glycolysis - stage 1
- 10 reaction sequence converting glucose to 2 3-carbon molecules of pyruvate
- glucose + 2ADP + 2P + 2NAD+ >> 2 pyruvate + 2ATP + 2NADH + 2H+ + 2H2O
- can be performed by all organisms (doesn't require oxygen or special organelles)
- metabolism evolves by adding reactions to each other, so glycolysis was never replaced
priming - 1st half of glycolysis; makes 2 3-carbon glyceraldehyde 3-phosphates from glucose
- 5 reactions
- step A - glucose priming
- 3 reactions changing glucose into a compound that can be readily cleaved into 3-carbon phosphorylated molecules
- 2 of the reactions require use of ATP
- step B - cleavage/rearrangement
- 2 reactions break up 6-carbon molecule into 2 3-carbon molecules
- 1st of 2 reactions forms G3P and another molecule that turns into G3P through the 2nd reaction
substrate-level phosphorylation - 2nd half of glycolysis; makes pyruvate from G3P
- 5 reactions
- step C - oxidation
- 2 electrons, 1 proton transferred from G3P to NAD+ to make NADH
- step D - ATP generation
- 4 reactions convert G3P to pyruvate, generating 2 ATP
- in total, 4 ATP per glucose molecule produced
- 2 ATP used in beginning, so glycolysis has net ATP gain of 2
- harvests 24 kcal/mol of glucose, about 3.5% of chemical energy in glucose
regeneration of NADH - only a small amount of NAD+ exists in cells
- necessary that the H on NADH be transferred somewhere else
- aerobic respiration - uses oxygen as electron acceptor (takes the H to become H2O); oxidizes pyruvate to acetyl-CoA
- fermentation - uses organic molecule (like acetaldehyde) in place of oxygen; reduces all or part of pyruvate
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