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<title>questions 2.33-01, 2.8-99, 2.15-99  </title>
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Where did the phosphates in glycolysis  come from? The handout makes no mention 
of additional ATP molecules being used?     <br></font><font color="#000000">
The 2 phosphates that are added in the phosphorylation of Gal-3-P to 1,3 diPGA 
came from inorganic phosphate (a.k.a. Pi, or   H3PO4,    PO4---). This phosphate 
is present as an inorganic component of   minimal  medium  (potassium phosphate), 
an inorganic salt that is necessary   for life  (in part  for this reason).
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I am having a problem trying to understand what happens to the  
electrons in reaction 6 on the "glycolytic pathway" handout.
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Two hydrogen atoms have been withdrawn from the two reactants.   The
hydrogens leave as hydrogen atoms, not hydrogen ions; thus they leave
with their electrons.  So 1,3-diPGA has 2 less electrons that do the two
reactants, G3P and PO4.  These electrons are accepted by NAD. One of the
electrons is divorced from its proton in the process. That proton
(hydrogen ion) joins the pool of H+ ions in the pH7 milieu of the cell.
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In glycolysis, rxn 6 adds a phosphate group without using energy from
ATP. Does this energy come from reducing NAD to NADH2?
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No, reducing NAD to NADH2 ABSORBS a tremendous amount aof energy (remember
how much you get out (-53 kc/m) when the reverse process occurs in oxidative
phosphorylation). The energy is coming from the oxidation of G3P to
1,3-diPGA (BPG).
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