmental Conditions <ul><li>Temperature also affects enzyme activity </li></ul><ul><ul><li>Low temperatures slow down molecular movement </li></ul></ul><ul><ul><li>High temperatures cause enzyme shape to be altered, destroying function </li></ul></ul><ul><ul><li>Most enzymes function optimally only within a very narrow range of these conditions </li></ul></ul>
  20. 23. The end