unit 2, lesson 4 part 2: oxidative phosphorylation

Summary of Glycolysis and Citric Acid Cycle

• Glycolysis converts glucose to 2 molecules of pyruvate and produces 2 ATP and 2 NADH.
• Pyruvate converts to acetyl coenzyme A, producing 2 NADH per glucose.
• The Citric acid cycle converts acetyl CoA to CO2 and produces 2 GTP, 6 NADH, and 2 FADH2.

Oxidative Phosphorylation Basics

• NADH and FADH2 react with oxygen in this process.
• The energy released during oxidative phosphorylation is then used to make ATP.
• Each molecule of NADH produces 3 ATP.
• Each molecule of FADH2 produces 2 ATP.
• When metabolized, each molecule of glucose gives rise to 36 molecules of ATP.
• Oxidative phosphorylation forms 32 molecules.

Location and Structure of Mitochondria

• Oxidative phosphorylation occurs inside the mitochondria.
• The mitochondria consists of the outer membrane, inner membrane, intermembrane space, cristae, and matrix.

Mitochondrial Structure

• The outer membrane binds the mitochondrion and is generally permeable to most small molecules.
• The highly folded inner membrane is virtually impermeable to all ions and polar molecules.
• The inner membrane contains specific transport proteins for some molecules, such as ADP, and is the site of oxidative phosphorylation .
• The matrix, bounded by the inner membrane, functions as the location of the citric acid cycle and fatty acid oxidation.

Electron Transport Chain

• Electrons transfer from NADH (or FADH2) to molecular oxygen via the electron transport chain.
• The electron transport chain has 4 protein complexes:
  • NADH-ubiquinone oxidoreductase (Complex I)
  • Succinate-ubiquinone oxidoreductase (Complex II)
  • Ubiquinol- cytochrome c oxidoreductase (complex III)
  • Cytochrome c oxidase (Complex IV)
• The 2 electron carriers are ubiquinone and cytochrome c.

Electron Transport from NADH

• Electrons are trasnferred to coenzyme Q, which carries electrons through the mebrane to complex III via NADH in complex I.
• Electrons are transferred to cytochrome c, the peripheral membrane protein carrying electrons to complex IV.
• The electron transfers reduce free energy in complexes I, III, and IV.
• Protons pump from the matrix to the intermembrane space in order to establish the proton gradient across the inner membrane.
• As protons flow back to the matrix through complex V, the energy stored is used to drive ATP synthesis.
• Complex IV transfers electrons to molecular oxygen.

Electron Transport from FADH2

• FADH₂ doesn't have as much reducing power as NADH.
• Each molecule of NADH produces 3 ATP.
• Each molecule of FADH2 produces 2 ATP.

Proton Motive Force

• NAD-Q reductase, cytochrome reductase, and cytochrome oxidase, pump protons out of the matrix of the mitochondrion.
• Pumping generates the proton motive force.

Oxidative Phosphorylation Summary

• Protons (H+) are pumped out of the mitochondrial matrix during oxidative phosphorylation .
• This pumping gives a proton gradient, which is an energy gradient
• The return of protons to the matrix is coupled to phosphorylation of ADP.

ATP Synthase (Complex V)

• The enzyme contains a transmembrane region and a large head group on the matrix side of the membrane.
• The head group contains the ATP synthesising domain.
• The transmembrane region makes the proton channel through which the protons flow.
• Two functional domains are F(1) and F(o).
  • F(1) is located in the mitochondrial matrix, and harvests free energy derived from proton movement.
  • F(o) is located in the inner mitochondrial membrane, which forms a channel helping protons cross the membrane.

Other Carbohydrates as Energy

• Sucrose converts into Glucose + Fructose.
• Maltose converts into Glucose.
• Starch converts into Glucose.

Lipids as energy sources

• Triglycerides convert into Glycerine + fatty acids.

Protein Energy Sources

• Alanine, Glycine, Cysteine, Serine, Threonine and Tryptophan convert into Pyruvate.
• Isoleucine, Leucine and Tryptophan convert into Acetyl CoA
• Leucine, Lysine, Phenylalanine, Tyrosine and Tryptophan convert into Acetoacetyl CoA.
• Aspartate and Asparagine convert into Oxaloacetate
• Tyrosine, Phenylalanine and Aspartate convert into Fumarate.
• Isoleucine, Methionine, Valine convert into Sucinyl CoA.
• Glutamate, Glutamine, Histidine, Proline, Arginine convert into alpha keto-glutarate

Metabolism of Glucose Summary

• ATP yield per glucose:
  • Glycolysis is 2
  • Citric acid cycle is 2
  • Oxidative phosphorylation is 32
  • Total is 36
• Efficiency:
  • Glucose + 6 02 converts into to 6 CO2 + 6 H2O
    • AG = -2881 KJ/mol
  • 36 ADP + 36 P converts into 36 ATP
    • AG = -1104 KJ/mol

Metabolic Activities

• Glycolysis is located in the Cytosol
• Citric acid cycle is located in the Mitochondria
• Oxidative phosphorylation is located in the Mitochondria