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GLUCOSE
2
Pentose phosphate
pathway
Starts the oxidation of glucose
Glycolysis
Oxidizes glucose to pyruvate
1
Yields
~
~
+
Reducing
power
ATP
by substrate-level
phosphorylation
Yields
Reducing
power
Biosynthesis
5
Acids, alcohols, and gases
Pyruvate
Pyruvate
3a
Fermentation
Reduces pyruvate
or a derivative
Transition step
CO2
CO2
Yields
Reducing
power
AcetylCoA
AcetylCoA
X2
CO2
CO2
3b
TCA cycle
Incorporates an acetyl
group and releases CO2
(TCA cycles twice)
Yields
~
ATP
by substrate-level
phosphorylation
~
+
Reducing
power
4
Respiration
Uses the electron transport
chain to convert reducing
power to proton motive force
Yields
~
ATP
by oxidative
phosphorylation
~
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Glycolysis
Pentose phosphate
pathway
Glucose 6-phosphate
Fructose 6-phosphate
Ribose 5-phosphate
Erythrose 5-phosphate
Nucleotides
amino acids
(histidine)
Amino acids
(phenylalanine,
tryptophan,
tyrosine)
Lipopolysaccharide
(polysaccharide)
Peptidoglycan
Dihydroxyacetone
phosphate
Lipids
(glycerol
component)
3-phosphoglycerate
Amino acids
(cysteine,
glycine, serine)
Phosphoenolpyruvate
Amino acids
(phenylalanine,
tryptophan, tyrosine)
Pyruvate
Pyruvate
Acetyl-CoA
Acetyl-CoA
Amino acids
(alanine,
leucine, valine)
Lipids
(fatty acids)
Oxaloacetate
Amino acids
(aspartate, asparagine,
isoleucine, lysine,
methionine, threonine)
X2
- ketoglutarate
Amino acids
(arginine, glutamate,
glutamine, proline)
TCA cycle
The Central Metabolic Pathways
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GLUCOSE
2
• Glycolysis
Pentose phosphate
pathway
Starts the oxidation of glucose
Yields
Glycolysis
Oxidizes glucose to pyruvate
1
P~ P~ P
+
Reducing
power
ATP
by substrate-level
phosphorylation
Yields
Reducing
power
Biosynthesis
5
Fermentation
Reduces pyruvate
or a derivative
Acids, alcohols, and gases
3a
Glucose
Transition step
– Converts 1 glucose
to 2 pyruvates; yields
net 2 ATP, 2 NADH
– Investment phase:
Yields
CO2
CO2
Reducing
power
• 2 phosphate groups
added
• Glucose split to two
3-carbon molecules
– Pay-off phase:
• 3-carbon molecules
converted to pyruvate
• Generates 4 ATP,
• 2 NADH total
Pyruvate
Pyruvate
x2
CO2
~ ~
ATP
CO2
3b
TCA cycle
Incorporates an acetyl
group and releases CO2
(TCA cycles twice)
~
ADP
Yields
P~ P ~ P +
ATP
by substrate-level
phosphorylation
1 ATP is expended to add a phosphate group.
Reducing
power
4
Respiration
Uses the electron transport
Chain to convert reducing
power to proton motive force
Yields
P~ P~ P
ATP
by oxidative
phosphorylation
Glucose
6-phosphate
2
A chemical rearrangement occurs.
Fructose
6-phosphate
~ ~
ATP
3
ATP is expended to add a phosphate group.
4
The 6-carbon molecule is split into two 3-carbon
molecules.
~
ADP
Fructose
1,6-bisphosphate
Dihydroxyacetone
phosphate
A chemical rearrangement of one of the
molecules occurs.
5
Glyceraldehyde
3-phosphate
NAD+
NADH + H+
1,3-bisphosphoglycerate
ADP
ATP
~
NAD+
6
NADH + H+
~
The addition of a phosphate
group is coupled to a redox
reaction, generating NADH and
a high-energy phosphate bond.
~
~
7
~ ~
~ ~
ATP is produced by
substrate-level
phosphorylation.
3-phosphoglycerate
8
2-phosphoglycerate
H2O
A chemical rearrangement occurs.
9
H2O
Phosphoenolpyruvate
ADP
ATP
Pyruvate
~
~ ~
~
~ ~
Water is removed, causing the
phosphate bond to become
high-energy.
10
ATP is produced by
substrate-level
phosphorylation.
The Central Metabolic Pathways
• Transition Step
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GLUCOSE
– CO2 is removed
from pyruvate
– Electrons reduce
NAD+ to
NADH + H+
– 2-carbon acetyl
group joined to
coenzyme A to form
acetyl-CoA
– Takes place in
mitochondria in
eukaryotes
2
Pentose phosphate
pathway
Starts the oxidation of glucose
Yields
Glycolysis
Oxidizes glucose to pyruvate
1
~
~
+
Reducing
power
ATP
by substrate-level
phosphorylation
Pyruvate
Yields
CO2
Reducing
power
Biosynthesis
Pyruvate
3a
Pyruvate
NAD+
Acids, alcohols, and gases
CoA
Transition step
CO2
Yields
Transition step:
CO2 is removed, a redox reaction generates
NADH, and coenzyme A is added.
Fermentation
Reduces pyruvate
or a derivative
5
CO2
Reducing
power
AcetylCoA
AcetylCoA
NADH + H+
x2
CO2
CoA
CO2
3b
TCA cycle
Incorporates an acetyl
group and releases CO2
(TCA cycles twice)
Acetyl-CoA
1 The acetyl group is transferred
to oxaloacetate to start a new
round of the cycle.
Yields
~
~
+
Reducing
power
ATP
by substrate-level
phosphorylation
CoA
Respiration
Uses the electron transport
chain to convert reducing
power to proton motive force
4
Yields
~
~
ATP
by oxidative
phosphorylation
NADH + H+
2 A chemical
rearrangement occurs.
Oxaloacetate
Citrate
A redox reaction
generates NADH.
8
NAD+
Isocitrate
NAD+
3
Malate
Water is added.
7
A redox reaction
generates NADH
and CO2 is
removed.
NADH + H+
H 2O
CO2
Fumarate
-ketoglutarate
NAD+
4
FADH2
6
CoA
A redox reaction
generates FADH2-
NADH + H+
FAD
5 The energy released
during CoA removal is
harvested to produce ATP.
CoA
Succinyl-CoA
Succinate
CoA
~ ~
ATP
~ + Pi
ADP
CO2
A redox reaction
generates NADH,
CO2 is removed,
and coenzyme A
is added.
The Electron Transport Chain of Mitochondria
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
GLUCOSE
2
Pentose phosphate
pathway
Starts the oxidation of glucose
Yields
1
Yields
Glycolysis
Oxidizes glucose to pyruvate
P ~ P ~P +
Reducing
power
ATP
by substrate-level
phosphorylation
Reducing
power
Biosynthesis
5
Pyruvate
Pyruvate
Eukaryotic cell
Fermentation
Reduces pyruvate
or a derivative
Acids, alcohols, and gases
3a Transition step
CO2
Yields
CO2
Reducing
power
AcetylCoA
AcetylCoA
x2
CO2
CO2
TCA cycle
3b
Incorporates an acetyl
group and releases CO2
(TCA cycles twice)
Yields
Inner
mitochondrial
membrane
Reducing
power
ATP
by substrate-level
phosphorylation
4
Respiration
Uses the electron transport
chain to convert reducing
power to proton motive force
Yields
P
P
ATP
by oxidative
phosphorylation
P
Complex III
Complex I
4
H+
4
Ubiquinone
+
Complex II
H+
NAD+
Complex IV
H+
2
Proton motive force
is used to drive:
H+
ATP synthase
(ATP synthesis)
10
H+
Cytochrome c
Intermembrane
space
2 e–
Path of
electrons
NADH
Use of Proton Motive Force
Electron Transport Chain
1/
2 H+
H2O
2
Mitochondrial
matrix
O2
Terminal
electron acceptor
3 ATP
+ 3 Pi
3 ADP
The Electron Transport Chain—Generating Proton
Motive Force
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Prokaryotic cell
Cytoplasmic
membrane
Electron Transport Chain
NADH dehydrogenase
Uses of Proton Motive Force
Ubiquinol
veoxidase
force
rive:
H+ (2 or 4)
H+ (0 or 4)
Ubiquinone
Path of
electrons
ATP synthase
(ATP synthesis)
Active transport
(one mechanism)
10 H+
Rotation of a flagella
H+
H+
Proton motive force
is used to drive:
Transported
molecule
Outside of
cytoplasmic
membrane
2 e– –
Cytoplasm
Succinate
dehydrogenase
NADH
+
NAD+
2 H+
1/
H2O
2
O2
Terminal
electron acceptor
H+
3 ATP
+ 3 Pi
3 ADP
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
GLUCOSE
2
Pentose phosphate
pathway
Starts the oxidation of glucose
1
Yields
Glycolysis
Oxidizes glucose to pyruvate
P ~ P~ P
+
Reducing
power
ATP
by substrate-level
phosphorylation
Yields
Fig. 6.22
Reducing
power
Biosynthesis
Fermentation
Reduces pyruvate
or a derivative
5
Pyruvate
Pyruvate
Acids, alcohols, and gases
Transition step
3a
Yields
CO2
CO2
Reducing
power
AcetylCoA
AcetylCoA
x2
CO2
CO2
3b
TCA cycle
Incorporates an acetyl
group and releases CO2
(TCA cycles twice)
Yields
P ~ P ~ P
Reducing
power
+
ATP
by substrate-level
phosphorylation
4
Respiration
Uses the electron transport
chain to convert reducing
power to proton motive force
Yields
P ~ P ~ P
ATP
by oxidative
phosphorylation
NAD+
NADH + H+
H3C
O
O
C
C
O–
H3C
OH
O
C
C
O–
H
Lactate
Pyruvate
(a) Lactic acid fermentation
CO2
H3C
O
O
C
C
NADH + H+
NAD+
O
O–
Pyruvate
(b) Ethanol fermentation
H3C
C
OH
H
Acetaldehyde
H3C
C
H
Ethanol
H