Complete Set of Metabolism of Carbohydrate in that second chapter, glycolysis. This presentation covers complete glycolysis pathway with step wise animated reactions and it includes clinical aspects also. This presentation is good for MBBS students.

1. Ashok Katta

2. Other name Embden-Meyerhof
Pathway (E.M. Pathway).
The sequence of reactions converting
glucose to pyruvate or lactate, with
the production of ATP.

3. Major pathway for utilization of glucose.
Takes place in all cells of the body.
The enzymes of this pathway are
present in cytosol of the cell.
Occurs both in aerobic & anaerobic
conditions.
Major pathway for ATP in tissues lacking
mitochondria, e.g. RBCs,lens,cornea, etc
Very essential for Brain.

4. The breakdown of glucose to 2 molecules
of pyruvate is drought about by sequence
of 10 reactions which can be divided into
Energy investment phase
Energy generation phase.
Reactions of Glycolysis
Glucose 2 pyruvate+7ADP 7Pi+ 7ATP+ +2H2O

5. Glucose is get activated by phosphorylation to glucose 6-
phosphate by Hexokinase or Glucokinase.
This is irreversible reaction.
Requires energy (ATP) and Mg++.
Hexokinase is present in all tissues, has low Km for
substrate. And is inhibited by Glucose 6-Phosphate.
Glucokinase present in liver, has high Km for glucose.
And is not inhibited by Glucose 6-Phosphate.
Glucose 6-Phosphate is impermeable to cell membrane,
so, glucose is trap within the cell & is further utilized for
energy purpose.
O H
OH
OHH
HO
H
CH2OH
OH
H
H
Glucose
ATP ADP
Glucose 6-phosphate
1 Hexokinase/
Glucokinase
O H
OH
OHH
HO
H
OH2C
OH
H
H
P
Mg++

6.  Glucose 6-Phosphate is isomerised to fructose 6-
phosphate by an isomerase.
 This is reversible reaction.
2
O CH2OH
OH
OH
H HO
H
H
OH2CP
Glucose 6-phosphate
O H
OH
OHH
HO
H
OH2C
OH
H
H
P
Fructose 6- phosphate
Phosphohexose
isomerase

7. fructose 6-phosphate is phosphorylated to
fructose 1,6-bisphosphate by the enzyme
phosphofructokinase (PFK).
Energy for this reaction is derived from ATP.
PFK is important key enzyme of this pathway.
This is irreversible reaction.
O CH2OH
OH
OH
H HO
H
H
OH2CP
Fructose 6- phosphate Fructose 1,6- bisphosphate
O CH2O
OH
OH
H HO
H
H
OH2C P
P
ATP ADP
Phosphofructo
kinase

8. Fructose 1,6-bisphosphate is splits into two
molecules.
Glyceraldehyde 3-phosphate
Dihydroxyacetone phosphate
The enzyme is Aldolase.
This is reversible reaction.
Fructose 1,6- bisphosphate
O CH2O
OH
OH
H HO
H
H
OH2C PP
Aldolase
CH2O-
C = O
CH2OH
P
HCOH
CH2O-
HC=O
P
Glyceraldehyde
3-phosphate
Dihydroxyacetone
phosphate

9. Dihydroxyacetone phosphate is isomerised to
glyceraldehyde 3-phosphate by the enzyme
Phosphotriose isomerase.
In this reaction, 2 molecules of glyceraldehyde
3-phosphate are formed.
Glyceraldehyde 3-phosphate can also be
synthesized from glycerol (fats) by
phosphorylation.
This is reversible reaction.
CH2O-
C = O
CH2OH
P
HCOH
CH2O-
HC=O
P
Glyceraldehyde
3-phosphate
Dihydroxyacetone
phosphate
Phosphotriose
isomerase

10. Glyceraldehyde 3-phosphate is gets
dehydrogenated and phosphorylated to 1,3-
bisphosphoglycerate (1,3-BPG) by G3-P DH.
Reducing equivalents are carried by NAD+.
This is reversible reaction.
H C OH
CH2O-
HC=O
P
Glyceraldehyde
3-phosphate
=
H C OH
CH2O-
C- O-
O
P
P
1,3-Bisphosphoglycerate
G3-P
Dehydrogenase
2 NAD+
+2 P 2 NADH+2H
6

11. The energy of 1,3-bisphosphoglycerate (1,3-
BPG) is used for synthesis of ATP in this reaction.
This is example of substrate level
phosphorylation.
here energy is trapped directly from substrate
(1,3BPG) without involvement of ETC.
This is reversible reaction.
Arsenate inhibit this reaction.
=
HCOH
C-O-
CH2O-
O
P
P
1,3-Bisphosphoglycerate
HCOH
COOH
CH2O- P
2ATP2ADP
7 3-Phosphoglycerate
kinase
3-Phosphoglycerate

12. Phosphoglycerate mutase converts 3-
Phosphoglycerate to 2-Phosphoglycerate by
shifting the phosphate gr.
This is readily reversible reaction.
HCOH
COOH
CH2O- P
3-Phosphoglycerate
HCO-
COOH
CH2OH
P
2-Phosphoglycerate
8 Phosphoglycerate
mutase

13. 2-Phosphoglycerate is converted into
Phosphoenol pyruvate by the enzyme enolase by
removing one water molecule.
The reaction is reversible.
Enolase requires Mg++ for there action.
Fluoride irreversibly inhibit enolase there by
stops the whole glycolysis.
Therefore, fluoride is added to blood during
estimation of blood sugar.
HCO-
COOH
CH2OH
P
2-Phosphoglycerate
C-O-
COOH
CH2
=
P
Phosphoenol pyruvate
9
Enolase
H2O
Mg++

14. Phosphoenol pyruvate converts into pyruvate
by the enzyme pyruvate kinase.
Here also energy of PEP is trapped into ATP.
This is example of substrate level
phosphorylation.
pyruvate kinase is key glycolytic enzyme.
The reaction is irreversible.
C-O-
COOH
CH2
=
P
Phosphoenol
pyruvate
C O
COOH
CH3
=
pyruvate
10 Pyruvate kinase
2ATP
2ADP

15. In anaerobic condition, pyruvate is
reduced lactate by the enzyme lactate
dehydrogenase (LDH).
Here reducing equivalents (NADH+H+)
is used which are synthsized in 5th step
of glycolysis.
C O
COOH
CH3
=
pyruvate
C-OH
COOH
CH3
LactateNAD+
NADH+2H+
Lactate
dehydrogenase

16. O H
OH
OHH
HO
H
CH2OH
OH
H
H Glucose
ATP
ADP
4
Glucose 6-
phosphate
Fructose 6-
phosphate
Fructose 1,6-
bisphosphate
1
2
3
Hexokinase/
Glucokinase
Phosphohexose
isomerase
Phosphofructo
kinase
Aldolase
O H
OH
OHH
HO
H
OH2C
OH
H
H
P
O CH2OH
OH
OH
H HO
H
H
OH2CP
O CH2O
OH
OH
H HO
H
H
OH2C PP
ATP
ADP

17. CH2O-
C = O
CH2OH
P
HCOH
CH2O-
HC=O
P
HCOH
COOH
CH2O- P
HCO-
COOH
CH2OH
P
C-O-
COOH
CH2
=
P
=
HCOH
C-O-
CH2O-
O
P
P
C O
COOH
CH3
=
2 ATP
C O
COOH
CH3
=
Glyceraldehyde
3-phosphate
Dihydroxyacetone
phosphate
1,3-Bisphosphoglycerate
3-Phosphoglycerate
2-Phosphoglycerate
Phosphoenol-
pyruvate
pyruvate Lactate
2 NAD+
+2 P
2 NADH+2H
2ADP
2 ATP
2ADP
5
6
7
8
9
10
Isomerase
G3-P
Dehydrogenase
3-Phosphoglycerate
kinase
Phosphoglycerate
mutase
Enolase
Pyruvate kinase LDH
2 NADH
+2H +
2 NAD+

18. Regulation of Glycolysis
Glycolysis is regulated by activating or
inhibiting following key glycolytic
enzymes…
Glucokinase and hexokinase
Phosphofructokinase
Pyruvate kinase
Insulin favours glycolysis by activating
these enzymes
Glucagon, glucocorticoid inhibits
glycolysis.

19. Hexokinase and Glucokinase
Hexokinase is inhibited by glucose 6-
phosphate
Inhibition of PFK indirectly inhibits
hexokinase activity.
Glucokinase in the liver is not inhibited
by G6P.
It has high Km (low affinity) for
glucose. Hence, it can act only when
there is plenty of glucose.

20. Phoshofructokinase (PFK)
It is most important rate-limiting
enzymes.
PFK is allosterically regulated enzyme.
ATP, Citrate are allosteric inhibitors.
Low PH has inhibitory effect on PFK.
AMP, ADP, F 6-P increase the activity of
PFK
Fructose2,6-bisphoshate (F2,6BP) is
increase the activity of PFK.
F26BP is formed from F6P by enzyme
PFK-2

21. Pyruvate Kinase (PK)
It is most important regulatory enzyme
of glycolysis.
The enzyme has L & M isoenzymes,
both forms are inhibited by ATP.
So, when ever energy is plenty in the
cell, glycolysis is inhibited.
F1,6-BP activate pyruvate kinase.
The enzyme is also regulated by
covalent modification.
Insulin increases its activity where as
glucagon inhibits.

22. Summary of regulation of Glycolysis
Glucose
Glucose 6-phosphate
Fructose 6- phosphate
Fructose 1,6- bisphosphate
Glyceraldehyde 3-pDihydroxyacetone p
1,3-Bisphosphoglycerate
3-Phosphoglycerate
2-Phosphoglycerate
Phosphoenol pyruvate
pyruvate
Citrate
+
-
ATP
ATP
+
ADP
ADP
+
2,3-Bisphosphoglycerate
-
Insulin
Glucocorticoid
-

23. Energetic of Glycolysis
 Energy yield (ATP)/glucose in
glycolysis under aerobic
condition.
 Reaction no.1(Hexokinase) -1ATP
 Rea. 3 (PFK) -1ATP
 Rea. 6 (G 3-PDH) +2.5x2=5
 Rea. 7 (BPGK) + 1x2=2
 Rea. 10 (PK) + 1x2=2
Total=9-2=7ATP
 Energy yield (ATP)/glucose in
glycolysis under anaerobic
condition.
 Rea. no.1(Hexokinase) -1ATP
 Rea. 3 (PFK) -1ATP
 Rea. 7 (BPGK) + 1x2=2ATP
 Rea. 10 (PK) + 1x2=2ATP
Total=4-2=2ATP

24. Formation of 2,3 bisphoshoglycerate
(Rapaport-Leubering Cycle)
HCOH
COOH
CH2O- P
=
HCOH
C-O-
CH2O-
O
P
P
2 ATP
1,3-Bisphosphoglycerate
3-Phosphoglycerate
2ADP
=
HC-O-
C-O-
CH2O-
O
P
P
2,3-Bisphosphoglycerate
BISPHOSPHOGLYCERATE
MUTASE
2,3-BISPHOSPHOGLYCERATE
PHOSPHATASE
Pi
3-Phosphoglycerate
kinase

25. HCOH
COOH
CH2O- P
=
HCOH
C-O-
CH2O-
O
P
P
2ATP
1,3-Bisphosphoglycerate
3-Phosphoglycerate
2ADP
=
HC-O-
C-O-
CH2O-
O
P
P
2,3-Bisphosphoglycerate
BISPHOSPHOGLYCERATE
MUTASE
2,3-BISPHOSPHOGLYCERATE
PHOSPHATASE
Pi

26. Disorders of Glycolysis
Pyruvate Kinase Deficiency-
Genetic deficiency of PK in RBCs leads to hemolytic
anemia.
Hexokinase Deficiency-
Genetic deficiency of PK in RBCs leads to hemolytic
anemia.

27. Lactic acidosis-
It is the accumulation of lactic acid in the blood.
Normal blood lactate levels are less than 1.2 mM but in
lactic acidosis, level may be 15 mM or more.
The high conc of lactate results in lowered blood pH (7.2)
and bicarbonate levels.
This may be results from,
Excessive NADH production, eg-ethanol intoxication.
Impaired pyruvate dehydrogenase activity, eg-thiamine deficiency
Inhibition of lactate utilization for gluconeogenesis, eg –
hereditary fructose intolerance.
Anoxia due to collapse of the circulatory system, eg- MI, Shock
Clinical Significance of blood lactate
Measurement of blood lactate is useful to assess the presence and
severity of shock & to monitor the patients recovery.
In many disorders, levels of blood lactate provide rapid & early
detection of oxygen dept in patient.

28. Metabolic Fate of Pyruvate
Pyruvate
Acetyl coA
Lactate
Alanine
Oxalo acetate
Glucose
MalateAspartate

29. Thank you