Cell Energy Releasing Reactions: Cellular Respiration

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Cell Energy Releasing ReactionsCellular
Respiration
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If this has left you confused and crazy in the
past..Lets make sense of it this time!!
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Energy Releasing Reactions

• Cellular Respiration involves
• Glycolysis
• Pyruvate Oxidation
• Krebs Cycle
• Oxidative Phosphorylation and Electron Transport

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Metabolism

• Sum of all chemical reactions in the cell
• Synthesis Reactions ANABOLISM
• Usually require energy Endergonic
• Example Photosynthesis
• Digestive Reactions CATABOLISM
• Usually release energy Exergonic
• Example Cell Respiration

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METABOLISM

• Involves linear pathways
• Involves cyclic pathways
• Involves a combination of linear and cyclic
  pathways
• Cell Respiration and Photosynthesis are combo
  pathways
• Pathways are enzyme catalyzed

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Biochemical Pathways

• Biochemical pathways are connected chemical
  reactions catalyzed by enzymes

A B
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Biochemical Pathways

• Biochemical pathways are connected chemical
  reactions

A B C
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Biochemical Pathways

• Biochemical pathways are connected chemical
  reactions

A B C D
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Biochemical Pathways

• Biochemical pathways are connected chemical
  reactions

A B C D E
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Catabolism

• Aerobic Respiration
• Uses oxygen as final electron acceptor
• Begins in cytoplasm completes in mitochondria
• Produces 36 ATP (38 in some cases)
  Fermentation (Anaerobic
  Respiration)
• Alternate pathway of catabolism
• Does not involve the use of oxygen
• Begins in cytoplasm completes in cytoplasm
• Produces 2 only ATP

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Catabolic PathwaysInvolved in Cell Respiration

• Glycolysis
• Pyruvate Oxidation
• Krebs Cycle
• Oxidative Phosphorylation
• Fermentation
• Others

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Catabolism

• Can be illustrated using a simple sugar molecule,
  glucose
• Glucose catabolism may utilize
• Glycolysis
• Prep Step (Pyruvate Oxidation) pre-Krebs
• Krebs Cycle
• Electron Transport System (also known as
  Oxidative Phosphorylation)

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Catabolism of Glucose via Aerobic Respiration
Glucose Oxygen 36 ADP 36 Phosphate
6 Carbon dioxide water 36 ATP heat

• Summary equation of reactions
• Glycolysis
• Prep Step
• Krebs Cycle
• ETS (Oxidative Phosphorylation)
• Breaks down glucose in stages

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Inter-relationship of respiratory pathways
Glucose
ATP
CO2
Pyruvate
Krebs Cycle
ATP
Reduced CoEnzymes
O2
CO2
H2O
Electron Transport Chain
ATP
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Glycolysis

• Conversion of 1 molecule glucose (6C)
• Into 2 molecules pyruvic acid (3C)
• Energy required 2 ATP
• Energy produced 4 ATP 2 NADH
• Net Energy for pathway 2 ATP 2 NADH
• Occurs in cytoplasm
• Oxygen not required for pathwayNEXT
• If no Oxygen, FERMENTATION occurs
• If Oxygen present, Pyruvic acid is oxidized,
  enters KREBS CYCLE

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GLYCOLYSIS
Glucose
Glucose-6-phosphate
Fructose-1,6-diphosphate
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PGAL
PGAL
GLYCOLYSIS
Diphosphoglyceric acid
3-Phosphoglyceric acid
Pyruvic acid
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Glycolysis Short Summary

• Occurs in cytoplasm
• Splits glucose (6 C sugar) into two pyruvic acid
  molecules (3 C each)
• Requires 2 ATPs to energize
• Produces 4 ATPs (2 ATPs net)
• Produces 2 NADH
• Important intermediate PGAL and end product
  Pyruvic acid

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Oxidation of Pyruvic Acid - preKrebs

• Pyruvic acid converted to acetyl-CoA
• 1 CO2 generated
• Energy produced 1 NADH
• Occurs in mitrochondria
• Usually not considered part of Krebs Cycle
• 2 pyruvic acids from glycolysis enter
• 2 acetyl Co-A molecules produced (to Krebs)
• 2 Carbon Dioxide molecules (to atmosphere)
• 2 NADH molecules produced (to ETS)

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Pyruvate Oxidation
Pyruvic Acid
Co-Enzyme A
NAD
Acetyl-CoEnzyme A
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Pyruvate Oxidation Summary

• Occurs in mitochondrial matrix
• Pyruvic acid converted to acetyl-CoA
• Acetyl- is a 2 carbon molecular group
• Attaches temporarily to CoEnzyme A
• CO2 is produced as waste
• NADH is produced in oxidation-reduction reaction
• Pyruvic acid from any source can be oxidized
  through this pathway

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Krebs Citric Acid Cycle

• Acetyl-CoA enters pathway, CoA released, acetyl
  joins oxaloacetic acid to form Citric Acid
• Series of oxidation/reduction reactions oxidizes
  acetyl to 2 CO2 molecules
• Oxaloacetic acid regenerated
• Energy Produced 1 ATP, 3 NADH, 1FADH2 for each
  acetyl that enters (x2)
• Occurs in mitochondrial matrix
• Glucose 2 pyruvic 2 acetyl gps 2
  turns of Krebs for each glucose

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acetyl-CoA
CoA
NAD
NADH
Citric acid
CO2
Oxaloacetic acid
NADH
a-ketoglutaric acid
KREBS CYCLE
NAD
NAD
ADP
NADH
Malic Acid
ATP
Succinic acid
CO2
Fumaric Acid
FAD
FADH2
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2
CoA
acetyl-CoA
Citric acid
Oxaloacetic acid
KREBS CYCLE
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3
acetyl-CoA
CoA
NAD
Citric acid
a-ketoglutaric acid
KREBS CYCLE
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4
acetyl-CoA
CoA
NAD
Citric acid
CO2
a-ketoglutaric acid
KREBS CYCLE
NAD
ADP
Succinic acid
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acetyl-CoA
CoA
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NAD
NADH
Citric acid
CO2
a-ketoglutaric acid
KREBS CYCLE
NAD
ADP
NADH
Malic Acid
ATP
Succinic acid
CO2
Fumaric Acid
FAD
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CoA
acetyl-CoA
NAD
NADH
Citric acid
CO2
Oxaloacetic acid
a-ketoglutaric acid
KREBS CYCLE
NAD
NAD
ADP
NADH
Malic Acid
ATP
Succinic acid
CO2
Fumaric Acid
FAD
FADH2
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Krebs Cycle Summary

• Occurs in mitochondrial matrix in eukaryotes
• Acetyl enters pathway via CoA- a shuttle link
  between Gly. and Krebs
• Each cycle oxidizes 2 Carbons as CO2 (to
  atmosphere) (x2)
• Each cycle produces 3 NADH, 1 FADH2, 1 ATP (NADH
  and FADH2 to ETS) (x2)
• Two cycles required per glucose
• Cycle regenerates itself (oxaloacetic acid)

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