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Electron Transport and Oxidative Phosphorylation. It all reduces down to water. Mitochondria. outer membrane relatively permeable inner membrane permeable only to those things with specific transporters Impermeable to NADH and FADH 2 Permeable to pyruvate Compartmentalization

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mitochondria
Mitochondria
  • outer membrane relatively permeable
  • inner membrane permeable only to those things with specific transporters
    • Impermeable to NADH and FADH2
    • Permeable to pyruvate
  • Compartmentalization
    • Kreb's and β-oxidation in matrix
    • Glycolysis in cytosol
most energy from redox
Most energy from Redox
  • electrons during metabolic reactions sent to NAD and FAD
    • Glycolysis
      • In cytosol
      • produces 2 NADH
    • Pyruvate dehydrogenase reaction
      • In mitochondrial matrix
      • 2 NADH / glucose
    • Krebs
      • In mitochondrial matrix
      • 6 NADH and 2 FADH2 / glucose
electron transport chain
Electron Transport Chain
  • Groups of redox proteins
    • On inner mitochondrial membrane
    • Binding sites for NADH and FADH2
      • On matrix side of membrane
      • Electrons transferred to redox proteins
      • NADH reoxidized to NAD+
      • FADH2 reoxidized to FAD
4 complexes
4 Complexes
  • proteins in specific order
  • Transfers 2 electrons in specific order
    • Proteins localized in complexes
      • Embedded in membrane
      • Ease of electron transfer
    • Electrons ultimately reduce oxygen to water
      • 2 H+ + 2 e- + ½ O2 -- H2O
complex 1
Complex 1
  • Has NADH binding site
    • NADH reductase activity
      • NADH - NAD+
    • NADH ---> FMN--->FeS---> ubiquinone
    • ubiquinone ---> ubiquinone H2
    • 4 H+ pumped/NADH
complex ii
Complex II
  • succinate ---FAD—ubiquinone
    • Contains coenzyme Q
    • FADH2 binding site
      • FAD reductase activity
      • FADH2 -- FAD
complex iii
Complex III
  • ubiquinone - ubiquinone ox
  • while cyt C gets reduced
  • Also contains cytochromes b
    • proton pump 4H+
      • Adds to gradient

8 H+ / NADH

4 H+ / FADH2

complex iv
Complex IV
  • reduction of oxygen
  • cytochrome oxidase
  • cyt a+a3 red ---> oxidized state
  • oxygen ---> water
    • 2 H+ + 2 e- + ½ O2 -- 2 H2O
    • transfers e- one at a time to oxygen
  • Pumps 2H+ out
    • Total of 10 H+ / NADH
    • Total of 6 H+ / FADH2
totals
Totals
  • Proton gradient created as electrons transferred to oxygen forming water

10 H+ / NADH

6 H+ / FADH2

generation of atp
Generation of ATP
  • Proton dependant ATP synthetase
    • Uses proton gradient to make ATP
    • Protons pumped through channel on enzyme
      • From intermembrane space into matrix
      • ~4 H+ / ATP
    • Called chemiosmotic theory
totals17
Totals

NADH

10 H+ X 1 ATP = 2.5 ATP

4 H+

FADH2

6 H+ X 1 ATP = 1.5 ATP

4 H+

total atp from mitochondrial matrix
Total ATP from mitochondrial matrix
  • Pyruvate dehydrogenase
    • NADH ……………………………….2.5 ATP
  • Krebs

3 NADH X 2.5 ATP/NADH ……….7.5 ATP

FADH2 X 1.5 ATP / FADH2……….1.5 ATP

GTP X 1 ATP / GTP ……………..1.0 ATP

(from a separate reaction)

Total …………….12.5 ATP

(Per glucose = X 2 = 25 ATP)

what about nadh from glycolysis
What about NADH from glycolysis?
  • NADH made in cytosol
  • Can’t get into matrix of mitochondrion
  • 2 mechanisms
    • In muscle and brain
      • Glycerol phosphate shuttle
    • In liver and heart
      • Malate / aspartate shuttle
glycerol phosphate shuttle
Glycerol Phosphate shuttle
  • http://courses.cm.utexas.edu/jrobertus/ch339k/overheads-3/ch19_glycerol-shuttle.jpg
glycerol phosphate shuttle21
Glycerol phosphate shuttle
  • In muscle and brain
  • Each NADH converted to FADH2 inside mitochondrion
    • FADH2 enters later in the electron transport chain
    • Produces 1.5 ATP
total atp per glucose in muscle and brain
Total ATP per glucose in muscle and brain
  • Gycerol phosphate shuttle
    • 2 NADH per glucose - 2 FADH2
    • 2 FADH2 X 1.5 ATP / FADH2……….3.0 ATP
    • 2 ATP in glycoysis ……………………2.0 ATP
    • From pyruvate and Krebs
      • 12.5 ATP X 2 per glucose ……………..25.0 ATP

Total = 30.0 ATP/ glucose

malate aspartate shuttle
Malate – Aspartate Shuttle
  • http://courses.cm.utexas.edu/emarcotte/ch339k/fall2005/Lecture-Ch19-2/Slide14.JPG
malate aspartate shuttle in cytosol
Malate – Aspartate Shuttlein cytosol
  • In liver and heart
  • NADH oxidized while reducing oxaloacetate to malate
    • Malate dehydrogenase
  • Malate crosses membrane
malate aspartate shuttle in matrix
Malate – Aspartate Shuttlein matrix
  • Malate reoxidized to oxaloacetate
    • Malate dehydrogenase
    • NAD+ reduced to NADH
  • NADH via electron transport yields 2.5 ATP

Mlate – Aspartate Shuttlein cytosol

total atp per glucose in liver and heart
Total ATP per glucose in liver and heart
  • Malate – Aspartate Shuttle
    • 2 NADH per glucose - 2 NADH
    • 2 NADH X 2.5 ATP / NADH…………5.0 ATP
    • 2 ATP from glycolysis………………..2.0 ATP
    • From pyruvate and Krebs
      • 12.5 ATP X 2 per glucose ……………..25.0 ATP

Total = 32.0 ATP/ glucose

summary
Summary
  • Total ATP / glucose
    • Muscle and brain 30.0 ATP
      • Uses glycerol phosphate shuttle
    • Heart and liver 32.0 ATP
      • Uses malate aspartate shuttle