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Glucose metabolism

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Not very user-friendly. How to harvest the energy? Electron transport chain ... not yet useable. DE' 0 ~ DG' 0. Electrons are passed among. redox carriers ... – PowerPoint PPT presentation

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Title: Glucose metabolism


1
Glucose metabolism
  • Glycolysis 2 NADH, 2 ATP (net)
  • Pre-TCA cycle 2 NADH
  • TCA cycle 6 NADH, 2 FADH2, 2 A/GTP

Some ATP Big bonus NADH, FADH2 ? REDUCING POWER
2
Energy harvest by respiration
  • Carbon-carbon bonds chemical energy
  • NADH, FADH2 energy of oxidation
  • Proton gradient potential energy
  • ATP synthesis useable chemical energy

3
Reducing power/Energy of oxidation
  • Not very user-friendly
  • How to harvest the energy?
  • Electron transport chain
  • Change energy of oxidation into potential energy
    (H gradient)
  • Change potential energy into chemical energy
  • (F1Fo ATP synthase)

4
What is energy of oxidation?
  • Reducing potentials
  • NAD H 2e- ? NADH E' -0.414V
  • ubiquinone 2H 2e- ? ubiquinol E' 0.045
  • Electrons (e-) flow spontaneously from NADH to
    ubiquinone

NADH IS A STRONGER REDUCING AGENT THAN UBIQUINOL
ubiquinone
NADH
(oxidized form)
(reduced form)
5
Cataloging the red/ox reactionTransfer of e-
from NADH to ubiquinone
E' (V)
NADH ? NAD H 2e-
0.414
ubiquinone 2H 2e- ? ubiquinol
0.045
NADH ubiquinone H ? ubiquinol NAD
0.459
extra energy not yet useable
DE' gt 0 DG' lt 0
6
Electrons are passed among redox carriers
REDUCINGSTRENGTH
NADH?NAD
FMN (?FMNH2)
Fe-S Cluster
Ubiquinone (coenzyme Q)
Cytochrome C
Couple energetically favorable reactions to
energetically unfavorable reactions Overall -DG
O2?H2O
7
Redox energy is transformed into potential energy
MATRIX
Generation of NADH
INTERMEMBRANESPACE
8
Flow of H into the matrix Is energetically
favorable 1. Input energy to move H
out 2. Harvest energy
INTERMEMBRANESPACE
Low pH (higher H) Electrically positive
MATRIX
High pH (lower H) Electrically negative
9
Mitochondria actually look like the cartoons
http//www.tmd.ac.jp/
http//faculty.ircc.edu
10
Redox energy is transformed into potential energy
Establishment of a chemical and electric gradient
across the inner membrane
F1Fo ATP synthase Transforms potential Energy
into useable Chemical energy
11
Electron transport between electron carriers
occurs in protein complexes within the inner
membrane
12
Complex I
  • NADH Ubiquinone oxidoreductase
  • 850kDa, 43 subunits
  • Converts NADH to NAD
  • e- transferred through complex
  • FMN, Fe-S clusters
  • 4 protons are pumped from the matrix into the
    intermembrane space
  • Reduces ubiquinone (Q) to ubiquinol (QH2)

13
Ubiquinol (reduced coenzyme Q)
14
Complex III
  • Coenzyme Qcytochrome c oxidoreductase
  • 250 kDa
  • 11 subunits
  • 2 coQ oxidized, one CytC reduced
  • e- carriers
  • Hemes, Fe-S clusters
  • Net 4 H pumped to intermembrane space

15
Complex III, cont.
16
Cytochrome C
  • Heme group carries electrons
  • Loosely associated with membrane
  • Shuttles e- from complex III to IV

17
Complex IV
  • Cytochrome C oxidase
  • 160 kDa
  • 13 subunits
  • Reduces oxygen
  • ½ O2 2H 2e- ? H2O

18
Complex II (Use of FADH2)
  • Succinate dehydrogenase
  • Membrane-bound enzyme in the TCA cycle
  • 140 kDa
  • 4 subunits
  • FAD, Fe-S clusters carry electrons
  • e- transferred ubiquinone(Q)
  • QH2 carries e- to complex 3

19
Electron transport
20
Overall reaction starting with 2 e- from one NADH
NADH H ½ O2 ? NAD H2O
DG' -220 kJ/mol (of NADH) -highly
favorable -coupled to transport of 10 H
against a chemical/electrical gradient
21
(No Transcript)
22
Oxidative phosphorylation
  • Involves reduction of O2 to H2O by NADH and FADH2
  • ATP synthesized through e- transfers
  • Inner mitochondrial membrane
  • Embedded protein complexes
  • Succinate dehydrogenase
  • Impermeable to most small molecules (and H)
  • Creation of electrochemical gradients

23
ATP generation
  • 2 NADH, 2 ATP from glycolysis (glucose)
  • 1 NADH from pre-TCA (each pyruvate)
  • 3 NADH, FADH2 from TCA (each acetyl CoA)
  • 2 e- from NADH? yields 2.5 ATP
  • 2 e- from FADH2 ? yields 1.5 ATP
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