by prachee rajput BARKATULLAH UNIVERSITY, BHOPAL (IND)

3. INTRODUCTION
Glycolysis is one of the several catabolic pathways known generally as
anaerobic fermentation, by which many organisms extract chemical
energy from various organic fuels in the absence of molecular oxygen.
Gycolysis in most animals serves as an important emergency mechanism
capable of yielding energy for short period when oxygen is not available.

4. DEFINITION
The term Glycolysis is derived from the Greek word glycos = suger (sweet);
lysis = dissolution is a sequence of an enzyme catalyzed reactions that
convert glucose into pyruvate with the simultaneous production of ATP.
Moreover, glycolysis also includes the formation of lactate from pyruvate in
aerobic organims glycolysis prelude to the citric acid cycle and the electron
transport chain which together harvest most of the energy contained in
glucose from.

5. TYPES OF GLYCOLYSIS
ANAEROBIC GLYCOLYSIS-
From glycogen to glucose to
lactic acid in muscles.it is again
of two types.
1. Homolactic fermentation-the
glucose molecule is
degaded to two molecule of
the three carbon lactic
acid.eg-muscle cells
2. Alcholic fermentation-the
glucose molecule is broken
down into two molecules of
the two carbon compound
ethanol and two molecules
of carbondioxide.eg-yeasts.
AEROBIC GLYCOLYSIS-
from glycogen to glucose to
pyruvic acid in all cells of body
i.e., glucose pyruvic acid
oxidativedecarboxylation
acetyl coA krebs cycle.

6.  There are 10 enzyme-catalyzed reactions considered to occur in
two stages
 Stage I (reactions 1-5): Preparatory stage where glucose is
phosphorylated and cleaved to yield 2 molecules of
glyceraldehyde-3-phosphate (GAP). Stage I uses 2 ATPs.
 Stage II (reactions 6-10) Payoff stage where 2 GAPs converted
to pyruvate and generation of 4 ATPs.
EMBDEN MEYERHOF PARNAS
PATHWAY OVERVIEW

7. GLYCOLYTIC PATHWAY
Stage 1
Stage 2

8. 2. THE REACTIONS OF GLYCOLYSIS
STAGE I (PREPARATORY STAGE)
1. Hexokinase(first ATP utilization)
2. Phosphoglucose Isomerase (PGI)
3. Phosphofructokinase-1 (PFK-1)(second ATP
utilization)
4. Aldolase
5. Triose PhosphateIsomerase (TIM)

10. THE PREPARATORY PHASE
Step 1 –
Hexokinase

11. (A) HEXOKINASE: FIRST ATP UTILIZATION
Reaction 1 of glycolysis is the transfer of a phosphoryl
group from ATP to glucose to form glucose 6-
phosphate(G6P).

12. Step 2 –
Phosphoglucose
Isomerase
(PGI)
[Phosphohexose
isomerase]
Phosphoglucose Isomerase
catalyzes the conversion of
G6P to F6P, the isomerization
of an aldose to a ketose.

13. (C) STEP 3 - PHOSPHOFRUCTOKINASE-1:
 PFK-1 phosphorylates fructose-6-phosphate (F6P) in
reaction 3 of glycolysis (second ATP utilization).
 PFK plays a central role in control of glycolysis because it
catalyzes one of thepathway’s rate-determiningreactions.

14. Step 4 - Aldolase. Aldol cleavage of FBP to form two
Trioses (GAP and DHAP)
Note that the atom
numbering system
changes. Atoms 1, 2,
and 3 of glucose become
atoms 3,2, and 1 of
DHAP. Atoms 4, 5, and
6 become atoms
1, 2, and 3 of GAP.

15. (E) STEP 5 - TRIOSE PHOSPHATE
ISOMERASE (TIM)
Only GAP continues
along the glycolytic
pathway.

16. Fate of the carbon atoms of glucose in the
formation of glyceraldehyde-3-phosphate.

17. STAGE II - PAYOFF PHASE
 6. Glyceraldehyde-3-Phosphate Dehydrogenase
(GAPDH) first "High-energy" intermediate
formation.
 7. Phosphoglycerate Kinase (PGK): First ATP
Generation.
 8. Phosphoglycerate Mutase (PGM).
 9. Enolase: second "High-energy" intermediate
formation.
 10. Pyruvate Kinase (PK): Second ATP generation.

18. (F) STEP 6 - GLYCERALDEHYDE-3-PHOSPHATE DEHYDROGENASE
(GAPDH): FIRST “HIGH-ENERGY” INTERMEDIATE FORMATION.

19. (G). STEP 7 - PHOSPHOGLYCERATE KINASE (PGK):
FIRST ATP GENERATION

20. (H). Step 8 - Phosphoglycerate Mutase (PGM)

21. (I) STEP 9 - ENOLASE: SECOND “HIGH-
ENERGY” INTERMEDIATE FORMATION.
(DEHYDRATION REACTION)

22. Pyruvate Kinase
Tautomerization of
enolpyruvate to pyruvate.

23. CONCLUSION
Glycolysis is an important source of energy supply for brain,
retina,skinand renal medula.
The crucial significance of glycolysis is ability to generate
ATP in theabsence of oxygen.
Glycolysis is the break down of glucose which is the only
source that supplies energy to the skeletal muscle, under
anaerobic conditions.

24. REFERENCE
U. Satyanarayana
U. Chakrapani
Biochemistry- J L Jain, Sunjay Jain,NitinJain
Krishna’s Zoology
Wikipedia