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13.2 - Glycolysis, Reactions, Fate of Pyruvate

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  1. Front
    Glycolysis
    Back
    Breakdown of glucose into pyruvate
  2. Front
    Location of glycolysis
    Back
    Cytosol
  3. Front
    Oxygen requirement of glycolysis
    Back
    Does not require oxygen and can occur in both aerobic and anaerobic conditions
  4. Front
    Main outputs of glycolysis from 1 glucose
    Back
    2 pyruvate, ATP, and NADH
  5. Front
    Role of glycolysis in glucose metabolism
    Back
    First step of glucose oxidation
  6. Front
    Importance of glycolysis in some cells
    Back
    It is the only source of ATP in some cells such as red blood cells
  7. Front
    Two phases of glycolysis
    Back
    Energy investment phase and energy payoff phase
  8. Front
    Energy investment phase of glycolysis
    Back
    Steps 1–5 that use ATP and prepare glucose for splitting
  9. Front
    Energy payoff phase of glycolysis
    Back
    Steps 6–10 that produce ATP and NADH
  10. Front
    Net result of glycolysis per glucose
    Back
    2 ATP net, 2 NADH, and 2 pyruvate
  11. Front
    Core logic of glycolysis
    Back
    Energy is invested first, the molecule is split, and then more energy is gained back
  12. Front
    Step 1 of glycolysis
    Back
    Glucose → glucose-6-phosphate
  13. Front
    Enzyme of step 1 in most tissues
    Back
    Hexokinase
  14. Front
    Enzyme of step 1 in liver
    Back
    Glucokinase
  15. Front
    Energy use in step 1
    Back
    Uses ATP
  16. Front
    Reversibility of step 1
    Back
    Irreversible
  17. Front
    Why step 1 matters
    Back
    Traps glucose in the cell and commits it to metabolism
  18. Front
    Regulation of hexokinase
    Back
    Hexokinase is inhibited by glucose-6-phosphate
  19. Front
    Step 2 of glycolysis
    Back
    Glucose-6-phosphate → fructose-6-phosphate
  20. Front
    Enzyme of step 2
    Back
    Phosphoglucose isomerase
  21. Front
    Purpose of step 2
    Back
    Prepares the molecule for phosphorylation at carbon 1
  22. Front
    Step 3 of glycolysis
    Back
    Fructose-6-phosphate → fructose-1,6-bisphosphate
  23. Front
    Enzyme of step 3
    Back
    Phosphofructokinase-1 (PFK-1)
  24. Front
    Energy use in step 3
    Back
    Uses ATP
  25. Front
    Reversibility of step 3
    Back
    Irreversible
  26. Front
    Rate-limiting step of glycolysis
    Back
    Phosphofructokinase-1 step
  27. Front
    Most important regulatory step of glycolysis
    Back
    PFK-1 converting fructose-6-phosphate to fructose-1,6-bisphosphate
  28. Front
    Why PFK-1 is important
    Back
    It controls the speed of glycolysis and is highly regulated
  29. Front
    Commitment step of glycolysis
    Back
    Conversion of fructose-6-phosphate to fructose-1,6-bisphosphate by PFK-1
  30. Front
    Meaning of commitment step
    Back
    Once fructose-1,6-bisphosphate is formed, glucose will proceed through glycolysis
  31. Front
    Step 4 of glycolysis
    Back
    Fructose-1,6-bisphosphate splits into glyceraldehyde-3-phosphate and dihydroxyacetone phosphate
  32. Front
    Enzyme of step 4
    Back
    Aldolase
  33. Front
    Products of step 4
    Back
    Glyceraldehyde-3-phosphate (G3P) and dihydroxyacetone phosphate (DHAP)
  34. Front
    Step 5 of glycolysis
    Back
    DHAP ↔ G3P
  35. Front
    Enzyme of step 5
    Back
    Triose phosphate isomerase
  36. Front
    Purpose of step 5
    Back
    Converts DHAP into G3P
  37. Front
    Result after step 5 from one glucose
    Back
    2 molecules of G3P are produced
  38. Front
    Why later glycolysis reactions happen twice per glucose
    Back
    One glucose yields two G3P molecules
  39. Front
    Step 6 of glycolysis
    Back
    G3P → 1,3-bisphosphoglycerate
  40. Front
    Events in step 6
    Back
    Oxidation occurs, NAD⁺ is reduced to NADH, and phosphate is added
  41. Front
    Source of phosphate in step 6
    Back
    The phosphate is not donated by ATP
  42. Front
    Importance of step 6
    Back
    It is the step where NADH is produced
  43. Front
    Requirement for step 6
    Back
    NAD⁺ is required
  44. Front
    Effect of lack of NAD⁺ on glycolysis
    Back
    Glycolysis stops without NAD⁺
  45. Front
    Step 7 of glycolysis
    Back
    1,3-bisphosphoglycerate → 3-phosphoglycerate
  46. Front
    Main event in step 7
    Back
    ATP is generated
  47. Front
    Type of ATP formation in step 7
    Back
    Substrate-level phosphorylation
  48. Front
    Substrate-level phosphorylation
    Back
    Making ATP directly from a metabolic intermediate
  49. Front
    First ATP-producing step of glycolysis
    Back
    Step 7
  50. Front
    Step 8 of glycolysis
    Back
    3-phosphoglycerate → 2-phosphoglycerate
  51. Front
    Step 9 of glycolysis
    Back
    2-phosphoglycerate → phosphoenolpyruvate
  52. Front
    High-energy intermediate formed in step 9
    Back
    Phosphoenolpyruvate (PEP)
  53. Front
    Importance of PEP
    Back
    High-energy molecule used in the final ATP-generating step
  54. Front
    Step 10 of glycolysis
    Back
    PEP → pyruvate
  55. Front
    Enzyme of step 10
    Back
    Pyruvate kinase
  56. Front
    ATP production in step 10
    Back
    Produces ATP
  57. Front
    Reversibility of step 10
    Back
    Irreversible
  58. Front
    Second ATP-producing step of glycolysis
    Back
    Step 10 catalyzed by pyruvate kinase
  59. Front
    ATP accounting in glycolysis per glucose
    Back
    2 ATP are used early, 2 ATP are produced at step 7, and 2 ATP are produced at step 10
  60. Front
    Net ATP from glycolysis per glucose
    Back
    2 ATP
  61. Front
    Conceptual overall reaction of glycolysis
    Back
    Glucose → 2 pyruvate + ATP + NADH
  62. Front
    Net yield of glycolysis per glucose
    Back
    2 ATP net, 2 NADH, and 2 pyruvate
  63. Front
    Irreversible steps of glycolysis
    Back
    Hexokinase, PFK-1, and pyruvate kinase
  64. Front
    Most important irreversible step of glycolysis
    Back
    PFK-1
  65. Front
    Aerobic glycolysis
    Back
    Glycolysis in the presence of oxygen, where NADH can go to mitochondria for further ATP production
  66. Front
    Anaerobic glycolysis
    Back
    Glycolysis without oxygen, where NADH must be recycled to NAD⁺ by lactate formation
  67. Front
    Why NAD⁺ regeneration matters in glycolysis
    Back
    Glycolysis requires NAD⁺ to continue
  68. Front
    Lactate formation
    Back
    Pyruvate → lactate
  69. Front
    Enzyme for lactate formation
    Back
    Lactate dehydrogenase
  70. Front
    Redox change in lactate formation
    Back
    NADH is oxidized to NAD⁺
  71. Front
    Purpose of lactate formation
    Back
    Regenerates NAD⁺ so glycolysis can continue without oxygen
  72. Front
    Key idea of lactate formation
    Back
    It serves as an NAD⁺ regeneration system
  73. Front
    Cori cycle
    Back
    Muscle produces lactate, lactate goes to the liver, and the liver converts lactate back to glucose
  74. Front
    Function of the Cori cycle
    Back
    Prevents lactate buildup and helps maintain blood glucose
  75. Front
    Aerobic fate of pyruvate
    Back
    Pyruvate is converted to acetyl-CoA
  76. Front
    Location of pyruvate to acetyl-CoA conversion
    Back
    Mitochondria
  77. Front
    Oxygen requirement of pyruvate to acetyl-CoA conversion
    Back
    Requires oxygen indirectly
  78. Front
    Importance of acetyl-CoA formation
    Back
    Acetyl-CoA enters the TCA cycle
  79. Front
    How glycolysis leads to major ATP production
    Back
    Pyruvate formed in glycolysis is converted to acetyl-CoA and enters the TCA cycle
  80. Front
    Major fates of pyruvate
    Back
    Lactate under anaerobic conditions and acetyl-CoA under aerobic conditions
  81. Front
    Other fates of pyruvate
    Back
    Less emphasized additional metabolic pathways
  82. Front
    Main factor determining pyruvate fate
    Back
    Oxygen availability and cellular conditions
  83. Front
    Integration role of glycolysis
    Back
    Glycolysis produces pyruvate that feeds into multiple pathways including the TCA cycle
  84. Front
    Final takeaway of glycolysis section
    Back
    Glycolysis always occurs, produces a small amount of ATP, and feeds into larger metabolic pathways
  85. Front
    Glycolysis essentials
    Back
    Occurs in the cytosol, does not require oxygen, and yields 2 ATP net, 2 NADH, and 2 pyruvate
  86. Front
    Three most tested irreversible steps of glycolysis
    Back
    Hexokinase, PFK-1, and pyruvate kinase
  87. Front
    Rate-limiting enzyme of glycolysis
    Back
    PFK-1
  88. Front
    G6P in glycolysis
    Back
    Branch-point intermediate
  89. Front
    Fructose-1,6-bisphosphate in glycolysis
    Back
    Product of the commitment step
  90. Front
    G3P in glycolysis
    Back
    Marks the start of the payoff phase
  91. Front
    PEP in glycolysis
    Back
    High-energy intermediate before pyruvate formation
  92. Front
    NAD⁺ rule in glycolysis
    Back
    Glycolysis stops without NAD⁺
  93. Front
    How anaerobic cells regenerate NAD⁺
    Back
    By converting pyruvate to lactate
  94. Front
    Pyruvate fate in aerobic conditions
    Back
    Converted to acetyl-CoA
  95. Front
    Pyruvate fate in anaerobic conditions
    Back
    Converted to lactate

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