The Citric Acid Cycle Follows Glycolysis

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The Citric Acid Cycle Follows Glycolysis
The citric acid cycle is more general than a
simple continuation of glycolysis. Fatty acids
enter the citric acid cycle. Amino acids enter
the citric acid cycle. Energy is liberated by
the catabolism of these molecules as well.
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The Citric Acid Cycle Also The Krebs Cycle Also
The Tri-carboxylic acid Cycle Concentrate
on The dehydrogenase reactions (Where CO2 is
blown off) The overall thermodynamics of the
cycle. (Why can it continue to go around and
around?)
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The Co-factor Acetyl-coenzyme A is a Major Input
to The Citric Acid Cycle (The Liberation of
Energy, Principally from Glucose Catabolism)
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The NAD / NADH The Principal Redox Pair in
Glycolysis and the Citric Acid Cycle
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Flavin Adenine Dinucleotide A Second Redox Active
Molecule in the Citric Acid Cycle
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Pyruvate is Decarboxylated and Enters the Citric
Acid Cycle as Acetyl-CoA
Focus!!!
Focus!!!
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Entry of Acetyl-CoA into the Citric Acid
Cycle Mechanism of Citrate Synthase
Citrate synthase converts oxaloacetate into
citrate Acetyl-CoA is a cofactor. DG -31.5
kJ/mol
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Second Reaction Isomerization of Citrate by
Aconitase
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The First Decarboxylation of the Citric Acid
Cycle Isocitrate Dehydrogenase and the Formation
of a-Ketoglutarate Generation of Reduced NADH
Precursor to glutamic acid
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a-Ketoglutarate Dehydrogenase The Production of
Succinyl-CoA Generation of the Second CO2.
1 equivalent of Acetyl-CoA has now been
completely oxidized to CO2.
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Succinyl-CoA Synthetase Production of
GTP Another Example of Substrate Level
Phosphorylation
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For the Citric Acid Cycle to be
Complete Succinate Must Be Converted to
Oxaloacetate Remaining Steps in the
Cycle Succinate Dehydrogenase
Production of reduced FADH2.
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Fumarase and the Conversion of Fumarate to Malate
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Malate Dehydrogenase and the Regeneration of
Oxaloacetate
DG 29.7 kJ/mol Production of reduced NADH
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Whats Driving the Citric Acid Cycle?
Citrate Synthase
Oxaloacetate Acetyl-CoA
Citrate DG 31.5 kJ/mol
Malate Dehydrogenase
Oxaloacetate DG 29.7 kJ/mol
Malate
Overall Reaction
The cycle
Acetyl-CoA Malate
Citrate DG 1.8 kJ/mol
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Production of Energy Storage Molecules in
Glycolysis and The Citric Acid Cycle
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The Electron Transport Chain and the Fate of
Reduced NADH and FADH2
The overall effect of the electron transport
chain is to pump protons into the intermembrane
space, generating an electrochemical gradient.
This gradient is the source of power for ATP
synthesis.
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The End
I would like sincerely to thank those of you who
have showed interest in the material demonstrate
d a serious concern for your own understanding of
the material stayed awake taken the time to
chat biochemistry with me. It has been a great
pleasure to work with you. I wish everyone good
luck on all your finals and I am at your disposal
during the finals period.
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Phosphate Transfer Reactions Play a Central Role
in Biochemistry Metabolism Energy
release Signaling Regulation
Enzymes which add phosphate to a substrate are
called kinases. Enzymes which remove
phosphate from a substrate are called phosphatases
.
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Oxidation / Reduction Reactions in
Biochemistry (esp. at C centers).
Carbon Compounds Exist in Many Different
Oxidation States Bound to a more
electronegative atom add 1. Bound to a less
electronegative atom subtract 1.