This document summarizes glycolysis, the pathway that breaks down glucose to pyruvate. It describes glycolysis as occurring in three phases: an energy investment phase where ATP is used to phosphorylate glucose, a splitting phase where a six-carbon molecule splits into two three-carbon molecules, and an energy generation phase where ATP is regenerated. Glycolysis produces a net of two ATP per glucose under aerobic conditions and two ATP under anaerobic conditions. Key enzymes in the pathway include hexokinase, phosphofructokinase, aldolase, and pyruvate kinase.

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Glycolysis-Pathway –
-Glycolysis is derived from the Greek words (glycose—
Sweet or Sugar; lysis—Dissolution).
-It is also called as “EMBDEN- MEYERHOF
PATHWAY[EMP]”.
-It is degradation of glucose to generate ATP and to
provide intermediates for other synthetic and
metabolic pathways. Aerobically it ends with pyruvate
while anaerobically lactate is the end product.
-The oxidation of glucose to pyruvate and lactate.
-Glycolysis is defined as the sequence of reactions
converting glucose (or glycogen) to pyruvate or lactate,
with the production of ATP.
-The enzyme fructose bisphosphate aldolase is one of
the most critical steps in the pathway.
C a r b o h y d r a t e
m e t a b o l i s m :

2. Reactions of glycolysis:
The sequence of reactions of glycolysis is given in the
pathway can be divided into three distinct phases.
[A] . Energy investment phase or priming stage
[B] . Splitting phase
[C] . Energy generation phase.
[A] .Energy Investment Phase or Priming Stage
-
01.Glucose is phosphorylated to glucose 6-
phosphate by hexokinase or glucokinase
This is an irreversible reaction, dependent on ATP
and Mg2+.
Glucose 6-phosphate is impermeable to the cell
membrane.
02.Glucose 6-phosphate undergoes isomerization
to give fructose 6-phosphate in the presence of
the enzyme phosphohexose isomerase and Mg2+.
03. Fructose 6-phosphate is phosphorylated to
fructose 1,6-bisphosphate by
phosphofructokinase (PFK). This is an irreversible
and a regulatory step in glycolysis.

3. [B]. Splitting Phase –
04. The six-carbon fructose
1,6bisphosphate is split (hence the name
glycolysis) to two three-carbon
compounds, glyceraldehyde 3-phosphate
and dihydroxyacetone phosphate by the
enzyme aldolase (fructose
1,6bisphosphate aldolase).
05. The enzyme trio -Phosphate isomerase
catalysis the reversible interconversion of
glyceraldehyde 3-phosphate and
dihydroxyacetone phosphate. Thus, two
molecules of glyceraldehyde 3-phosphate
are obtained from one molecule of
glucose.

4. [C] . Energy Generation Phase.
[06]. Glyceraldehyde -3-phosphate dehydrogenase
[GAPDH] dehydrogenates and adds an inorganic
phosphate to glyceraldehyde 3-phosphate , producing
1,3-bisphosphoglycerate.
[07]. Phosphoglycerate kinase transfer a phosphate
group from 1,3-bisphophoglycerate to ADP to form ATP
and 3-phosphoglycerate.
[08]. The enzymee phosphoglycerol mutase relocates
the P from 3-phosphoglycerate from the 3rd carbon to
the 2nd carbon to form 2-phosphoglycerate.
[09]. The enzyme enolase removes a molecule of water
from 2-phosphoglycerate to form phosphoenolpyruvic
acid (PEP).
[10]. The enzyme pyruvate kinase transfer a P from
phosphoenolpyruvate (PEP) to from pyruvic acid and
ATP result in step 10.
- Step 1 & 3 = -2ATP.
- Srep 7 & 10 = -4ATP.
- Net “visible” ATP produced = 2

6. Energetics of Glycolysis =
Energy yield [ATP] glucose
in glycolysis under aerobic
condition.
Energy yield [ATP] glucose
in glycolysis under
anaerobic condition.
Reaction number 1st
( hexokinase) -1ATP.
Reaction number 1st
( hexokinase) -1ATP.
Reaction number 3[PFK] -
1ATP
Reaction number 3[PFK] -
1ATP
Reaction number 6 (G 3-
PDH) + 2.5*2= 5
Reaction number 7 (PFK)
+1*2 = 2ATP
Reaction number 7 [ BPGK ]
+ 1*2 =2
Reaction number 10[PK]
+1*2 = 2ATP
Reaction number 10[PK] +
1*2 = 2
Total =
9-2 = 7ATP.
Total = 4-2 =2ATP.

7. Rahul Pal’s
GLYCOLYSIS PATHWAYS