Theme E: oxidative phosphorylation Steps of aerobic respiration
A study of the electron transport chain and oxidative • Glycolysis
phosphorylation as coupled processes by means of which - breakdown of glucose to pyruvate (with production of
cellular reducing equivalents use a series of redox reactions to ATP and NADH)
supply energy for the formation of ATP from ADP and Pi • Pyruvate oxidation
- conversion of pyruvate to an activated 2C-fragment
Lecture E1 – reduction potentials, mitochondrial structure,
(acetyl-CoA) (with production of NADH and CO2)
metabolite shuttles (pg. 96-98, 484-488, 508-509)
• Citric acid cycle
Overview of aerobic respiration - oxidation of acetyl-CoA → 2CO2 (with production of
GTP/ATP, NADH and FADH2)
• Oxidative phosphorylation
- oxidation of reduced electron carriers (NADH/FADH2) to
produce more energy (ATP)
What is oxidative phosphorylation
• Exergonic oxidation of electron carriers by electron
transport system linked to endergonic synthesis of ATP by
ATP-synthase complex
- oxidation: release of e- & H+
- electron carriers: NADH & FADH2
- electron transport system = electron transport chain
(ETC)
- ATP synthesis: ADP + Pi → ATP
• O2 final electron acceptor
Electron carriers (reducing equivalents)
• Substrates for oxidative phosphorylation:
- glycolysis (NADH)
- pyruvate oxidation (NADH)
- citric acid cycle (NADH and FADH2)
, - Matrix
- but ATP-synthase complex (V) in inner membrane
- linked to oxidation of electron carriers
Site of oxidative phosphorylation (structure of mitochondria)
• ETC components (Lecture E2)
- Complex I, II, III, IV; CoQ; Cyt c
- inner membrane
- accepts e- from electron carriers
• ATP synthesis
, Oxidation of electron carriers Reduction potential (E)
• Oxidation through the process of redox reactions • Measure of the tendency of the oxidizing agent to gain
• Basic principles of redox reactions: electrons / the reducing agent to lose electrons (i.e. the
tendency of electrons to be transferred)
• Such a measure/index is provided by the:
- Standard reduction potential = Eº
- Standard reduction potential at pH 7.0 = Eº’
- Standard SI-unit: Volt (V)
An oxidising and reducing agent which appear on opposite sides of
a half reaction (equation) constitute a redox couple. A redox
couple is a reducing species and its corresponding oxidizing form,
e.g., Fe2+/Fe3+
Redox reactions in ETC (example)
Measuring reduction potential (E)
• Eº/Eº’ measured relative to a reference standard
• Reference standard:
- reduction of H+ to H2 (hydrogen gas)
• Conditions to measure Eº/ Eº’:
- reference half-cell contains [H+] = 1 M, H2 = 1 bar
- test half-cell contains e--donor and conjugate acceptor
at 1 M each
- T = 25°C
- pH = 0 ([H+] = 1M) for Eº or pH = 7 ([H+] = 10-7M) for Eº’
- reference electrode set to 0.00 V
(1 bar = the standard unit of pressure = 100 kPa)
A study of the electron transport chain and oxidative • Glycolysis
phosphorylation as coupled processes by means of which - breakdown of glucose to pyruvate (with production of
cellular reducing equivalents use a series of redox reactions to ATP and NADH)
supply energy for the formation of ATP from ADP and Pi • Pyruvate oxidation
- conversion of pyruvate to an activated 2C-fragment
Lecture E1 – reduction potentials, mitochondrial structure,
(acetyl-CoA) (with production of NADH and CO2)
metabolite shuttles (pg. 96-98, 484-488, 508-509)
• Citric acid cycle
Overview of aerobic respiration - oxidation of acetyl-CoA → 2CO2 (with production of
GTP/ATP, NADH and FADH2)
• Oxidative phosphorylation
- oxidation of reduced electron carriers (NADH/FADH2) to
produce more energy (ATP)
What is oxidative phosphorylation
• Exergonic oxidation of electron carriers by electron
transport system linked to endergonic synthesis of ATP by
ATP-synthase complex
- oxidation: release of e- & H+
- electron carriers: NADH & FADH2
- electron transport system = electron transport chain
(ETC)
- ATP synthesis: ADP + Pi → ATP
• O2 final electron acceptor
Electron carriers (reducing equivalents)
• Substrates for oxidative phosphorylation:
- glycolysis (NADH)
- pyruvate oxidation (NADH)
- citric acid cycle (NADH and FADH2)
, - Matrix
- but ATP-synthase complex (V) in inner membrane
- linked to oxidation of electron carriers
Site of oxidative phosphorylation (structure of mitochondria)
• ETC components (Lecture E2)
- Complex I, II, III, IV; CoQ; Cyt c
- inner membrane
- accepts e- from electron carriers
• ATP synthesis
, Oxidation of electron carriers Reduction potential (E)
• Oxidation through the process of redox reactions • Measure of the tendency of the oxidizing agent to gain
• Basic principles of redox reactions: electrons / the reducing agent to lose electrons (i.e. the
tendency of electrons to be transferred)
• Such a measure/index is provided by the:
- Standard reduction potential = Eº
- Standard reduction potential at pH 7.0 = Eº’
- Standard SI-unit: Volt (V)
An oxidising and reducing agent which appear on opposite sides of
a half reaction (equation) constitute a redox couple. A redox
couple is a reducing species and its corresponding oxidizing form,
e.g., Fe2+/Fe3+
Redox reactions in ETC (example)
Measuring reduction potential (E)
• Eº/Eº’ measured relative to a reference standard
• Reference standard:
- reduction of H+ to H2 (hydrogen gas)
• Conditions to measure Eº/ Eº’:
- reference half-cell contains [H+] = 1 M, H2 = 1 bar
- test half-cell contains e--donor and conjugate acceptor
at 1 M each
- T = 25°C
- pH = 0 ([H+] = 1M) for Eº or pH = 7 ([H+] = 10-7M) for Eº’
- reference electrode set to 0.00 V
(1 bar = the standard unit of pressure = 100 kPa)
