Mic201 Lecture

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Mic201 - Lecture 10 Outline Catabolism- Major
Catabolic Pathways (2nd. Part)

• Aerobic respiration carbon and electron
  transformations.
• Membrane-associated electron carriers 2
  functions.
• Different membrane-associated electron carriers.
• Energy conservation from the Proton Motive Force
  (PMF).
• Oxidative phosphorylation.
• Major components of electron transport chains.
• How is electron transport linked to ATP
  synthesis?
• How is the electron transport system oriented in
  the membrane?

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• Aerobic respiration deals both with carbon and
  electron transformations.
• How does the PMF drive ATP synthesis?
• Carbon flow in respiration the Krebs (or TCA)
  cycle.
• Overall reactions and energy yield.
• Catabolic diversity.
• Biosynthesis and the CA cycle.
• Summary

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Aerobic respiration
The process by which a compound is oxidized using
O2 as the terminal electron acceptor.
Aerobic respiration deals both with carbon and
electron transformations. 1. Biochemical pathway
involved in the transformation of organic carbon
to CO2 2. Electrons are transferred from the
organic compound to the terminal electron
acceptor, driving ATP synthesis.
(We will start discussing this last aspect)
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Membrane-associated electron carriers 2
functions.
To accept electrons from an electron donor and
transfer them to an electron acceptor.
To conserve some of the energy released during
electron transfer for synthesis of ATP.
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Different membrane-associated electron carriers

• NADH dehydrogenases
• Flavoproteins (riboflavin-containing electron
  carriers)
• Iron-sulfur proteins
• cytochromes

Non-protein electron carriers lipid soluble
quinones
Look at the structures in your textbook
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Different membrane-associated electron carriers
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• NADH dehydrogenases
• Flavoproteins (riboflavin-containing electron
  carriers)
• Iron-sulfur proteins
• cytochromes

Non-protein electron carriers lipid soluble
quinones
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Do you remember the electron tower?
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Major components of electron transport chains
Figure 5.19
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Energy conservation from the Proton Motive Force
(PMF).
Separation of H from e- occurs across the
membrane during the transport process. ?
Slight acidification of the external surface of
the membrane.
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The energized membrane
Slightly positive
Slightly negative
Slightly positive
Slightly positive
Slightly negative
Slightly negative
Slightly negative
Slightly positive
H
Pumped outside the cell
H atoms
e-
transported
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Generation of the proton motive force during
aerobic respiration
pH gradient and electrochemical potential.
Figure 5.20
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Generation of PMF
Electron transport scheme common features

• Presence of a series of membrane-associated
  electron carriers arranged in order of
  increasingly more positive Eo.
• An alternation in the chain on electron-only and
  hydrogen-atom only carriers.
• The presence of a PMF as a result of charge
  separation across the membrane.

How does the PMF drive ATP synthesis?
ATPase Fo and F1
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Structure and function of ATP synthase (ATPase).
headpiece
Proton-conducting channel
Figure 5.21
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Aerobic respiration deals both with carbon and
electron transformations.
1. Biochemical pathway involved in the
transformation of organic carbon to CO2 2.
Electrons are transferred from the organic
compound to the terminal electron acceptor,
driving ATP synthesis.
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Carbon flow in respiration the Krebs (or TCA)
cycle.
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CAC cycle TCA cycle Krebs cycle
Figure 5.22
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Figure 5.22b
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Catabolic diversity
Anaerobic respiration Chemolithotrophy Phototrophy
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