1. Glycolysis: Allowed abbreviations
Glucose
Glucose 6-phosphate
Fructose 6-phosphate
Fructose 1,6-bisphosphate
Dihydroxyacetone phosphate
Glyceraldehyde 3-phosphate
1,3-Bisphosphoglycerate
3-phosphoglycerate
2-phosphoglycerate
Phosphoenolpyruvate
Pyruvate
N/A
G-6P
F-6P
F-1,6BP
DHAP
G-3P
1,3-BPG
3-PG
2-PG
PEP

2. Fates of Other Sugars

5. GLUCONEOGENESIS

7. Synthesis of "new glucose" from common metabolites
Gluconeogenesis
Synthesis of "new glucose" from common metabolites
Humans consume 160 g of glucose per day
75% of that is in the brain
Body fluids contain only 20 g of glucose
Glycogen stores yield g of glucose
So the body must be able to make its own glucose 3

9. Substrates for Gluconeogenesis
Pyruvate, lactate, glycerol, amino acids and all TCA intermediates can be utilized
Fatty acids cannot!
Why?
Most fatty acids yield only acetyl-CoA
Acetyl-CoA (through TCA cycle) cannot provide for net synthesis of sugars 4

10. Gluconeogenesis Occurs mainly in liver and kidneys
Not the mere reversal of glycolysis for 2 reasons:
Energetics must change to make gluconeogenesis favorable (delta G of glycolysis = -74 kJ/mol
Reciprocal regulation must turn one on and the other off - this requires something new! 5

11. Something Borrowed, Something New
Gluconeogenesis
Something Borrowed, Something New
Seven steps of glycolysis are retained:
Steps 2 and 4-9
Three steps are replaced or bypassed:
Steps 1, 3, and 10 (the regulated steps!)
The new reactions provide for a spontaneous pathway (G negative in the direction of sugar synthesis), and they provide new mechanisms of regulation
Make sure you know the THREE BYPASS STEPS of Gluconeogenesis 6

13. 1st bypass reaction:
Pyruvate → PEP
Pyruvate is converted back to PEP in two steps.
Not shown here is the transport process: since oxaloacetate is usually found in the mitochondrial matrix, it must be transported out into the cytosol. However, there is no transporter for oxaloacetate.

14. 1st bypass reaction:
Pyruvate → PEP
Therefore, oxaloacetate is reduced to malate first using malate dehydrogenase.
Malate is transported out into the cytosol and then reoxidized back to oxaloacetate

15. 2nd bypass reaction:
Fructose 1,6-Bisphosphate → Fructose 6-phosphate
Technically the reverse of the glycolytic reaction, but it is mediated by a different enzyme.

16. Mediated by a different enzyme.
2nd bypass reaction:
Glucose 6-Phosphate → Glucose
Mediated by a different enzyme.

17. Cori cycle

19. Pentose Phosphate Pathway