1. Fundamentals of Biochemistry
Third Edition
Donald Voet • Judith G. Voet • Charlotte W. Pratt
Chapter 15
Glucose Catabolism
Copyright © 2008 by John Wiley & Sons, Inc.

2. Overview of Glycolysis

3. Step 1
Not really that reversible

4. Hexokinase

5. Step 2

6. Step 3

7. Step 4

8. Step 5

9. Step 6

10. Determination of the Mechanism

12. Step 7

13. Step 8

14. Figure 15-12

15. Step 9

16. Step 10

18. What did we accomplish?
Overall, we took 1 glucose molecule and made: 2 pyruvates, 2 NADH, 2 ATP, and 2 H2O
Net equation

19. Fates of Pyruvate

20. Lactate Dehydrogenase (LDH)

21. Alcoholic Fermentation by Yeast

22. Energy Efficiency ΔG°’ = -196 kJ/mol ΔG°’ = -235 kJ/mol
To make 2 ATP = ΔG°’ = 61 kJ/mol
Therefore, lactate production is 61/196 = 31% efficient
Therefore, ethanol production is 61/235 = 26% efficient
Under biochemical concentrations, the reactions are actually >50% efficient

24. Regulation of Glycolysis

25. PFK is main regulatory enzyme
Activators: ADP; AMP; F2,6P
Other substrate: F6P
Substrate/inhibitor = ATP

26. Other Mechanisms Is flux controlled only by ATP?
Seems like yes, but no
Glycolytic flux varies by 100 fold
ATP concentration varies only 10 fold
ATP concentration is buffered by other enzymes such as creatine kinase and adenylate kinase
However, [ATP] is 50X > [AMP] and 10x > [ADP]
Therefore, a 10% change in [ATP] and result in 100% change of ADP and 400% change of AMP

27. Substrate cycling
A ↔ B
If top equation were correct, then thermodynamics would be violated. One enzyme cannot be favorable in two directions
Substrate cycling uses two different enzymes.

28. Substrate cycling
PFK
FBPase

29. Other Hexoses

33. Pentose Phosphate Pathway
Stage 1
Stage 2
Stage 3

34. Figure 15-34

35. Figure 15-35