1. Glycolysis is a metabolic pathway that converts glucose into pyruvate through a two-phase process requiring 10 enzyme-catalyzed steps. 2. In the preparatory phase, energy is invested to phosphorylate and convert glucose into two molecules of glyceraldehyde-3-phosphate. 3. The payoff phase generates energy as glyceraldehyde-3-phosphate is oxidized and converted to pyruvate, producing a net yield of 2 ATP, 2 NADH, and 2 pyruvate molecules from each original glucose molecule.

1. Chemistry of
GLYCOLYSIS
NAFIH AFTHAB V K

2. Glucose
 Glucose is a sugar with the molecular
formula C6H12O6
 Glucose molecules can exist in either
an open-chain (acyclic) or ring (cyclic)
form

3. Adenosin Diphosphate
(ADP)
Adenosin Triphosphate
(ATP)

4. Glycolysis
 Glycolysis is a metabolic pathway that converts the six-carbon glucose
into two molecules of three-carbon pyruvate
 At the end of glycolysis we will have 2 molecules of pyruvate, 2 NADH, and
2 ATP

5. ( 10 Steps)
Preparatory Phase Pay-Off Phase
• First five steps
• Phosphorylation of glucose and its
conversion to glyceraldehyde 3-
phosphate
• Energy is invested in the form of
ATP. (2 ATP is consumed)
• Next five steps
• Conversion of glyceraldehyde 3-
phosphate to pyruvate
• Energy gain occurs. (4 ATP is
produced)

6. Preparatory Phase
Phosphorylation of Glucose
Conversion of Glucose 6-Phosphate to Fructose 6 -Phosphate
Phosphorylation of Fructose 6-Phosphate to Fructose 1,6-
Bisphosphate
Cleavage of Fructose 1,6-Bisphosphate
Interconversion of the Triose Phosphates

7. Phosphorylation of Glucose
• Glucose is activated for subsequent reactions by its phosphorylation at C-6 to yield
glucose 6-phosphate, with ATP as the phosphoryl donor
• Catalyzed by the enzyme hexokinase and 1 ATP is used
1

8. Conversion of Glucose 6-Phosphate to Fructose 6 -
Phosphate
2
• The enzyme phosphohexose isomerase catalyzes the reversible isomerization of
glucose 6-phosphate, an aldose, to fructose 6-phosphate, a ketose

9. Phosphorylation of Fructose 6-Phosphate to
Fructose 1,6-Bisphosphate
3
• Phosphofructokinase-1 (PFK-1) catalyzes the transfer of a phosphoryl group from ATP to
fructose 6-phosphate to yield fructose 1,6-bisphosphate
• 1 ATP is used

10. Cleavage of Fructose 1,6-Bisphosphate
4
• Fructose 1,6-bisphosphate is cleaved to yield two different triose phosphates,
glyceraldehyde 3-phosphate, an aldose, and dihydroxyacetone phosphate, a ketose

11. Interconversion of the Triose Phosphates
5
• Only glyceraldehyde 3-phosphate, can be directly degraded in the subsequent steps of
glycolysis.
• The other product, dihydroxyacetone phosphate, is rapidly and reversibly converted to
glyceraldehyde 3-phosphate by the fifth enzyme of the sequence, triose phosphate
isomerase
• At the end of preparatory phase we have two molecule of glyceraldehyde 3-
phosphate

12. Payoff Phase
Oxidation of Glyceraldehyde 3-Phosphate to 1,3
Bisphosphoglycerate
Phosphoryl Transfer from 1,3-Bisphosphoglycerate to ADP
Conversion of 3-Phosphoglycerate to 2-Phosphoglycerate
Dehydration of 2-Phosphoglycerate to Phosphoenolpyruvate
Transfer of the Phosphoryl Group from Phosphoenolpyruvate
to ADP

13. Oxidation of Glyceraldehyde 3-Phosphate to 1,3
Bisphosphoglycerate
6
• The first step in the payoff phase is the oxidation of glyceraldehyde 3 phosphate to 1,3-
bisphosphoglycerate, catalyzed by glyceraldehyde 3- phosphate dehydrogenase

14. Phosphoryl Transfer from 1,3-Bisphosphoglycerate to ADP
7
• The enzyme phosphoglycerate kinase transfers phosphoryl group from the carboxyl
group of 1,3-bisphosphoglycerate to ADP, forming ATP and 3- phosphoglycerate

15. Conversion of 3-Phosphoglycerate to 2-Phosphoglycerate
8
• The enzyme phosphoglycerate mutase catalyzes a reversible shift of the phosphoryl
group between C-2 and C-3 of glycerate.
• Mg2+ is essential for this reaction

16. Dehydration of 2-Phosphoglycerate to Phosphoenolpyruvate
9
• The enolase promotes reversible removal of a molecule of water from 2-phosphoglycerate to yield
phosphoenolpyruvate (PEP)

17. Transfer of the Phosphoryl Group from Phosphoenolpyruvate
to ADP
10
• The last step in glycolysis is the transfer of the phosphoryl group from
phosphoenolpyruvate to ADP, catalyzed by pyruvate kinase, which requires K+ and either
Mg2+or Mn2+