Glycolysis is a major process from the biological and biochemical aspect. It is the common pathway for both aerobic and anaerobic condition.

1. GURU NANAK INSTITUTE OF PHARMACEUTICAL
SCIENCE & TECHNOLOGY

2. CONTENTS
 Introduction
 Phases of the Glycolysis
 Schematic pathway of the Glycolysis
 Stepwise reactions of the Glycolysis
 Fate of the Pyruvate
 Energetics
 Regulation
 Conclusion
 Bibliography

3. INTRODUCTION
 The term ‘GLYCOLYSIS’ has originated from the Greek words, ‘glykys’ for
sugar and ‘lysis’ for splitting or breakdown.
 Glycolysis is the sequence of 10 enzyme-catalyzed reactions, in which one
molecule of glucose is partially oxidized to form two molecules of Pyruvic acid.
 It occurs in the cytoplasm of the cell and present in all living organism.
 This pathway occurs aerobically as well as anaerobically and common pathway
for all the organism. In case of anaerobic organism, it includes formation of
Lactate from Pyruvate. In aerobic organism, glycolysis is the prelude to TCA
Cycle and ETC.
 Glycolysis is the principal route for carbohydrate metabolism.
 The scheme of glycolysis was given by Gustav Embden, Otto Meyerhof, and J.
Parnas, and is often referred as EMP Pathway.

4. PHASES OF THE GLYCOLYSIS
 Glycolysis leads to breakdown of 6-C glucose into two molecules of 3-C pyruvate with
the enzyme catalyzed reactions that can be divided into 2 phases:- 1) Phase 1-
Preparatory Phase. 2) Phase 2- Payoff Phase.
Preparatory Phase Payoff Phase

5. SCHEMATIC PATHWAY OF
GLYCOLYSIS

6. STEPWISE REACTIONS OF GLYCOLYSIS
Glucose Glucose-6-phosphate
Hexokinase/Glucokinase
AT
P
ADP+P
i
Phosphohexose
Isomerase
Fructose 6-phosphate
Fructose 1,6-
bisphosphate
Phosphofructokinase
AT
P
ADP
+Pi
Glyceraldehyde 3-
Phosphate
Dihydroxyacetone
Phosphate
Triosephosphate Isomerase
Aldolase

7. STEPWISE REACTIONS OF GLYCOLYSIS
(2) x Glyceraldehyde 3-
Phosphate
(2) x 1,3-
bisphosphoglycerate
Glyceraldehyde 3-
Phosphate dehydrogenase
2 NAD+
2 NADH
+ H+
(2) x 3-
phosphoglycerate
Phosphoglycerate kinase
2 x
AT
P
2 x
ADP+P
i
(2) x 2-
phosphoglycerate
Mutase
(2) x
Phosphoenolpyruvate
H2O
(2) x Pyruvate
Enolase
Pyruvate kinase
2 x
AT
P
2 x
ADP+P
i

8. FATE OF THE PYRUVATE
 After the formation of Pyruvate, there are two pathways based on the availability of
oxygen:-
 Under anaerobic condition pyruvate is reduced to lactate by lactate dehydrogenase. It is
also reduced to Ethanol (along with CO2) by pyruvate decarboxylase and alcohol
dehydrogenase.
 Under aerobic condition, pyruvate is transported to mitochondria and undergoes
oxidative decarboxylation by pyruvate dehydrogenase to form Acetyl-CoA, then
oxidation to CO2 in the TCA Cycle.

9. ENERGETICS
STEP NO. REACTION CONSUMPTION OF
ATP
GAIN OF ATP
1 Glucose Glucose 6-phosphate 1 -
2 Fructose 6-phosphate Fructose 1,6-
phosphate
1 -
6 Glyceraldehyde 3-phosphate 1,3-
bisphosphoglycerate
- (2.5x2)=5
[by respiratory chain
oxidation of 2 NADH]
7 1,3-bisphosphoglycerate 3-
Phosphoglycerate
- (1x2)=2
[by substrate-level
phosphorylation]
10 Phosphoenolpyruvate Pyruvate - (1x2)=2
[by substrate-level
phosphorylation]
TOTAL 2 9
*Net gain of ATP = (9-2) = 7
**In case of anaerobic condition, produced NADH is utilized and hence the net gain of
ATP turns out to be only 2.

10. REGULATION
 Glycolysis is mainly regulated b:- i) Enzymatic regulation ii) Hormonal regulation.
i) Enzymatic regulation: Three enzymes regulates the glycolysis majorly. They are
Hexokinase/Glucokinase, Phosphofructokinase & Pyruvate kinase. Hexokinase is
allosterically inhibited by Fructose 6-phosphate whereas, Glucokinase is activated by insulin
and inhibited by glucagon. Similarly Pyruvate kinase is also activated by insulin and inhibited
by glucagon.
ii) Hormonal regulation: Glycolysis is stimulated by insulin whereas, it is inhibited by
glucagon & epinephrine.

11. CONCLUSION
 The overall reactions of Glycolysis can be summarized as:
Glucose + 2Pi + 2ADP + 2NAD+ 2Pyruvate + 2NADH + 2ATP + 2H+ + 2H2O
Thus, the simultaneous reactions involved in Glycolysis are:
 Glucose is oxidized to Pyruvate.
 NAD+ is reduced to NADH.
 ADP is phosphorylated to ATP.

12. BIBLIOGRAPHY
 HARPER’S ILLUSTRATED BIOCHEMISTRY(30TH EDTION)- Victor W.
RODWELL, David A. BENDER, Kathleen M. BOTHAM, Peter J. KENNELLY, P.
Anthony WEIL.
 LEHNINGER PRINCIPLES OF BIOCHEMISTRY(5TH EDITION)- David L.
Nelson, Michael M. Cox.