Biology 172 Lecture 6

  1. Less enzyme results in a ....
    lower Vmax (fewer products in a given time) (fewer active sites)
  2. Rate of reaction increases as ...
    increase [S] to a maximum rate (velocity, Vmax)
  3. Enzyme Regulation
    • Environmental Factors
    • Irreversible Inhibition
    • Reversible Inhibition
    • Allosteric Enzymes
  4. Temperature will affect the ____ _____ of the substrates
    kinetic energy
  5. Irreversible inhibition
    • inhibitor binds to enzyme by covalent bonds, conformation is altered
    • e.g nerve gas
  6. Reversible Inhibition
    • Competive inhibitor
    • Noncompetive inhibitor
  7. Competitive inhibition directly ...
    blocks the active site
  8. Competivite inhibitor
    • Compete with S for active site of enzyme Often resemble S
    • Bind to enzyme with weaker bonds
  9. Some antibiotics, anticancer drugs, herbicides, pesticides To design the inhibitor must
    have knowledge of active site / "S" structure
  10. noncompetitive inhibitors
    • Molecule binds away from active site and alters active site function
    • NOT overcome by changes in substrate concentration (i.e Vmax will be LOWER)
    • Reversible and non-reversible (covalent modification enzyme)
  11. Allosteric regulation occurs when ...
    a regulatory molecule binds away from the active site.
  12. Allo = dteric =
    other site
  13. An Enzyme's Activity is ..
    Percisely Regulated
  14. Enzymes are limited in their catalytic flexibility by the chemistry provided by ....
    the R-group of amino acids. For example, none of the R-groups can absorb visible light, or bind oxygen (O2) as a carrier.
  15. Cofactors and Coenzymes are additional ...
    non-protein factors that can work with protein to provide a broader range of chemistries at active sites, allowing enzymes to catalyze a wider range of reactions
  16. Cofactors are ...
    • small non-protein molecules required for an enzyme to function normally.
    • Usually inorganic (metal) ions
  17. Coenzymes are ...
    • Organic cofactors: NAD, CoA, vitamins
    • Derived form vitamins - hence the dietary requirement
    • Provide enzymes with a broader range of catalytic reactions
  18. Most drugs are ...
    • Competitive inhibitors
    • Most of the rest are non-competitive inhibitors
  19. The mevalonate pathway ...
    synthesizes cholesterol and many other metabolites
  20. HMG-CoA .
    reductase is an enzyme that catalyzes the first step in the pathway
  21. Lipitor (statins)
    • HMG-CoA reductase uses HMG-CoA as a substrate
    • Decreases blood cholesterol.
    • Its mechanism of action is to inhibit cellular synthesis of cholesterol.
    • When cellular synthesis of cholesterol is decreased with Lipitor, cells respond by taking up cholestrol from the blood
  22. Statins
    Lipitor, Zocor, Crestor, Pravachol are all competitive inhibitors of HMG-CoA reductase
  23. HIV
    • Reverse transcriptase is a key enzyme for HIV replication
    • Multiple AIDS drug target this enzyme for inhibition
  24. AZT
    competitive inhibitor, binds at active site
  25. efavirenz
    non-competitive inhibitor, binds adjacent to active site
  26. 4 groups of Lipids
    • Fatty Acids
    • Triglycerides
    • Phospholipids
    • Other Lipids
  27. Lipids
    • Not polymers
    • Mostly composed of hydrocarbon
    • Mostly hydrophobic
    • Fuel storage, membranes, hormones
    • Very diverse class of biological molecules. Waves, some pigments, vit A, vit D, cholesterol
    • Store a LOT of energy - so release a lot of energy when broken down
  28. Fatty Acids
    • Hydrocarbon chains with terminal carboxyl group
    • May be saturated (no double bonds) or unsaturated (with double bonds)
    • Not water soluble
  29. Double-bonds in fatty acids determines ______
  30. Saturated
    • no double-bonds in hydrocarbon chain
    • solid at room temperature
  31. unsaturated
    • double-bonds in hydrocarbon chain
    • liquid or oil = more fluid
  32. Fat =
    glycerol linked by ester linkages to 3 acids
  33. synthesis =
    condensation (dehydration) reaction
  34. Ester
    linkage between glycerol and a fatty acid
  35. Triglycerides =
    Triacylglycerol = fats
  36. Phospholipids =
    • like triacylglycerides, but phosphate-containing compound replaces one fatty acid
    • Have polar part (hydrophilic hear) and a non-polar part (hydrophobic tail)
    • major component of membranes / make membranes
  37. Amphipathic =
    both hydrophilic and hydrophobic regions
  38. 2 ways to transport across membranes
    • Passive Transport
    • Active Transport
  39. Biological Membrnaces
    • provide permeability barriers for the cell
    • composed of lipid bilayer (mostly phospholipids)
  40. What affect membrane permeability
    • Length and degree of saturation of the phospholipid tails
    • Cholesterol
    • Temperature
  41. Membranes possess a fluid quality
    • Phospholipids "drift" within one side of the bilayer
    • Fluidity and permeability is enhanced by unsaturated fatty acid tails
    • cholesterol (a steroid) stabilizes the membrane
  42. Cholesterol
    • Amphipathic
    • Stabilizes membranes by interacting with fatty acid tails of phospholipids
  43. Membranes vary in composition
    • From one species to another
    • From one organelle type to another
    • Phospholipids are different on each side of the bilayer
    • Proteins are different on each side of the bilayer
    • Different inside and outside faces
    • Different lipids in the bilayer and different proteins on the cytoplasmic and extracellular sides of the membrane
  44. Outside layer of the vesicle becomes ...
    cytoplasmic side when it fuses
  45. Inside face of ER/ Golgi becomes ...
    outside (extracellular) face of plasma membrane
Card Set
Biology 172 Lecture 6
Biology 172 Lecture 6 exam review