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Cell Metabolism Part 1


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Cell Metabolism Part 1

  1. 1. Ch 4: Cellular Metabolism, Part 1 <ul><li>Energy as it relates to Biology </li></ul><ul><ul><li>Energy for synthesis and movement </li></ul></ul><ul><ul><li>Energy transformation </li></ul></ul><ul><li>Enzymes and how they speed reactions </li></ul><ul><li>Metabolism and metabolic pathways </li></ul><ul><ul><li>Catabolism (ATP production) </li></ul></ul><ul><ul><li>Anabolism ( Synthesis of biologically important molecules ) </li></ul></ul>
  2. 2. Energy in Biol. Systems: <ul><li>General definition of energy: Capacity to do work </li></ul><ul><ul><li>Chemical, transport, movement </li></ul></ul><ul><li>First Law of Thermodynamics: Energy can neither be created nor destroyed </li></ul><ul><li>Ultimate source of energy: Sun! </li></ul>Fig 4-2 2 types of energy: <ul><li>Kinetic energy = motion </li></ul><ul><ul><li>examples ? </li></ul></ul><ul><li>Potential energy = stored energy </li></ul><ul><ul><li>examples ? </li></ul></ul>
  3. 3. Energy (E) Transfer Overview Figure 4-1
  4. 4. Potential Energy Kinetic Energy WORK heat (~ 70% of energy used in physical exercise)
  5. 5. Bioenergetics = study of energy flow through biol. systems <ul><li>Chemical reactions transfer energy </li></ul><ul><li>A + B C + D </li></ul>Substrates or reactants Products Speed of reaction = Reaction rate Initial force = Activation Energy
  6. 6. Potential Energy Stored in Chemical Bonds of Substrate can be . . . <ul><li>transferred to the chemical bonds of the product </li></ul><ul><li>released as heat (usually waste) </li></ul><ul><li>used to do work ( = free energy) </li></ul>
  7. 7. Chemical Reactions p 93 <ul><li>Activation energy </li></ul><ul><li>Endergonic vs. exergonic reactions </li></ul><ul><li>Coupled reactions </li></ul><ul><ul><li>Direct coupling vs. indirect coupling </li></ul></ul><ul><li>Reversible vs. irreversible reactions </li></ul>
  8. 8. Activation Energy Fig 4-3
  9. 9. Endo- and Exergonic Reactions Which is which?? ATP + H 2 O ADP + P i + H + + Energy
  10. 10. Enzyme (= Biol. Catalyst) <ul><li>Enzymes are proteins </li></ul><ul><li> rate of chemical reaction by lowering activation energy </li></ul><ul><li>is not changed itself </li></ul><ul><ul><li>It may change DURING the reaction </li></ul></ul><ul><li>does not change the nature of the reaction nor the result </li></ul><ul><li>is specific </li></ul>Some important characteristics of an enzyme: Fig 4-6
  11. 12. Enzymes lower activation energy: All chemical reactions in body must be conducted at body temp.!! How do enzymes lower activation energy ?
  12. 13. <ul><li>Enzymes bind to reactant molecules and bring them together in best position for rx. </li></ul>
  13. 14. Some more characteristics of enzymes: <ul><li>Usually end in –ase </li></ul><ul><li>Inactive form: -ogen </li></ul><ul><li>in few cases RNA has enzymatic activity (eg: rRNA  peptide bond) </li></ul><ul><li>Isoenzymes may be produced in different areas of the body </li></ul><ul><ul><li>E.g., LDH </li></ul></ul>
  14. 15. <ul><li>Small region of the complex 3D structure is active (or binding) site. </li></ul><ul><li>Enzymes bind to substrate </li></ul>Active Site: Old: Lock-and-key model / New: Induced-fit model
  15. 16. Enzyme-substrate interaction: The old and the new model Lock and Key: Induced fit:
  16. 17. Enzyme Specificity <ul><li>Often: reaction with only one substrate </li></ul><ul><li>Sometimes: reaction with group of similar substrates </li></ul>
  17. 18. Naming of Enzymes <ul><li>Kinase </li></ul><ul><li>Phosphatase </li></ul><ul><li>Peptidase </li></ul><ul><li>Dehydrogenase </li></ul>mostly suffix -ase first part gives info on function examples
  18. 19. Isoenzymes = different models of same enzyme (differ in 1 or few aa) <ul><li>Examples: </li></ul><ul><li>Amylase </li></ul><ul><li>LDH -> importance in diagnostics </li></ul>Catalyze same reaction but under different conditions and in different tissues/organs
  19. 20. Enzyme Activity depends on <ul><li>Proteolytic activation (for some) </li></ul><ul><li>Cofactors & coenzymes (for some) </li></ul><ul><li>Temperature </li></ul><ul><li>pH </li></ul><ul><li>Other molecules interacting with enzyme </li></ul><ul><ul><li>Competitive inhibitors </li></ul></ul><ul><ul><li>Allosteric modulators </li></ul></ul>
  20. 21. 1) Proteolytic Activation <ul><li>Also </li></ul><ul><li>Pepsinogen Pepsin </li></ul><ul><li>Trypsinogen Trypsin </li></ul>
  21. 22. 2) Cofactors & Coenzymes structure: Inorganic molecules (?) function: conformational change of active site structure: Organic molecules (vitamin derivatives, FADH 2 ....) function: act as receptors & carriers for atoms or functional groups that are removed from substrate
  22. 23. Cofactors bind to active site
  23. 24. 3) Breakage of intramolecular bonds lead to ?
  24. 25. <ul><li>Tyrosine Melanin </li></ul><ul><li>Tyrosinase is temperature sensitive  does not function at cat’s core body temperature (101.5° F) </li></ul>Siamese Cats tyrosinase
  25. 26. 3)
  26. 27. 4) Molecules interacting with enzyme <ul><li>Competitive inhibitors : bind to active site </li></ul>block active site E.g.: Penicillin binds covalently (= irreversibly to important bacterial enzyme active site) Fig 4-13
  27. 28. 4) Molecules interacting with enzyme, cont’d <ul><li>Allosteric modulators (fig 4-14) : bind to enzyme away from active site change shape of active site (for better or for worse) </li></ul>= end product inhibition Special case:
  28. 29. Allosteric Modulation
  29. 30. Reaction Rate Depends on Enzyme & Substrate Concentration
  30. 31. Reversible Reactions follow the Law of Mass Action
  31. 32. Three Major Types of Enzymatic Reactions: <ul><li>Oxydation - Reduction reactions </li></ul><ul><ul><li>(transfer of electrons or protons (H + )) </li></ul></ul><ul><li>Hydrolysis - Dehydration reactions </li></ul><ul><ul><li>(breakdown & synthesis of water) </li></ul></ul><ul><li>Addition-Subtraction-Exchange (of a functional group) reactions </li></ul>
  32. 34. ?
  33. 35. Metabolism Catabolism Anabolism next time