Glycolysis or glycolytic pathway ppt/pdf

Glycolysis is a metabolic pathway that breaks down glucose into pyruvate, releasing energy in the form of ATP. It occurs in the cytoplasm of cells and does not require oxygen, making it an anaerobic process. Glycolysis consists of ten enzyme-catalyzed steps, divided into two phases: the investment phase, where ATP is used, and the payoff phase, where ATP and NADH are produced. The end products are two molecules of pyruvate, two ATP (net gain), and two NADH. This process is essential for cellular respiration and provides energy for various biological activities.

1. Definition

* Glycolysis is derived from Greek word GLYKYS which means SWEET and LYSIS
which means SPLITTING. It is universal catabolic pathway of living cells.

* It can be defined as sequence of reactions for breakdown of GLUCOSE to

PYRUVIC ACID ;under aerobic conditions or under anaerobic conditions ; or
Lactate under a

aerobic conditions along the production of small amount of energy

*“The pathway for glycolysis described by Embeden,Mayerhof and Parnas. Hence ‚it
is called EMBEDEN MAYERHOF PATHWAY or EM PATHWAY

«Site of Glycolysis: Glycplysis occurs in cytoplasm of virtually all the cells of body.

2. Types of Glycolysis

“Aerobic Glycolysis: It occurs when oxygen is plentiful. Final product is PYRUVATE
along with production of eight ATP molecules.

*Anerobic Glycolysis: It occurs when oxygen is scarce.Final product is LACTATE along
with production of two ATP molecules

«Steps of Glycolysis: Glucose is converted to pyruvate in 10 steps by glycolysis.
„Glycolytic pathway can be divided into two phases:
1. Preparatory Phase: Glucose extraction phase.

| 2. Payoff Phase: Energy extraction phase.

3. Preparatory phase: The phase is also called Glucose extraction phase. During the

phophorylation of glucose. Its conversion to glyceraldchyde-3-phosphate take place.

Ato,

The steps 1,2,3,4 and 5 are together called prepa

Payoff phase: The phase is also called energy extraction phase. Each step in payoff

5 phase occurs twice per molecule of glucose. The steps after 5 constitute payoff phase. ES

y phase

5. Payoff Phase

E

6. Step1: Uptake and
phospharylation of glucose

Glucose is phospharylated to form

Glucose-6-phosphate

Reaction is catalysed by specific enzy

glucokinase in liver cells and by
nzyme hexokinase in liver
and extrahepatic tissue

speci

s the ATP into ADP, and

Pi is added into glucose.

Glucose

Glucose-6-phosphate

7. Step2: Isomerisation of
Glucose-6-phosphate to
fr uctose-6-phosphate

Glucose-6-phosphate is isomerized to

te by

phosphoglucose isomerase

There is openin,

of glucose »sphate to linear

structure which then changes to
furanose ring se of fructose-6-

phosophate

4
HC-0E] H H
O-CH_-0\_HC-OH E
wy 4 ¡4 I
a H E
OH ae H 0 À, =
H
OH H

8. Step3: Phospharylation of
fructose-6-phosphate to
fructose-1,6-bisphophate.

Fructose-6-phosphate is f
phosohorylated to
fr uctosel ,6-bisphosphate

It catalyses the transfer of pho:

group from ATP to fructose-6-

phosphate

It is irreversible

The enzyme is phosphofructokinose-1.

$ M x 4
<a Eo-< 0 nto
z . RN

9. $ x
Ho _0\ at-0f

Step4: Cleavage of 1, 6-bigy
fructose-1,6-bisphosphate.

1. The six carbon
fructose-1,6-bisphosphate is cleaved ot
into 3 carbon units,onc

| glyceraldehyd
mole

per

2. The enzyme which catalyses reaction

aldolase.

The reaction is reversible.

10. Step5: Interconversion of
triose phosphate.

1. GAP is on direct pathway of
glycolysis;whereas DHAP is not
Hence,Triose phosphate isomerase
| converts DHAP into GAP useful for
ATP. Thus net result is

is now cleaved into 2 molecules

raldehyde-3-phosphate.

on is rapid and reversible

11. Step6: Oxidative
phospharylation of GAP to
1,3-bisphosphate.

1. Itis first step of payoff phase
2. Its catalysed by

| Glyceraldehyde-3-phosphate

dehydrogenase.

Itis energy yielding rea

It is reversible reaction.

12. Step7:conversion of
1,3-bisphosphoglycerate to
3-phosphoglycerate.

1. The enzyme phoshoglycerate kinase
converts 1,3-bisphosphogly
ADP. Forming ATP anc

3-phosphoglycerate.

te to

2. This type of reaction where ATP is
formed at substrate level is call

substrate level phosphoryl:

13. Step8: Conversion of
3-phosphoglycerate to
2-phosphoglycerate.

3-phosphoglycerate i

5 2-phosphoglycerate by shifting

tom,

omerizchie

the enzyme is phosphoogluco mutase.

This is readily reversible reaction

14. Step9: Dehydration of
2-phosphoglycerate to
phosphoenolpyruvate.

1. 2-phosphoglycerate is converted te
phosphoenol pyruvate by enzyme
enolase.

One water molecule is removed

A high cnergy phosphate bond is

produced. The reaction is reversible

15. Step10: Conversion of
phosphoenol pyruvate to
pyruvate.

1. Phosphoenol pyruvate is
dephosphoruled to pyruvate by the
enzyme pyrivate kinase.

One mole of ATP is gene

this reacti

This reaction is again an example of

substrate level phosphorylation

d during

16. Significance of Glycolysis

Glycolysis is the only pathway that is taking place in all the cells of body.

Glycolysis is only source of energy in erythrocytes.

* Glycolytic pathway may be considered as the preliminary step before

complete oxidation.
+ Glyccolytic pathway provides carbon skeleton for synthesis of non essential

amino acids as well a:

crol part of fat.

17. = Thank you EN

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