Basic Glycolysis pathway

1. BIOCHEMISTRY- III
CATABOLIC PATHWAYS OF
CARBOHYDRATES - GLYCOLYSIS
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2. Biosynthetic pathways
1. Biosynthesis of Carbohydrates
2. Biosynthesis of Lipids
Biosynthesis of Fatty acids
Biosynthesis of Membrane Lipids
3. Biosynthesis of Amino acids
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3. Glycolysis takes place in the Cytosol of cells.
Glucose enters the Glycolysis pathway by conversion to glucose-6-
phosphate.
Initially there is energy input corresponding to cleavage of two ~P
bonds of ATP.
H O
OH
H
OHH
OH
CH2OPO3
2
H
OH
H
1
6
5
4
3 2
glucose-6-phosphate
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5. Glycolysis
Glucose is converted to two molecules of pyruvate.
An anaerobic reaction in cytoplasm.
10 Reactions
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6. A. Energy investment phase or Preparative or priming
stage
B. Splitting phase
C. Energy generation phase or Pay-off phase
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7. Glycolysis
Steps [1] – [3] and [4] energy investment phase and splitting phase:
The 6-carbon glucose molecule is converted into two 3-carbon segments.
2 ATP molecules are hydrolyzed.
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8. Glycolysis
Steps ]- [5] and [6] – [10] Splitting and energy-generating phase:
producing 1 NADH and 2 ATPs for each pyruvate formed.
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9. Glycolysis
Enzymes:
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10. Step [1] begins with the
phosphorylation of glucose
into glucose 6-phosphate,
using an ATP and a kinase
enzyme.
Glycolysis
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11. Step [2] isomerizes
glucose 6-phosphate to
fructose 6-phosphate
with an isomerase enzyme.
Glycolysis
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12. Step [3] is the
phosphorylation of
fructose 6-phosphate into
fructose 1,6-bisphosphate
with a kinase enzyme.
Glycolysis
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13. Glycolysis
Overall, the first three steps of glycolysis:
1. 2 phosphate groups is added.
2. A 6-membered glucose ring is isomerized
into a 5-membered fructose ring.
3. The energy stored in 2 ATP molecules is utilized to
modify the structure of glucose
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14. Glycolysis- Splitting phase
Step [4] cleaves the fructose ring into a dihydroxy-acetone phosphate
and a glyceraldehyde 3-phosphate.
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15. Step [5] isomerizes the dihydroxyacetone phosphate
into another glyceraldehyde 3-phosphate.
Glycolysis
Thus, the first phase of glycolysis converts glucose into
2 glyceraldehyde 3-phosphate units and 2 ATP is used.
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16. In step [6] the aldehyde end of the molecule is oxidized and
phosphorylated by a dehydrogenase enzyme and NAD+;
this produces 1,3-bisphospho-glycerate and NADH.
Glycolysis- Energy Generating Phase
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17. Glycolysis
In step [7], the phosphate group is transferred onto an ADP with a
kinase enzyme, forming 3-phosphoglycerate and ATP.
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18. In step [8], the phosphate group is isomerized to
a new position in 2-phosphoglycerate.
Glycolysis
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19. In step [9], water is lost to form phosphoenol-pyruvate.
Glycolysis
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20. Glycolysis
In step [10], the phosphate is transferred to an ADP,
yielding pyruvate and ATP with a kinase enzyme.
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Pyruvate

21. The 2 glyceraldehydes 3-phosphate units are converted into 2
pyruvate units in phase two of glycolysis.
Overall, the energy-generating phase forms 2 NADHs and 4
ATPs.
Glycolysis
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22. Glycolysis
Overall of glycolysis
2 ATPs are used in phase one of glycolysis, and 4 ATPs are made in
phase two of glycolysis.
The net result is the synthesis of 2 ATPs from glycolysis.
The 2 NADHs formed are made in the cytoplasm and must be
transported to the mitochondria to join the electron transport chain
and make ATP.
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23. under aerobic
conditions
under anaerobic
conditions
in fermentation
by microorganisms
The fate of pyruvate
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24. Aerobic conditions
The NADH formed needs O2 to return to NAD+, so without O2 no additional
pyruvate can be oxidized.
Pyruvate must diffuse across the outer and inner membrane of mitochondria
into the matrix.
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25. Fermentation is the anaerobic conversion of glucose to ethanol and
CO2 by yeast and other microorganisms.
Fermentation
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26. REGULATION OF GLYCOLYSIS
 The three enzymes namely hexokinase (and glucokinase), phosphofructokinase and
pyruvate kinase, catalysing the irreversible reactions regulate glycolysis.
 Hexokinase is inhibited by glucose 6-phosphate. This enzyme prevents the
accumulation of glucose 6-phosphate due to product inhibition.
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Glucose 6-phosphate

27. PHOSPHOFRUCLOKINASE (PFK)
 Phosphofruclokinase (PFK) is the most
important regulatory enzyme in glycolysis.
 This enzyme catalyses the rate limiting
committed step.
 PFK is an allosteric enzyme regulated by
allosteric effectors ATP, citrate and H+ ions
(low pH) are the most important allosteric
inhibitors.
 Whereas, fructose2 ,6-bisphosphate, ADP,
AMP and Pi are the allosteric activators.
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28. ROLE OF FRUCTOSE 2, 6-BISPHOSPHATE
IN GLYCOLYSIS
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29. REGULATION OF PYRUVATE KINASE
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Inhibited by ATP and activated by F1,6-B