Biology 100
CHEMIOSMOTIC SYNTHESIS OF ATP
2/16/16
4th ed.
11.3.8 F-Type ATPases are reversible, ATP-driven Proton Pumps
p. 401
19.1 Electron Transfer Reactions in Mitochondria (listed subsections only)
Electrons are Funneled to Universal Electron Acceptors
Electrons Pass Through a Series of Membrane-Bound Carriers
Electron Carriers Function in Multienzyme Complexes
The Energy of Electron Transfer is Efficiently Conserved in a Proton Gradient
19.2 ATP SYNTHESIS (listed subsections only)
The Energy of Electron Transfer is Efficiently Conserved in a Proton Gradient
ATP Synthase Has Two Functional Domains, Fo And F1
ATP Is Stabilized Relative To ADP On The Surface Of F1
The Proton Gradient Drives The Release Of ATP From The Enzyme Surface
Each B Subunit Of ATP Synthase Can Assume Three Different Conformations
Rotational Catalysis Is Key To Binding-Change Mechanism For ATP Synthesis
Chemiosmotic Coupling Allows Non-Integral Stoichiometries Of O2 Consumption And
ATP Synthesis
SUGGESTED PROBLEMS:
Chap. 19: #1, 2, 3, 4, 5, 6, 7, 8, 14
5th ed.
11.3.7 F-Type ATPases are reversible, ATP-driven Proton Pumps
p. 399
19.1 Electron Transfer Reactions in Mitochondria (listed subsections only)
Electrons are Funneled to Universal Electron Acceptors
Electrons Pass Through a Series of Membrane-Bound Carriers
Electron Carriers Function in Multienzyme Complexes
The Energy of Electron Transfer is Efficiently Conserved in a Proton Gradient
19.2 ATP SYNTHESIS (listed subsections only)
ATP Synthase Has Two Functional Domains, Fo And F1
ATP Is Stabilized Relative To ADP On The Surface Of F1
The Proton Gradient Drives The Release Of ATP From The Enzyme Surface
Each B Subunit Of ATP Synthase Can Assume Three Different Conformations
Rotational Catalysis Is Key To Binding-Change Mechanism For ATP Synthesis
Chemiosmotic Coupling Allows Non-Integral Stoichiometries Of O2 Consumption And
ATP Synthesis
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Biology 100
CHEMIOSMOTIC SYNTHESIS OF ATP
2/16/16
SUGGESTED PROBLEMS:
Chap. 19: #1, 2, 3, 4, 5, 6, 7, 8, 16
19.1 Electron Transfer Reactions in Mitochondria (listed subsections only)
Chemiosmosis is the synthesis of ATP (by phosphorylation of ADP) using energy
derived from an elctro-chemical gradient of H+ across a membrane.
Chemiosmosis should be contrasted to ATP synthesis by “Substrate–Level
Phosphorylation” where ADP phosphorylation is driven by coupling to an exergonic
chemical reaction.
Chemiosmosis occurs in:
Bacterial Plasma Membranes
Bacterial Thylakoid (Photosynthetic) Membranes
Inner Mitochondrial Membrane
Chloroplast Thylakoid Membrane
Electrons are Funneled to Universal Electron Acceptors
You don't need to memorize all the examples in Table 19-1
Electrons Pass Through a Series of Membrane-Bound Carriers
You don't need to know the structural differences among the heme groups in Fig. 19-3.
You should recognize the 3 types of Fe-S centers (Fig. 19-5).
Electron Carriers Function in Multienzyme Complexes
You are responsible for the details of Complex IV only. You are responsible for general
information about the other complexes. You are not responsible for the "Q Cycle"
(Fig. 19-12).
The Energy of Electron Transfer is Efficiently Conserved in a Proton Gradient
11.3.7 F-Type ATPases are reversible, ATP-driven Proton Pumps
p. 399
19.2 ATP SYNTHESIS (listed subsections only)
"Uncouplers"
"ATP Synthase" pseudo-synonyms:
F-type ATPase
Proton-Translocating ATPase
Complex V
ATP Synthase Has Two Functional Domains, F o And F1
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Biology 100
CHEMIOSMOTIC SYNTHESIS OF ATP
FO Domain
2/16/16
Integral membrane component
H+ channel operates in absence of F1
a1 b2 c9-14 subunit structure
H+ blocked by reaction with DCCD or Oligomycin B
Each c subunit is composed of 2 hydrophobic helices perpendicular
to membrane. #c subunits variable with species
F1 Domain
Cytosolic Component
  
3 concentric  dimers


site
ATP Is Stabilized Relative To ADP On The Surface Of F 1
The Proton Gradient Drives The Release Of ATP From The Enzyme Surface
Hydrolysis of F1-bound ATP is freely reversible (Go’ = ~ 0 kJ/mol; Keq = near 1 vs 105
for free solution). Stabilization of ATP relative to ADP (40 kJ/mol ) accomplished by
strong ATP binding.
KdATP = 10-12 in high affinity (tight) conformation; KdATP = 10-5 in low affinity (loose)
conformation (KdADP = 10-5).
Each B Subunit Of ATP Synthase Can Assume Three Different Conformations
Rotational Catalysis Is Key To Binding-Change Mechanism For ATP Synthesis
“ROTOR” rotates with respect to
F1
Fo
STATOR


a
b
ROTOR


c
Boyer Model – eccentric cam analogy/rotational catalysis. Another example of
dynamic quaternary protein structure and an inspirational model for nanomachine
engineering.
One rotation:


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Biology 100
CHEMIOSMOTIC SYNTHESIS OF ATP
2/16/16
9 H+ are translocated (approximate 3 H+ per ATP)
Chemiosmotic Coupling Allows Non-Integral Stoichiometries Of O2 Consumption And
ATP Synthesis
Don't worry about P/O ratios.
Assuming 3 H+ per ATP and G of -20 kJ/mol of H+, the calculated efficiency of the
ATPase would be: 32/(3 X 20) X 100 = 53%.
Accepted stoichiometries:
10 H+ pumped per NADH re-oxidized
6 H+ pumped per succinate oxidized
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