Carbohydrate processing gluconeogenesis pentose phospate pathway

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Carbohydrate processing gluconeogenesis
pentose phospate pathway
S 2006 BIOC 3406 1-31-2006
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Fates of ingested polysaccharides

• Glycogen or starch H2O ? oligosaccharides,
  dextrins, di- and trisaccharides
• Dextrin n H2O ? n D-glucose (brush border)
• Maltose H2O ? 2 D-glucose
• Lactose H2O ? D-glucose D-galactose
• Sucrose H2O ? D-glucose D-fructose
• Trehalose H2O ? 2 D-glucose

mouth, upper GI
brush border
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Course of digestion

• a-amylase breaks down glycogen/starch
• salivary, pancreatic
• Brush border enzymes break di- and
  tri-saccharides down to monosaccharides for
  absorption

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Mistake in your book
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Galactokinase Deficiency Galactosemia
(This would be a CHO in galactose)
Galactokinase deficiency leads to high galactose
concentrations and the presence of galactitol,
which causes cataracts
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Other galactosemias

• Transferase deficiency
• More serious than GKD Galactosemia
• Poor growth
• Speech problems
• Mental retardation
• Liver damage
• Epimerase deficiency
• Similar to transferase deficiency but less severe
  with control of galactose intake

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Anaerobic fates of pyruvate

• Tied to fate of NADH formed in glycolysis
• O2 should be acceptor of NADHs reducing
  equivalent, but if it is not
• Pyruvate is fermented and NADH ? NAD H
• Lactic acid fermentation
• Ethanol fermentation

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This is resonance but is shown incorrectly. The
two forms do not have different structures
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Pyruvate ATP GTP HCO3- ? PEP ADP GDP
Pi CO2
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(This amounts to feedback inhibition)
AcSCoA
Note addition of CO2
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Followed by loss of CO2
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In the cytosol, NAD/NADH is high, but in
mitochondria NAD/NADH is low.
In cytosol
Important in large mammals (you)
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Note how much it costs to convert pyruvate to
glucose!
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Other paths to glucose

• Citric acid cycle intermediates
• Amino acids

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Pentose phosphate pathway

• Various names
• Pentose pathway
• Phosphogluconate pathway
• Hexose monophosphate pathway
• Oxidative Part
• Produces pentoses, NADPH
• Nonoxidative
• Balances 5,6-ose phosphates

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Nonoxidative phase

• Reshuffling of pentoses to hexoses

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