Download Electron Transport Chain

Electron Transport Chain

Takes place in the cristae of mitochondrium


Electron acceptors are embedded in the cristae
Begins with electron from NADH


Reduces flavoprotein
Electron is passed to other molecules that have higher
electronegativity


Reduces new acceptor and donor is oxidated
Electron ultimately is accepted by O2 molecule


Very high electronegativity
For every 2 NADH molecules O2 is reduce to 2H2O
Electron Transport 2




Each new acceptor requires
that the electron be at a
slightly lower energy state
Energy is siphoned off of
the electrons in small
increments
The energy is used by the
acceptor molecules to
change conformation
All are proteins except Q
(ubiquinone) is lipid
Close-up of Cristae

Many electron acceptors used released energy to pump
an H+ proton into the intermembrane space

Gradient of H+ is formed outside of cristaes
Fig. 9-16
H+
H+
H+
H+
Protein complex
of electron
carriers
Cyt c
V
Q


ATP
synthase

FADH2
NADH
2 H+ + 1/2O2
H2O
FAD
NAD+
ADP + P i
(carrying electrons
from food)
ATP
H+
1 Electron transport chain
Oxidative phosphorylation
2 Chemiosmosis
Oxidative phosphorylation

ATP is actually synthesized
by enzyme ATP synthase


Hydrogen gradient needs to
reach equilibrium



Many copies embedded in
cristae
H+ can only pass through
ATP synthase molecule
Passage of H+ turns molecule
like a water wheel
ATP is generated by enzyme
action
Fig. 9-14
INTERMEMBRANE SPACE
H+
Stator
Rotor
Internal
rod
Catalytic
knob
ADP
+
P
i
ATP
MITOCHONDRIAL MATRIX
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Net ATP Production


Glycolysis 2 ATP, Krebs 2 ATP, Electron Transport &
oxidative phosphorylation 34 ATP
Total of 38 ATP/glucose
Fermentation


Used when oxygen is not available as electron
acceptor
Not as efficient as oxidative phosph.


In humans, only 2 ATP are produced by
fermentation
Accumulation of waste molecules

Sometimes can be used later as energy source

Type of fermentation is known by waste product
Types of Fermentation

Alcohol fermentation
Results in ethanol production
 Performed by bacteria and fungi


Lactic acid fermentation
Used by animals
 Results in lactate formation
 Causes muscles to ache after workout
 Anaerobic conditions

Fig. 9-18
2 ADP + 2 Pi
Glucose
2 ATP
Glycolysis
2 Pyruvate
2 NAD+
2 NADH
+ 2 H+
2 CO2
2 Acetaldehyde
2 Ethanol
(a) Alcohol fermentation
2 ADP + 2 Pi
Glucose
2 ATP
Glycolysis
2 NAD+
2 NADH
+ 2 H+
2 Pyruvate
2 Lactate
(b) Lactic acid fermentation
Why Fermentation



Pyruvate is dividing
point of two systems
If O2 is available
pyruvate enters
mitochondrium
If O2 level is low
Pyruvate stays in
cytosol and undergoes
fermentation
Macromolecules and Respiration

Many types of
macromolecules can be
used as a source for
respiration


Fats and proteins are
important
They enter pathway at
various point
Regulation of Respiration

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Very complex regulation
Feedback inhibition of
ATP or Citrate can stop
early stages of reactions
Allows cell to produce
ATP when needed