6 OXIDATIVE
PHOSPHORYLATION &
CHEMIOSMOSIS
Learning Objective

To understand the oxidative phosphorylation &
chemiosmosis
Success Criteria





outline the process of oxidative phosphorylation, with reference to
the roles of electron carriers, oxygen and the mitochondrial cristae;
outline the process of chemiosmosis, with reference to the electron
transport chain, proton gradients and ATPsynthase
state that oxygen is the final electron acceptor in aerobic
respiration;
evaluate the experimental evidence for the theory of chemiosmosis
explain why the theoretical maximum yield of ATP per molecule of
glucose is rarely, if ever, achieved in aerobic respiration;
Starter: Net Gain from 1 Glucose
ATP
Carbon Dioxide
Reduced NAD
Reduced FAD
How many of each one is produced during the following stages of
Aerobic Respiration?
GLYCOLYSIS
LINK REACTION
KREBS CYCLE
Starter Answers
ATP
Reduced NAD
Carbon Dioxide
Reduced FAD
How many of each one is produced during the following stages of
Aerobic Respiration?
GLYCOLYSIS
LINK REACTION
2 ATP
2 red NAD
KREBS CYCLE
2 ATP
2 red NAD
6 red NAD
2 Carbon Dioxide
4 Carbon Dioxide
2 red FAD
Key
 Cytoplasm
 Mitochondria
Glycolysis
Link Reaction
Krebs
Cycle
Electron Transport Chain
Summary so far!


Aerobic respiration makes 30 ATP per glucose
Aerobic respiration makes 30 ATP
2
ATP come from glycolysis
 2 ATP from Krebs Cycle
So where does the rest of the energy
come from?
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
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Where does the remaining 26 ATP come from?
The Electron Transport Chain!
The ETC makes ATP from the reduced NAD and
Reduced FAD made in the earlier stages.
The 10 red NAD make 26 ATP molecules
Oxidative Phosphorylation


Oxidative Phosphorylation is the formation of ATP
by adding a phosphate to ADP in the presence of
oxygen (the final electron acceptor)
Happens on the cristae, with molecules moving
between the matrix and the intermembrane space
Outline
1.
2.
3.
4.
5.
6.
Red NAD releases 2 H ions and 2 electrons (along ETC)
Red FAD releases 2 H ions (to join with ½ oxygen) and 2
electrons (along ETC)
Complex III & IV pump H ions into the intermembrance
space
High concentration of H ions in the intermembrane space
means they move by chemiosmosis through ATP synthase
ATP synthase uses the motive force to turn ADP back into
ATP
½ Oxygen accepts the 2 H ions from red FAD and 4
electrons from the end of the ETC
NAD
NAD
Matrix
H
FAD
H
eH+
Inter
membrane
space
H
H+
H+
H+
Pi
ADP
e-
Electron carriers
H+
H+
H+
H+
H+
ATP Synthase
NAD
Matrix
H
eH+
Inter
membrane
space
H+
H+
H+
H+
ADP
e-
H+
H+
H+
Pi
H+
NAD
Matrix
H
H+
H+
H
H
ee-
Inter
membrane
space
H+
H+
H+
H+
H+
H+
H+
Pi
ADP
NAD
Matrix
H
Pi
H
Inter
membrane
space
H+
H+
H+
H+
H+
H+
H
H+
ADP
ATP
Outline
1.
2.
3.
4.
5.
6.
Net Gain:
• 10 red NAD = 26 ATP
Red NAD releases 2 H ions and 2 electrons (along ETC)
Red FAD releases 2 H ions (to join with ½ oxygen) and 2
electrons (along ETC)
Complex III & IV pump H ions into the intermembrance
space
High concentration of H ions in the intermembrane space
are pumped through ATP synthase (chemiosmosis)
ATP synthase uses the motive force to turn ADP back into
ATP
Oxygen accepts the 4 H ions from 2 red FAD and 4
electrons from the end of the ETC
Task

Model Oxidative Phosphorylation
Summary
Summary
Aerobic Respiration Overview
However why is this not always the case?
•
•
•
Proton leak across mitochondrial space
ATP produced may actively transport pyruvate
into mitochondria
Moves reduced NAD from cytoplasm made
during Glycolysis into mitochondria
PPQ

Complete legacy paper questions
Markscheme
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See end of word doc