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Lecture on Gluconeogenesis
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Overview of gluconeogenesis
 Gluconeogenesis is the generation of glucose from other
substrates. Like many metabolic pathways it happens
mostly in the liver, and is triggered by the action of
insulin.
 Gluconeogenesis begins with various substrates converted
into pyruvate.and this proceed though what is essentially
the reverse of glycosis(except for a few committed steps).
 3 and 4-carbon substrates can enter the gluconeogenesis
pathway. Lactate from anaerobic exercise in skeletal
muscle is easily converted to pyruvate; this happens as
part of the Cori cycle.
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Overview of gluconeogenesis
• Oxaloacetate (an intermediate in the citric acid
cycle can also be used for gluconeogenesis. Amino
acids, after their amino group has been removed,
feed into parts of the citric acid cycle, and can thus
can generate glucose in this pathway.
• Fatty acids cannot be turned into glucose, as they
are broken down into the two carbon acetyl CoA.
(However glycerol which is a part of all
triacylglycerides can be used in gluconeogenesis).
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Stage3
Amphibolic
pathway:
a
metabolic pathway that functions
in both anabolism and catabolism
Stage2
Stage1
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-4650
Stage1:to invest 2 ATP
Stage2:to produce
4 ATP and 2NADH
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-2600 -2571
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2 pyruvate + 2ATP + 2NADH + 4H+ +2H2O
=glucose + 2ADP + 2NAD+ + 6Pi
2 pyruvate + 4ATP + 2GTP + 2NADH + 4H+ + 6H2O
=glucose + 4ADP + 2GDP + 2NAD+ + 6Pi
Total: 6 molecules ATP, 2 molecules NADH
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2mol pyruvate
2mol
Phosphoenolpyruvate
2mol 2phosphoglycerate
2mol 3phosphoglycerate
2mol 1,3Bisphosphglycereate
2mol Glyceraldehyde3-phosphate
1 mol Fructose-1,6bisphosphate
1 mol Fructose-6phosphate
1mol Glucose
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DG°' = +73.3 kJ/mol
DG°' = - 47.6 kJ/mol
The special reactions
Pyruvate+ CO2 + H2O + ATP= oxaloacetate ΔGº’ kJ/mol
+ADP+ Pi + 2H+
-2.1
Oxaloacetate+GTP= Phosphoenolpyruvate+
+2.9
CO2 +GDP
Fructose-1,6-bisphosphate+ H2O= Fructose-16.3
6-phosphate+ Pi
Glucose-6-phosphate+ H2O=Glucose+ Pi
-12.1
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Fuitle cycle
glucose + 2ADP + 2NAD+ + 6Pi =2 pyruvate + 2ATP + 2NADH
+ 4H+ + 2H2O
DG°' = -73.3 kJ/mol
2 pyruvate + 4ATP + 2GTP + 2NADH + 4H+ + 6H2O = glucose +
4ADP + 2GDP+ 2NAD++6Pi
DG°' = - 47.6 kJ/mol
Total:2ATP+2GTP+4H2O = 2ADP + 2GDP+6Pi
DG°' = -121 kJ/mol
Fuitle cycle:a set of opposing reactions that can be
arranged in a cycle, but usually do not occur
simultaneously; functioning of such reactions in both
directions is avoided by metabolic control
mechanisms to prevent energy waste.
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Cori cycle
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