To understand how the glycolytic pathway is converts glucose to pyruvate. To understand conservation of chemical potential energy in the form of ATP and NADH. To learn the intermediates, enzyme, and cofactors of the glycolytic pathway.

1. GLYCOLYSIS
Presented by
Mr. Amol A. Shirsath

2. CONTENTS:
 Objectives
 Introduction
 Reactions of Glycolytic Pathway
• Stage-1 Reactions
• Stage-2 Reactions
 Summary

3. OBJECTIVES :
• To understand how the glycolytic pathway is converts glucose to
pyruvate.
• To understand conservation of chemical potential energy in the form of
ATP and NADH.
• To learn the intermediates, enzyme, and cofactors of the glycolytic
pathway.

4. INTRODUCTION:
• Glycolysis is a greek word, glycos means sweet and lysis means spilliting.
• Glycolysis is called as universal pathway because it occurs in each and
every cell, as the metabolic enzymes are present in cytosomal fraction of
the cell.
• In glycolysis each glucose molecules splits and converted in to two 3
carbon unit (pyruvate) by sequential reaction.
• During this sequential reactions of Glycolysis , some of the free energy
released from glucose is conserved in the form of ATP and NADH.
• The glycolytic breakdown of glucose is the sole source of metabolic
energy in some mammalian tissues and cell type.
• In anerobic organisms pyruvate is converted to some product like ethanol,
lactic acid by using fermentation.
• Aerobic organisms such as plant and animal, oxidized pyruvate to form
CO2 and H2O .

5. PATHWAY OF GLYCOLYSIS:

6. REACTIONS OF GLYCOLYTIC PATHWAY :
Stage-1 Reactions
Reaction -1. Synthesis of glucose -6-
phosphate.
Reaction -2.Conversion of glucose -6-
phosphate to fructose -6-
phosphate.
Reaction -3. Fructose -6-phosphate to 1,6
diphosphate.
Reaction-4. Fructose -1, 6-bisphosphate to
Dihydroxyacetone phosphate
and glyceraldehydes -3-
phosphate.
Reaction -5. The inter conversion of triose
phosphate.
Stage-2 Reactions
Reaction -6. Oxidation of glyceradehyde
-3 – phosphate.
Reaction -7. Phosphoryl group transfer.
Reaction -8. The interconversion of 3-
phosphoglycerate and 2-
phosphoglycerate.
Reaction -9. Dehydration of 2-
phosphoglycerate.
Reaction -10. Synthesis of pyruvate.

7. Reaction -1. Synthesis of glucose -6-phosphate
• The phosphorylation of glucose in all cell in body is catalyzed by several
enzymes called the hexokinases, ATP is complexed with Mg+2 which is a co-
substrate in this reaction .
• The reaction is essentially irreversible, and glucose is efficiently trapped inside
the cell, as phosphorylated intermediates which do not readily pass through cell
membrane.

8. Reaction - 2.Conversion of glucose -6-phosphate to fructose -6-phosphate
• The reaction is catalyzed by phosphogluco isomarase / phosphohexose
isomarase.
• This enzymatic step prepares the first carom (C-1) for phosphorylation.
• It is freely reversible reaction controlled by substrate-product levels.

9. Reaction -3. Fructose -6-phosphate to 1,6 diphosphate
• The reaction is essentially irreversible.
• In this reaction of Glycolysis phopshofructokinase -1 catalyzes the transfer of
phosphoryl group from ATP to fructose 6-phosphate to yield fructose 1,6- bis
phosphates.
• Phopshofructokinase is the rate limiting enzyme of Glycolysis in most tissues. It
is the major regulatory enzyme of the glycolytic pathway.

10. Reaction -4. Fructose -1, 6-bisphosphate to Dihydroxyacetone phosphate and
glyceraldehydes -3-phosphate
• This reaction completes the first stages of Glycolysis. It is catalyzed by aldose.
• The enzyme fructose 1,6-bisphosphate aldolase, often called simply aldolase,
catalyzes a reversible aldol condensation.
• Fructose -1, 6-bisphosphate is cleaved to yield two different triose phosphates,
glyceraldehydes -3- phosphate and an aldose and Dihydroxyacetone phosphate.

11. Reaction -5. The inter conversion of triose phosphate
• Only one of the two triose phosphates formed by aldolase, glyceraldehydes 3-
Phosphate , can be directly degraded in the subsequent step of Glycolysis .
• The other product DHAP, is rapidly converted to , glyceraldehydes 3- Phosphate
by fifth enzyme triose phosphate isomarase.

12. Reaction -6. Oxidation of glyceradehyde-3 – phosphate
• The reaction catalyzed by Glyceradehyde -3-posphate dehyrogenase , which
requires nicotinamide adenine dinucleotide (NAD+)as an electron carrier. In its
oxidized form NAD+ binds tightly to the enzyme.
• Aldehyde group is dehydrogenated to an acyl phosphate.
• This reaction generates a high energy phosphate bond in 1,3,DPG,which is a
mixed anhydride of phosphoric acid and a carboxylic acid. Because of this , 1,3
–DPG has a high group transfer potential.

13. Reaction -7. Phosphoryl group transfer
• The reaction is catalyzed by phosphoglycerate kinase
• This is the first step in the Glycolysis that generates ATP. It is another of
substrate level phosphorylation.
• The molecular structure of phosphoglycerate kinase is similar to hexokinase
in that it has two lobes (jaws) that each bind one of the substrates (ADP-
Mg2+ or 1,3-bisphosphoglycerate) leading to a large conformational change
in the enzyme that brings the substrates close together and excludes H2O
from the active site.

14. Reaction -8. The interconversion of 3-phosphoglycerate and 2-phosphoglycerate
• The reaction is catalyzed by enzyme phosphoglycerate mutase.
• This reaction is to generate a compound, 2-phosphoglycerate, that is
converted to phosphoenol pyruvate in the next reaction.

15. Reaction-9. Dehydration of 2-phosphoglycerate
• In this Reversible reaction water molecules is removed from phosphoglycerate to
yield phosphoenol pyruvate, which is catalyzed by enzyme enolase.
• However, when enolase converts 2-phosphoglycerate to phosphoenol pyruvate, it
traps the phosphate group in an unstable enol form, resulting in a dramatic
increase in the phosphoryl transfer potential of the triose sugar.

16. Reaction-10. Synthesis of pyruvate
• This last step in glycolysis is catalyzed by enzyme pyruvate kinase .
• In this reaction, the high phosphoryl transfer potential of PEP is used by the
enzyme pyruvate kinase to generate pyruvate, the end product of glycolysis, and 2
ATP are formed for every glucose molecule entering the pathway.
• Pyruvate is a stable compound in cells that is utilized by many other metabolic
pathways.

17. OVERALL BALANCE SHEET - NET GAIN OF ATP
1Glucose + 2 ATP+ 2 NAD+ + 4 ADP + 2 Pi
2 Pyruvate + 2 ADP + 2 NADH + 2 H+ + 4 ATP + 2 H2O
Or
Glucose + 2 NAD+ + 2 ADP + 2 Pi Glucose + 2 NAD+ + 2 ADP + 2 Pi
2 Pyruvate + 2 NADH + 2 H+ + 2 ATP + 2 H2O
• Under aerobic conditions, the two molecules of NADH are reoxidized to NAD+
by transfer of their electrons to the respiratory chain in the mitochondrion.
2NADH + 2H+ + O2 2 NAD+ + 2 H2O

18. • Glycolysis is a near universal pathway by which a glucose molecules is
oxidized to two molecules of pyruvate, with energy conserved as ATP and
NADH.
• The process of Glycolysis is the enzymatic splitting of glucose into two
molecules of pyruvate, and it is the primary sequence in the metabolisms
of glucose by all cell.
• It is an oxidative pathway which does not require oxygen. When it
function in the absence of oxygen the process is referred to as anaerobic
Glycolysis ; when oxygen is available ,as aerobic glycolysis
• The process is catalyzed by 10 cytosolic enzymes and there is a net gain of
two ATPs per molecule of glucose.
• Enzyme limited, regulated steps are catalyzed by hexokinase,
phosphofructokinase-1, and pyruvate kinase.
SUMMARY :