Glycolysis (from glycose, an older term for glucose + -lysis degradation) is the metabolic pathway that converts glucose C6H12O6, into pyruvate, CH3COCOO− + H+. The free energy released in this process is used to form the high-energy molecules ATP (adenosine triphosphate) and NADH (reduced nicotinamide adenine ...

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GYCOLYSIS
Mr. RAJENDRA SINGH Jr.
Biotechnology Network

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Synopsis: -
1. Introduction
2. History
3. Carbohydrate Metabolism
4. Biological significance.
5.References

3. 1. GLYCOLYSIS
INTRODUCTION:
* Glycolysis is derived from greek word (glycose-
glucose, lysis-breakdown).
* During this process one molecules of glucose is
degraded into two molecules of pyruvate.
* Free energy is released in this process and is stored as
two molecules of “ATP” and two molecules of NADH.
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4. 2. HISTORY:
•Glycolysis was the very 1st biochemistry studied and it is the 1st metabolic
pathway discovered.
•Louis pasture(1854-1864): observed that fermentation is caused by micro-
organisms and also found that aerobic growth requires less glucose than
anaerobic condition.
•Buchner(1897): found that reaction of glycolysis can be carried out in a cell-free
yeast extract.
•Harden and young(1905): found that (1). Inorganic phosphate is required
fermentation.
(2). Yeast extract could be separated in
small molecular weight essential coenzymes and bigger molecules called zymase.
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• There is 60% of ingested food consist of polysaccharide carbohydrates,
while the disaccharide carbohydrates like sucrose and lactose are important
in the diet of infants.
• The end product of carbohydrate digestion is mainly glucose, fructose and
galactose.
• These simple sugars are absorbed in the intestine and are carried to the liver
through the blood stream. Here they are transferred into glycogen through
glucose-6-phosphate.
• The glycogen is stored in the liver.
• The carbohydrate metabolism or digestion of carbohydrate is takes by two
steps:
1. Catabolism
2. Anabolism

6. 1. Catabolism:
* In catabolism degradation of complex
organic molecules into simpler molecules.
* In this process energy is released.
2. Anabolism:
* Anabolism is the process of biosynthesis in
which complex molecules are produced from simpler
molecules.
* In this process energy is required.
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7. Glycolysis: ( Embden-meyerhof-parnas method/pathway)
* Glycolysis is the breakdown of glucose upto the formation of
pyruvic acid. Each glucose molecules forms two molecules of pyruvic acid.
* The breakdown of glucose is takes place in a series of steps, each
stepwise reaction is catalyzed by a specific enzyme.
* Glycolysis may be divided into two phases :
1. Preparatory phase.
2. Oxidative phase.
1. Preparatory phase :-
* The 1st four (1-4) steps in glycolysis represents the
preparatory phase.
* In this phase breakdown of glucose and low energy
phosphorylation occurs and I is expended.
2. Oxidative phase :-
* The end (5-9) steps in glycolysis represents the
oxidative phase.
* In this phase high-energy phosphate bonds are
formed and the energy is stored.
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8. GLUCOSE
GLUCOSE-6-PHOSPHATE
FRUCTOSE-6-PHOSPHATE
FRUCTOSE-1-6-DIPHOSPHATE
DIHYDROXIACETONE
PHOSPHATE (DHAP)
PHOSPHOGLYCERALDEH
YDE
ATP
ADP
ATP
ADP
ISOMERISATI
ON
1. PHOSPHORYLATION
( HEXOKINASE )
2. ISOMERISATION
(
PHOSPHOGLUCOISOMERASE )
3. SECOND PHOSPHORILATION
( PHOSPHOFRUCTOKINASE )
4. CLEAVAGE
( ALDOLASE )
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9. PHOSPHOGLYCERALDEHYDE
( PGAL )
1, 3 – DIPHOSPHOGLYCERIC ACID
3 – PHOSPHOGLYCERIC ACID
2 – PHOSPHOGLYCERIC ACID
PHOSPHOENOL PYRUVIC ACID
H2PO4 2H
NAD
NADH+H
P
ADP
ATP
H2O
ADP
ATP
5. PHOSPHORYLATION
AND
OXIDATTIVE DEHYDROGENATION
(PHOSPHOTRIOSE
DEHYDROGENATION)
6. ATP GENERATION
( PHOSPHOGLYCERYLKINASE )
7. ISOMERISATION
( PHOSPHOGLYCEROMUTASE )
8. DEHYDRATION
( ENOLASE )
9. ATP GENERATION
( PYRUVATE KINASE ) 9

10. PYRUVIC ACID
LACTIC ACID ACETALDEHYD
E
Krebs cycle
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11. Steps involved in Glycolysis :-
• It is the first step in the breakdown of carbohydrates.
• The glucose is stable compound so, it normally resist the
breakdown.
• The activation of glucose molecule takes place by a
reaction called oxidative phosphorylation.
• A phosphate group is attached to glucose by a low energy
phosphate bond ( -p ), and glucose-6-phosphate is formed.
• The reaction is facilitated by an enzyme called
Hexokinase with mg2+ as an activator.
• The phosphate group is derived from ATP which
breakdown to ADP.
example:-
* The hormones insulin and estrogen
promote phosphorylation of blood glucose to glucose-6-
phosphate.
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12. 2. ISOMERISATION:-
• Glucose-6-phosphate undergoes internal molecular
rearrangement to form Fructose-6-phosphate.
• The catalytic enzyme is Phosphoglucoisomerase.
• No changes takes place in the low energy value of the
phosphate bond.
3. SECOND PHOSPHORYLATION :-
• Fructose-6-phosphate undergoes phosphorylation to
form fructose-1,6-diphosphate.
• The catalytic enzyme is phosphofructokinase.
• The phosphate group is derived from ATP which
breaks down to ADP.
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13. 4. CLEAVAGE:-
• Fructose-1,6-diphosphate splits into two halves between
carbon atom 3 and 4 under the action of enzyme Aldolase.
• The two halves phosphates, each contain three carbon
atoms, but are not identical.
• The one half is dihyroxyacetone phosphate (DHAP )
and the other is 3-phosphoglyceraldehyde.
• These molecules undergoes isomerization and become
identical 3-phosphoglyceraldehyde (PGAL ) molecules.
• The catalyzing enzyme is Triosephosphate isomerase.
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14. 5. PHOSPHORYLATION AND OXIDATIVE DEHYDROGENATION :-
• The phosphoglyceraldehyde ( PGAL ) undergoes
simultaneous phosphorylation and oxidative dehydrogenation.
• The PGAL molecule has a phosphate group attached to the
one end by a low energy bond ( -p ).
• During phosphorylation, under the catalyzing action of
enzyme phosphotriose dehydrogenase, a second phosphate
group is added to the other end.
• The phosphorylating agent which provides the phosphate
group is phosphoric acid.
• Oxidative dehydrogenation takes place simultaneously. Two
atoms of hydrogen are removed and are accepted by NAD+
(nicotinamide adenine dinucleotide), which is converted into
NADH+H+ .
• The newly added phosphate group acquires a high energy
phosphate bond ( ~ P ). The end product is 1, 3-
diphosphoglyceric acid, an energy rich compound is formed. .

15. 6. ATP GENERATION :-
• 1, 3-diphosphoglyceric acid now transfer its phosphate with
high energy bond to ADP, 3-phosphoglyceric acid ( PGAL ).
• The catalytic enzyme is phosphoglyceryl kinase.
• ADP acquires the high energy bond phosphate and becomes
ATP,
7. ISOMERIZATION :-
• The 3-phosphoglyceric acid molecules undergoes internal
rearrangement and becomes 2-phosphoglyceric acid.
• The catalyzing enzyme is phosphoglyceromutase.
8. DEHYDRATION:-
• The 2-phosphoglyceric acid molecules loses hydrogen and
oxygen in the form of water ( dehydration ), to form phosphoenol
pyruvic acid.
• The step is catalyzed by an enzyme Enolase.

16. 9. ATP GENERATION :-
• The phosphoenol pyruvic acid molecules transfers its
high energy phosphate bond to ADP, which is converted
into ATP, and pyruvic
acid is formed.
• The reaction is catalyzed by an enzyme called Pyruvate
kinase.
• It should be noted that two molecules of pyruvic acid are
formed per molecules of glucose metabolished.
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4. BIOLOGICAL SIGNIFICANCE:-
* In the absence of oxygen pyruvic acid is converted into either
ethyl alcohol or lactic acid.
* Pyruvic and lactic acids may be returned to the liver where they
can be resynthesized to form glucose or glycogen by reverse
anaerobic glycolysis.
* Lactic and pyruvic acids may also be broken down in the liver
to yield carbon dioxide and water through kreb’s cycle .

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5. References:-
I. Lehninger’s Principle of Biochemistry (5th) Edition - David L.
Nelson & Michael M. Cox.
II. Fundamentals of Biochemistry – J.L.JAIN 2005 S. CHAND &
COMPANY LTD. RAM NAGAR, NEW DELHI-110 055
III. https://en.wikipedia.org/wiki/Glycolysis

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Prepared by :
KIRAN KUMAR H
SHWETA TIWARI
RAJENDER SINGH