Glycolysis

Glycolysis (from glycose, an older term for glucose + -lysis degradation) is the metabolic pathway that converts glucose C6H12O6, into pyruvate, CH3COCOO− + H+.

1. GLYCOLYSIS
MSD

2. Definition
Derived from Greek word
Glykys= Sweet
Lysis= splitting
The process in cell metabolism by which
carbohydrates and sugars, especially
glucose, are broken down, producing (C
6H
12O
6)
ATP and pyruvic acid and two "high
energy" electron carrying molecules
of NADH.
Glucose = (C
6H
12O
6)

3. Glycolysis
•Glycolysis isthe stepwise degradation of glucose (and other simple
sugars).
•Glycolysis is a paradigm of metabolic pathways.
•Carried out in the cytosol of cells, it is unique, in that it can function
either aerobically or anaerobically, depending on the availability of
oxygen and the electron transport chain.
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4. Overview of Glycolysis
•Glycolysis consists of two phases-
•In the first, a series of five reactions, glucose is broken down to two
molecules of glyceraldehyde-3-phosphate.
•In the second phase, five subsequent reactions convert these two
molecules of glyceraldehyde-3-phosphate into two molecules of
pyruvate.
•Phase 1 consumes two molecules of ATP.
•The later stages of glycolysis result in the production of four molecules
of ATP.
•The net is 4 –2 = 2 molecules of ATP produced per molecule of glucose.
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5. Overview of Glycolysis
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o
Most of the details of
this pathway (the first
metabolic pathway to
be elucidated) were
worked out in the first
half of the 20th century
by the German
biochemists Otto
Warburg, G. Embden,
and O. Meyerhof.
o
In fact, the sequence
of reactions in is often
referred to as the
Embden-Meyerhof
pathway.

6. Steps of Glycolysis
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7. 10 Steps involves in Glycolysis

8. Step 1
•The enzyme hexokinasephosphorylates(adds a phosphate
group to)glucose in the cell's cytoplasm.

9. Step 2
•The enzyme phosphoglucoisomeraseconverts glucose 6-
phosphate into its isomer fructose 6-phosphate.

10. Step 3
•The enzyme phosphofructokinaseuses another ATP molecule
to transfer a phosphate group to fructose 6-phosphate to
form fructose 1, 6-bisphosphate.

11. Step 4
•The enzyme aldolasesplits fructose 1, 6-bisphosphate into
two sugars that are isomers of each other. These two sugars
are dihydroxyacetonephosphate and glyceraldehyde
phosphate.

12. Step 5
•The enzyme triosephosphate isomeraserapidly inter-
converts the molecules dihydroxyacetonephosphate and
glyceraldehydephosphate.
•Glyceraldehydephosphate is removed / used in next step of
Glycolysis.

13. •Net result for steps 4 and 5:
Fructose 1, 6-bisphosphate↔ 2 molecules of Glyceraldehyde
phosphate (C
3H
5O
3P
1)

14. Step 6
•enzyme triosephosphate dehydrogenase
•enzyme transfers a hydrogen (H
-
) from glyceraldehydephosphate to (NAD
+
) to
form NADH.
Triosephosphate dehydrogenase+ 2 H
-
+ 2 NAD
+
→ 2 NADH + 2 H
+
•Next triosephosphate dehydrogenaseadds a phosphate (P) from the cytosolto
the oxidized glyceraldehydephosphate to form
1, 3-bisphosphoglycerate.
TPD+ 2P + 2 glyceraldehydephosphate → 2 molecules of 1,3-bisphosphoglycerate

15. Step 7
•The enzyme phosphoglycerokinasetransfers a P from
1,3-bisphosphoglycerate to a molecule of ADP to form ATP
•This happen for each molecule of 1,3-biphosphoglycerate
Result in step 6: 2 molecules of 3-phosphoglycerate (C
3H
5O
4P
1) + 2 ATP

16. Step 8
•The enzyme phosphoglyceromutaserelocates the P from 3-phosphoglycerate
from the 3rd carbon to the 2nd carbon to form
2-phosphoglycerate.
2 molecules of 2-Phosphoglycerate (C
3H
5O
4P
1)

17. Step 9
•The enzyme enolaseremoves a molecule of water from 2-
phosphoglycerate to form phosphoenolpyruvicacid (PEP).
Result: 2 molecules of C
3H
3O
3P
1

18. Step 10
•The enzyme pyruvatekinasetransfers a P from PEP to ADP to
form pyruvicacid and ATP
Result in step 10: 2 molecules of 2 ATP + 2NADH

19. Net energyATP utilizedATP produced
2 ATP2ATP
From glucose to
glucose -6-p.
From fructose -6-p
to fructose 1,6 p.
4 ATP
(Substrate level
phosphorylation)
2ATP from 1,3 DPG.
2ATP from
phosphoenol
pyruvate
In absence of oxygen
(anaerobic
glycolysis)
6 ATP
Or
8 ATP
2ATP
-From glucose to
glucose -6-p.
From fructose -6-p
to fructose 1,6 p.
4 ATP
(substrate level
phosphorylation)
2ATP from 1,3 BPG.
2ATP from
phosphoenol
pyruvate.
In presence of
oxygen (aerobic
glycolysis)
+ 4ATP or 6ATP
(from oxidation of 2
NADH + H in
mitochondria).
Energy Production of Glycolysis

20. Substrates produced by different reaction can enter glycolysis at different
points. Eg. When an animal breakdown glycogen glucose 6 phosphate is
produced, it can enter at second step. This means one less ATP is required for
the pathway.

21. Inhibitors of Glycolysis
a)Arsenate and Iodoacetate-Inhibitors of Glyceraldehyde-3-P
dehydrogenase
b)Bromo hydroxy acetone phosphate-Inhibitor of dihydroxy acetone
phosphate
c)Fluoride-Inhibitor of Enolase
d)Oxamate-Inhibitor of Lactate dehydrogenase
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