Panel 13–1 Details of the 10 steps of glycolysis
For each step, the part of the molecule that undergoes a change is shadowed in blue,
and the name of the enzyme that catalyzes the reaction is in a yellow box.
CH2OH
Step 1
Glucose is
phosphorylated by ATP to
form a sugar phosphate.
The negative charge of the
phosphate prevents
passage of the sugar
phosphate through the
plasma membrane,
trapping glucose inside
the cell.
CH2O P
O
+
OH
HO
O
hexokinase
ATP
OH
HO
+
OH
+
H+
OH
OH
OH
glucose
glucose 6-phosphate
H
O
Step 2
A readily
reversible
6 CH2O P
rearrangement of
5
the chemical
O
structure
(isomerization)
4
1
moves the
OH
carbonyl oxygen
2
HO
OH
3
from carbon 1 to
carbon 2, forming
OH
a ketose from an
aldose sugar.
(ring form)
(See Panel 2–3,
pp. 70–71.)
ADP
1CH2OH
C1
H
C
OH
HO
C
H
H
C
OH
H
H
C
OH
H
2
3
4
5
phosphoglucose
isomerase
C
O
C
H
C
OH
C
OH
2
HO
CH2O P
6
(open-chain form)
3
4
P OH2C
5
4
5
1
HO
2
3
OH
OH
(ring form)
CH2O P
6
(open-chain form)
glucose 6-phosphate
CH2OH
O
6
fructose 6-phosphate
Step 3
The new hydroxyl
group on carbon 1 is
phosphorylated by ATP, in
preparation for the formation
of two three-carbon sugar
phosphates. The entry of
sugars into glycolysis is
controlled at this step, through
regulation of the enzyme
phosphofructokinase.
P OH2C
CH2OH
O
phosphofructokinase
+
HO
CH2O P
O
ATP
OH
ADP
+
H+
OH
OH
fructose 6-phosphate
fructose 1,6-bisphosphate
CH2O P
P OH2C
+
HO
OH
Step 4
The sixcarbon sugar is
cleaved to produce
two three-carbon
molecules. Only the
glyceraldehyde
3-phosphate can
proceed immediately
through glycolysis.
P OH2C
CH2O P
O
HO
OH
OH
(ring form)
HO
C
O
C
H
H
C
OH
H
C
OH
CH2O P
aldolase
HO
C
O
C
H
H
O
H
C
+
H
C
OH
CH2O P
CH2O P
(open-chain form)
dihydroxyacetone
phosphate
fructose 1,6-bisphosphate
Step 5
The other
product of step 4,
dihydroxyacetone
phosphate, is
isomerized to form
glyceraldehyde
3-phosphate.
CH2OH
C
O
CH2O P
dihydroxyacetone
phosphate
O
H
triose phosphate isomerase
C
H
C
OH
CH2O P
glyceraldehyde
3-phosphate
glyceraldehyde
3-phosphate
Step 6
The two molecules
of glyceraldehyde 3-phosphate
are oxidized. The energygeneration phase of glycolysis
begins, as NADH and a new
high-energy anhydride linkage
to phosphate are formed (see
Figure 13–5).
glyceraldehyde 3-phosphate
dehydrogenase
H
O
C
H
+
C
+
NAD+
O P
O
C
Pi
OH
H
CH2O P
1,3-bisphosphoglycerate
O P
O
The transfer
to ADP of the highenergy phosphate
group that was
generated in step 6
forms ATP.
+
C
C
ADP
OH
H
+
C
CH2O P
CH2O P
3-phosphoglycerate
O–
O
The remaining
phosphate ester linkage in
3-phosphoglycerate,
which has a relatively low
free energy of hydrolysis,
is moved from carbon 3
to carbon 2 to form 2phosphoglycerate.
C
H
O–
O
C
phosphoglycerate mutase
1
C
OH
2
H
C
CH2O P
2-phosphoglycerate
O–
O
The removal of
water from 2-phosphoglycerate
creates a high-energy enol
phosphate linkage.
C
C
enolase
O P
C
CH2OH
O–
O
C
C
C
pyruvate kinase
O P
H2O
phosphoenolpyruvate
O–
+
+
O P
CH2
2-phosphoglycerate
O
O–
O
C
H
O P
CH2OH
3
3-phosphoglycerate
Step 9
ATP
OH
1,3-bisphosphoglycerate
Step 8
Step 10
The transfer to
ADP of the high-energy
phosphate group that was
generated in step 9 forms
ATP, completing
glycolysis.
O–
O
phosphoglycerate kinase
C
H
NADH
OH
CH2O P
glyceraldehyde
3-phosphate
Step 7
+
C
ADP
+
+
H
C
O
CH2
CH3
phosphoenolpyruvate
pyruvate
+
ATP
O–
O
NET RESULT OF GLYCOLYSIS
C
CH2OH
O
HO
C
NADH
OH
ATP
CH3
ATP
OH
O–
O
OH
O
C
ATP
ATP
NADH
ATP
ATP
C
O
CH3
glucose
In addition to the pyruvate, the net products are
two molecules of ATP and two molecules of NADH.
two molecules
of pyruvate
+
H+