Principles of Biochemistry 4e

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Chapter 12 Gluconeogenesis, Part 1

• Why gluconeogenesis?
• The overall reaction of gluconeogenesis.

• Formation of phosphoenolpyruvate
• from pyruvaate.
• Formation of fructose-6-P
• from fructose-1,6-bis-P
• 5. Formation of glucose from glucose-6-P.
• Regulation of gluconeogenesis.
• The pentose phosphate pathway

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• Why gluconeogenesis?
• A. Recycle lactate from muscle.
• B. Convert amino acids to glucose.
• C. Metabolize glycerol.

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A. Recycle lactate.
Cori cycle.
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• Amino acids - production of pyruvate
• from alanine.

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Overall reaction. 2 pyruvate 2 NADH 4ATP 2
GTP ? Glucose 2 NAD 4ADP 2 GDP 6 P
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3 irreversible reactions in glycolysis.

• Pyruvate kinase
• Phospho- fructokinase
• Hexokinase

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• Formation of phosphoenolpyruvate
• from pyruvate.
• Formation of oxaloacetate from
• puruvate requries biotin.
• B. Formation of phosphoenolpyruvate
• from oxaloacetate.

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A. Formation of oxaloacetate from pyruvate.
Uses the coenzyme biotin
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Oxaloacetate is important in gluconeogenesis als
o helps replenish intermediates of the citric
acid cycle.
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Carboxylases require biotin.
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• Formation of phosphoenolpyrovate
• from oxaloacetate.

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4. Fructose 1,6-bisP ? fructose 6-P
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5. Glucose 6-P to Glucose
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6. Regulation of gluconeogenesis.
Futile cycle substrate cycle
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The hormone glucagon raises blood sugar by 1)
phosphorylating protein kinase A 2) increases
the phosphorylation of PFK-2 3) which
deceases the activity of PFK-2 4) which stops
its activation of PFK-1 and activates PFK
phosphatase Thus, glucagon stimulaates
gluconeogenesis. PFK phosphofructokinase.
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7. Pentose phosphosphate pathway
Produces ribose other pentoses NADPH for
biosynthesis.
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From C F.