Chapter 14 H Ion Transport

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Chapter 14 H Ion Transport and ATP
Formation

• Introduction
• Evidence for chemiosmosis.
• The ATP synthase.
• How much ATP is actually made?

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• Introduction
• What is oxidative phosphorylation?
• Uses energy from the oxidation of
• NADH and FADH2 to make ATP.

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• Use the potential difference to
• provide energy for ATP formation
• Substrate level phosphorylation
• Oxidative phosphorylation

Peter Mitchell Chemiosmosis
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• Chemiosmosis
• El. Trans ? H ion gradient
• H ion gradient ? ATP

Intermemb. Space
NADH
Matrix
O2
e-
ET chain
H
H
H
High Conc.
Low Conc.
H
ADP ATP
H
H
ATP synthase
Inner mito. memb.
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Schematic of the inner mitochondrial membrane.
Complex ATP
I III IV synthase
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2. Evidence for chemiosmosis For chemiosmosis to
be correct, the following must be true. 1) The
membrane must be impermeable to H
ions. 2) Electron transport must produce
a hydrogen ion gradient. 3) The hydrogen ion
gradient must be able to produce ATP.
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1) A closed vesicle is required.
The inner mitochondrial membrane is a closed
system.
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What happens if you make the inner mitochondrial
membrane permeable to H ions?
Uncouplers compounds that inhibit ATP
formation by dissipating the H ion
gradient. Pores gramicidin H carriers
hydrophobic weak acids such as dinitrophenol

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O2
H
H
Intermemb. Space
NADH
Matrix
e-
ET chain
H
H
H
High Conc.
Low Conc.
H
ADP ATP
H
H
ATP synthase
Inner mito. memb.
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Control of the Rate of electron Transport.
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• Electron transport must be able
• to produce a H gradient. later.
• A H gradient alone must be able
• to produce ATP.

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3) A pH gradient can produce ATP without
electron transport.
Mito. ATP Synthase
Bqacterio- rhodopsin
Light
H
H
ATP is made.
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• How much energy can be stored in a H
• gradient?
• G 2.303 RT log Hto F DY
• Hfrom

F DY 2.303 RT D pH

Proton motive force
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Total PMF -19.4 kJ/mol ATP requires 32
kJ/mol Therefore, 2-3 H ions are required

• Mito Chloro
• pH 0.5 4.0
• Y 0.17V 0 V

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All membrane potential mito only H ions
move.
Build up large DY with few H
H
All proton gradient chloro Other ions move.
Potential drops Proton gradient is formed.
H
K
or
H
Cl-
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4. ATP synthase Coupling factor.
H ion channel
Synthesizes ATP
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H ions flow back through the ATP synthetase
Causing a change in shape or conformation
The conformational change provides the energy
for ATP formation
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How is ATP actually made? Binding change Paul
Boyer
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• How much ATP is actually made?
• Theoretical
• Transport of ATP, ADP and P
• NADH from the cytosol

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How many ATPs are actually made? Two
considerations.

• The maximum number of ATPs that can
• be formed are 3/NADH and 2/FADH2.

If we made the maximum, we would have Substrate
phos. 4ATP 10 NADH
30 ATP 2 FADH2 4 ATP Total
38 ATP
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In reality, there is an energy cost of 0.5 ATP.
ATP is produced on the inner surface of the
inner mitochondrial membrane.
Therefore, ADP must be brought in and ATP must
be exported costs energy 0.5 ATP.
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Transport of ATP, ADP and phosphate.
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Consideration 2.
Glycolysis occurs in the cytoplasm. NADH can not
cross the inner membrane.
Therefore, you need shuttles. 1. Glycerol/phosph
ate. 2. Malate/aspartate
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1. The glycerol phosphate shuttle
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Donates to Q.
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2. Malate-aspartate
Do not learn the details.
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If we made the maximum, we would have 2.5
ATP/NADH and 1.5 ATPFADH2 Substrate
phos. 4ATP 10 NADH
25 ATP 2 FADH2 3 ATP Total
32 ATP
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• Malate/aspartate
• No energy cost 2.5 ATP/ NADH
• kidney, liver and heart

2) Glycerol/phosphate Energy cost 1.5
ATP/glycolytic NADH brain skeletal muscle
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Malate/aspartate Glycerol-phosphate
Substrate phos. 4ATP
4 ATP 2 NADH from glycolysis 5 ATP
3 ATP 8 NADH from CA cycle 20 ATP
20 ATP
2 FADH2 3 ATP 3
ATP Total 32
ATP 30 ATP