Glucose Metabolism Glycolysis Chapter 14

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Glucose MetabolismGlycolysisChapter 14
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Glucose (6C)
Glycolysis
2 pyruvate (3C)
Ethanol fermentation
Lactic acid fermentation
Respiration
Anaerobic
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Keep track of CO2 released ATP formed High energy
electrons stored
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Glucose Metabolism
Glucose (6C) 2 Pyruvate (3C)
2ATP
2NADH
Glycolysis
4ATP
2ATP
2 ATP
6CO2
8NADH 2FADH2
Ethanol CO2
Lactate (3C)
Anaerobic glycolysis
2ATP
Anaerobic alcohol Fermentation
Aerobic Respiration
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Glycolysis
Energy yield 2 ATP 2 NADH
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Glucose
Phase 1 Energy Requiring

Uses 2 ATP
Phase 2 Energy yielding
Yields 4 ATP
Pyruvate
Net 2 ATP
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Glucose
Glycolysis
Activating energy- requiring
2ADP 2P
2ATP
Fructose-1,6-bisphosphate
4ATP
4ADP 4P
2NADH
2 pyruvate
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1
Hexokinase
H
HO
Glucose-6-P
Glucose
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Types of Enzymatic Reactions

• Kinase Transfers a phosphate from
• ATP to a substrate.

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Reaction 1
Conversion of glucose to glucose-6-P
Glucose Pi ? Glucose-6-phosphate H2O
DGo 3.3 kcal/mole
ATP H2O ? ADP Pi
DGo -7.3 kcal/mole
Glucose ATP ? glucose-6-P ADP
DGo -4.0 kcal/mole
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Glucosephosphate isomerase
2
Glucose 6-P
Fructose 6-P
Aldose
Ketose
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Types of Enzymatic Reactions

• Kinase Transfers a phosphate from
• ATP to a substrate.
• Isomerase Transforms an aldehyde to
• a ketone vice-versa.

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Phosphofructokinase
ADP
Fructose 6-P
Fructose-1,6-bis-P
2 molecules of ATP used thus far.
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Glucose
Glycolysis
Activating energy- requiring
2ADP 2P
2ATP
Fructose-1,6-bisphosphate
4ATP
4ADP 4P
2NADH
2 pyruvate
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Energy-yielding
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Aldolase
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Types of Enzymatic Reactions

• Kinase Transfers a phosphate from
• ATP to a substrate.
• Isomerase Transforms an aldehyde to
• a ketone vice-versa.
• 3. Aldol condensation Condensation of an
• aldehyde and a ketone.

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Triosephosphate isomerase
Dihydroxyacetone phosphate
D-glyceraldehyde 3-phosphate
Net 2 molecules of D-glycerladehy-3P for each
glucose you start with.
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Types of Enzymatic Reactions contd.

• Dehydrogenase Removes two elections
• and 2 H ions from a substrate and transfers
• them to NAD or FAD.

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Dehydrogenases

• the -CHO group is oxidized to a carboxyl group
• the oxidizing agent, NAD, is reduced to NADH

NADH
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Glyceraldehyde 3-phosphate dehydrogenase
H
High energy bond
Glyceradehyde 3-P
Aldehyde
Reduction
1,3-bisphosphoglycerate
Oxidation
Acid
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Energetics
DG ooverall DG ooxidation DG
ophosphorylation
-43.1 kJ/mol
49.3 kJ/mole
Net 6kJ/mole 1.5 kcal/mole
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Phosphoglycerate kinase
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ATP is formed by substrate phosphorylation
Directly by an enzymatic reaction
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What is the DGo ?
1,3-bisphosphoglycerate?3-phosphoglycerate Pi
DGo -11.8 kcal/mol
ADP Pi ? ATP
DGo 7.3 kcal/mole
1,3-bisphosphoglycerate ADP ?
3-phosphoglycerate ATP
DGo -4.5 kcal/mol
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• Important points
• Glycolysis is a very important
• pathway in the metabolism of glucose.
• In glycolysis, 1 molecule of glucose is
• converted into 2 molecules of pyruvate
• with the net formation of 2 molecules
• of NADH and 2 molecules of ATP

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3. Glycolysis can be divided into two phases
(1) energy-requiring and (2) energy-releasing.
4. In the energy-requiring steps, 2 ATP
are used and 1 fructose-1,6-bisphosphate is
formed.
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• In the energy-yielding steps,
• 2 molecules of pyruvate,
• 4 molecules of ATP
• and 2 NADH molecules are produced.

6. Glycolysis yields only 2 ATP Net because 2
ATPs are utilized in the energy requiring
steps.