8.2 Cell Respiration (AHL)
Essential idea: Energy is
converted to a usable form
in cell respiration.
ATP is made most commonly
oxidative phosphorylation is used.
The key component in this process
is ATP synthase (below). This
enzyme sits embedded within the
inner membrane of mitochondria.
When hydrogen ions flow through
ATP synthase the motive force is
used to convert ADP and
phosphate into ATP.
Adenosine triphosphate (ATP) is the energy currency of cells. It is
unstable and will breakdown into Adenosine diphosphate (ADP)
and a phosphate releasing energy (as heat). The energy released by
ATP is held in the bond between the second and the third
phosphates. ATP can therefore be used as a coenzyme in many
parts of the cells metabolism providing the energy needed for
many reactions. Because of it's unstable nature it is only produced
when needed. The purpose of cell respiration therefore it to
breakdown carbohydrates and lipids so that ATP can be produced.
By Chris Paine
http://www.ks.uiuc.edu/Research/f0atpase/overview.jpg
http://wiki.chemprime.chemeddl.org/images/7/7d/ATP_ADP.gif
https://bioknowledgy.weebly.com/
Understandings
Statement
8.2.U1
Guidance
Cell respiration involves the oxidation and reduction of
electron carriers.
8.2.U2 Phosphorylation of molecules makes them less stable.
8.2.U3 In glycolysis, glucose is converted to pyruvate in the
The names of the intermediate compounds in
cytoplasm.
gylcolysis is not required.
8.2.U4 Glycolysis gives a small net gain of ATP without the
The names of the intermediate compounds in
use of oxygen.
gylcolysis is not required.
8.2.U5 In aerobic cell respiration pyruvate is decarboxylated
and oxidized, and converted into acetyl compound and
attached to coenzyme A to form acetyl coenzyme A in
the link reaction.
8.2.U6 In the Krebs cycle, the oxidation of acetyl groups is
The names of the intermediate compounds in the
coupled to the reduction of hydrogen carriers, liberating Krebs cycle is not required.
carbon dioxide.
8.2.U7 Energy released by oxidation reactions is carried to the
cristae of the mitochondria by reduced NAD and FAD.
8.2.U8 Transfer of electrons between carriers in the electron
transport chain in the membrane of the cristae is
coupled to proton pumping.
8.2.U9 In chemiosmosis protons diffuse through ATP synthase
to generate ATP.
8.2.U10 Oxygen is needed to bind with the free protons to
maintain the hydrogen gradient, resulting in the
formation of water.
8.2.U11 The structure of the mitochondrion is adapted to the
function it performs.
Applications and Skills
8.2.A1
8.2.S1
8.2.S2
Statement
Electron tomography used to produce images of
active mitochondria.
Analysis of diagrams of the pathways of aerobic
respiration to deduce where decarboxylation and
oxidation reactions occur.
Annotation of a diagram of a mitochondrion to
indicate the adaptations to its function.
Guidance
chemiosmosis
Respiration consists of several different
interlinked metabolic pathways.
chemiosmosis
Respiration consists of several different
interlinked metabolic pathways.
8.2.U11 The structure of the mitochondrion is adapted to the function it performs.
8.2.S2 Annotation of a diagram of a mitochondrion to indicate the adaptations to its function.
8.2.U11 The structure of the mitochondrion is adapted to the function it performs.
8.2.S2 Annotation of a diagram of a mitochondrion to indicate the adaptations to its function.
Label the structures:
http://commons.wikimedia.org/wiki/File:Animal_mitochondrion_diagram_en.svg
8.2.U11 The structure of the mitochondrion is adapted to the function it performs.
8.2.S2 Annotation of a diagram of a mitochondrion to indicate the adaptations to its function.
Label the structures:
matrix
Inter-membrane space
cristae
ribosomes
inner membrane
outer membrane
naked loops of DNA
http://commons.wikimedia.org/wiki/File:Animal_mitochondrion_diagram_en.svg
8.2.U11 The structure of the mitochondrion is adapted to the function it performs.
8.2.S2 Annotation of a diagram of a mitochondrion to indicate the adaptations to its function.
8.2.U11 The structure of the mitochondrion is adapted to the function it performs.
8.2.S2 Annotation of a diagram of a mitochondrion to indicate the adaptations to its function.
8.2.A1 Electron tomography used to produce images of active mitochondria.
Electron tomography is a technique for obtaining 3D structures
of sub-cellular structures using electron micrographs.
Electron tomography is improving the understanding
of mitochondria structure and function.
Use the link to find out
more:http://www.sci.sdsu.edu/TFrey/MitoMovie.htm
8.2.U1 Cell respiration involves the oxidation and reduction of electron carriers.
What is oxidation?
8.2.U1 Cell respiration involves the oxidation and reduction of electron carriers.
What is oxidation?
8.2.U1 Cell respiration involves the oxidation and reduction of electron carriers.
What is oxidation?
8.2.U1 Cell respiration involves the oxidation and reduction of electron carriers.
Who are the electron carries in cell respiration?
The most common hydrogen carrier is NAD
(Nicotinamide Adenine Dinucleotide)
NAD+ + 2H+ + 2e-
reduction
NADH + H+
oxidation
Use the simplified form of the equation omitting
the detail of the H+ ions and electrons:
NAD+
reduction
oxidation
NADH + H+
8.2.U1 Cell respiration involves the oxidation and reduction of electron carriers.
Who are the electron carries in cell respiration?
Another less frequently used hydrogen carrier is
FAD (Flavin Adenine Dinucleotide).
FAD + 2H+ + 2e-
reduction
FADH2
oxidation
Use the simplified form of the equation omitting
the detail of the H+ ions and electrons:
FAD
reduction
oxidation
FADH2
glycolysis
chemiosmosis
Respiration consists of several different
interlinked metabolic pathways.
8.2.U3 In glycolysis, glucose is converted to pyruvate in the cytoplasm.
8.2.U4 Glycolysis gives a small net gain of ATP without the use of oxygen.
Glycolysis is the splitting of glucose into pyruvate
Use the animations to learn about the
process of glycolysis
http://www.science.smith.edu/departments/Biology/Bio231/gl
ycolysis.html
http://highered.mheducation.com/sites/0072507470/student_
view0/chapter25/animation__how_glycolysis_works.html
8.2.U3 In glycolysis, glucose is converted to pyruvate in the cytoplasm.
8.2.U4 Glycolysis gives a small net gain of ATP without the use of oxygen.
Glycolysis is the splitting of glucose into pyruvate
by substrate-level phosphorylation.
8.2.U2 Phosphorylation of molecules makes them less stable.
Phosphorylation is a reaction where a phosphate group (PO43-) is added to an organic
molecule
The phosphorylated
molecule is less stable
and therefore reacts
more easily in the
metabolic pathway.
The phosphate group is
usually transferred from ATP
Reactions that would otherwise proceed slowly and require energy into a reaction that
happens quickly releasing energy.
http://commons.wikimedia.org/wiki/File:Glycolysis2.svg
8.2.U3 In glycolysis, glucose is converted to pyruvate in the cytoplasm.
8.2.U4 Glycolysis gives a small net gain of ATP without the use of oxygen.
Glycolysis is the splitting of glucose into pyruvate
In Summary:
•
•
•
•
•
•
•
Glycolysis occurs in cytoplasm
A hexose sugar (e.g. glucose) is phosphorylated using ATP
The hexose phosphate is then split into two triose phosphates
Oxidation occurs removing hydrogen
The hydrogen is used to reduce NAD to NADH
Four ATP are produced resulting in a net gain of two ATP
Two pyruvate molecules are produced at the end of glycolysis
http://en.wikipedia.org/wiki/Glycolysis
link reaction
chemiosmosis
Respiration consists of several different
interlinked metabolic pathways.
8.2.U5 In aerobic cell respiration pyruvate is decarboxylated and oxidized, and converted into acetyl
compound and attached to coenzyme A to form acetyl coenzyme A in the link reaction.
8.2.U5 In aerobic cell respiration pyruvate is decarboxylated and oxidized, and converted into acetyl
compound and attached to coenzyme A to form acetyl coenzyme A in the link reaction.
8.2.U5 In aerobic cell respiration pyruvate is decarboxylated and oxidized, and converted into acetyl
compound and attached to coenzyme A to form acetyl coenzyme A in the link reaction.
8.2.U5 In aerobic cell respiration pyruvate is decarboxylated and oxidized, and converted into acetyl
compound and attached to coenzyme A to form acetyl coenzyme A in the link reaction.
8.2.U5 In aerobic cell respiration pyruvate is decarboxylated and oxidized, and converted into acetyl
compound and attached to coenzyme A to form acetyl coenzyme A in the link reaction.
8.2.U5 In aerobic cell respiration pyruvate is decarboxylated and oxidized, and converted into acetyl
compound and attached to coenzyme A to form acetyl coenzyme A in the link reaction.
In Summary:
•
•
•
•
•
•
•
•
pyruvate (from glycolysis) enters the mitochondrion matrix
enzymes remove one carbon dioxide and hydrogen from the pyruvate
hydrogen is accepted by NAD to form NADH
removal of hydrogen is oxidation
removal of carbon dioxide is decarboxylation
the link reaction is therefore oxidative decarboxylation
the product is an acetyl group which reacts with coenzyme A
acetyl CoA enters Krebs cycle
Glycolysis is not needed, but the reaction is slower.
Kreb’s cycle
chemiosmosis
8.2.U6 In the Krebs cycle, the oxidation of acetyl groups is coupled to the reduction of hydrogen
carriers, liberating carbon
Krebs cycle reduces electron carriers in
preparation for oxidative phosphorylation
Use the animations to learn about Krebs
cycle
(carbon is released as CO2 as a by-product)
http://faculty.nl.edu/jste/aerobic_respirat
ion.htm#Citric%20acid%20%28CA%29%2
0cycle
http://www.wiley.com/legacy/college/boyer/047
0003790/animations/tca/tca.htm
http://highered.mheducation.com/olcweb/cgi/pluginpop
.cgi?it=swf::525::530::/sites/dl/free/0072464631/291136
/krebsCycle.swf::krebsCycle.swf
http://www.wiley.com/college/pratt/0471393878/stu
dent/animations/citric_acid_cycle/index.html
8.2.U6 In the Krebs cycle, the oxidation of acetyl groups is coupled to the reduction of hydrogen
carriers, liberating carbon dioxide.
8.2.U6 In the Krebs cycle, the oxidation of acetyl groups is coupled to the reduction of hydrogen
carriers, liberating carbon dioxide.
8.2.U6 In the Krebs cycle, the oxidation of acetyl groups is coupled to the reduction of hydrogen
carriers, liberating carbon dioxide.
8.2.U6 In the Krebs cycle, the oxidation of acetyl groups is coupled to the reduction of hydrogen
carriers, liberating carbon dioxide.
H+
8.2.U6 In the Krebs cycle, the oxidation of acetyl groups is coupled to the reduction of hydrogen
carriers, liberating carbon dioxide.
NADH H+
8.2.U6 In the Krebs cycle, the oxidation of acetyl groups is coupled to the reduction of hydrogen
carriers, liberating carbon dioxide.
8.2.U6 In the Krebs cycle, the oxidation of acetyl groups is coupled to the reduction of hydrogen
carriers, liberating carbon dioxide.
8.2.U6 In the Krebs cycle, the oxidation of acetyl groups is coupled to the reduction of hydrogen
carriers, liberating carbon dioxide.
8.2.U6 In the Krebs cycle, the oxidation of acetyl groups is coupled to the reduction of hydrogen
carriers, liberating carbon dioxide.
8.2.U7 Energy released by oxidation reactions is carried to the cristae of the mitochondria by
reduced NAD and FAD.
The reduced forms of NAD and FAD
carry H+ ions and electrons to the
electron transport chain, is which is
situated in the folds on the inner
membrane, i.e. the cristae.
8.2.U6 In the Krebs cycle, the oxidation of acetyl groups is coupled to the reduction of hydrogen
carriers, liberating carbon dioxide.
In Summary:
• acetyl CoA enters the Krebs cycle
• acetyl group (2C) joins a 4C sugar to form a 6C sugar
• oxidative decarboxylation of the 6C sugar to a 5C compound produces
CO2
• oxidative decarboxylation of the 5C compound to a 4C compound
produces CO2
• The process is oxidative as NAD and FAD are reduced by the addition of
hydrogen
• two CO2 are produced per molecule of pyruvate / cycle
• along with three NADH + H+ and one FADH2 per molecule of pyruvate /
cycle
• one ATP is produced by substrate level phosphorylation (from ADP + Pi)
per molecule of pyruvate / cycle
• NADH and FADH2 provide electrons to the electron transport chain
electron
transport
chain
chemiosmosis
8.2.U8 Transfer of electrons between carriers in the electron transport chain in the membrane of the
cristae is coupled to proton pumping.
Oxidative phosphorylation part I:
electron transport chain (ETC)
The process of oxidative
phosphorylation happens
across the inner membrane
A series of integral protein
complexes act as electron carriers
forming the electron transport chain
8.2.U8 Transfer of electrons between carriers in the electron transport chain in the membrane of the
cristae is coupled to proton pumping.
Oxidative phosphorylation part I:
electron transport chain (ETC)
8.2.U8 Transfer of electrons between carriers in the electron transport chain in the membrane of the
cristae is coupled to proton pumping.
Oxidative phosphorylation part I:
electron transport chain (ETC)
8.2.U8 Transfer of electrons between carriers in the electron transport chain in the membrane of the
cristae is coupled to proton pumping.
Oxidative phosphorylation part I:
electron transport chain (ETC)
8.2.U8 Transfer of electrons between carriers in the electron transport chain in the membrane of the
cristae is coupled to proton pumping.
Oxidative phosphorylation part I:
electron transport chain (ETC)
chemiosmosis
8.2.U9 In chemiosmosis protons diffuse through ATP synthase to generate ATP.
8.2.U9 In chemiosmosis protons diffuse through ATP synthase to generate ATP.
8.2.U9 In chemiosmosis protons diffuse through ATP synthase to generate ATP.
Oxidative phosphorylation part II:
chemiosmosis
8.2.U9 In chemiosmosis protons diffuse through ATP synthase to generate ATP.
Oxidative phosphorylation part II:
chemiosmosis
This creates an electrochemical
gradient.
The yield of ATP from
chemiosmosis is potentially 32
molecules, but in most conditions
the yield is slightly lower.
Nature of Science: Paradigm shift—the chemiosmotic theory led to a paradigm
shift in the field of bioenergetics. (2.3)
In 1961 Peter Mitchell proposed the chemiosmotic theory.
His ideas explained how synthesis is coupled to
electron transport and proton movement.
His ideas were very different to previous explanations.
It takes time for scientists working in a field to accept
paradigm shifts, even when there is strong evidence.
After many years the theory was accepted. Peter Mitchell
received the Nobel Prize for Chemistry in 1978
Find out more:
http://biologyjunction.com/chemiosmotic_theory.htm
http://www.nobelprize.org/nobel_prizes/chemistry/la
ureates/1978/press.html
8.2.U10 Oxygen is needed to bind with the free protons to maintain the hydrogen gradient, resulting
in the formation of water.
Oxidative phosphorylation part I:
electron transport chain (ETC)
8.2.U10 Oxygen is needed to bind with the free protons to maintain the hydrogen gradient, resulting
in the formation of water.
Oxidative phosphorylation part I:
electron transport chain (ETC)
A summary of oxidative phosphorylation (8.2.U8 – 8.2.U10)
Use the animations to learn to check your
understanding of oxidative phosphorylation.
http://faculty.nl.edu/jste/electron_transport_system.htm
http://highered.mheducation.com/olcweb/cgi/pluginpop.cgi?it
=swf::535::535::/sites/dl/free/0072437316/120071/bio11.swf::
Electron%20Transport%20System%20and%20ATP%20Synthesis
http://www.wiley.com/legacy/college/boyer/0470003790
/animations/electron_transport/electron_transport.htm
http://commons.wikimedia.org/wiki/File:2508_The_Electron_Transport_Chain.jpg
A summary of oxidative phosphorylation (8.2.U8 – 8.2.U10)
http://commons.wikimedia.org/wiki/File:2508_The_Electron_Transport_Chain.jpg
A summary of oxidative phosphorylation (8.2.U8 – 8.2.U10)
• the electron transport chain is situated on the inner mitochondrial
membrane
• hydrogen is transferred to the electron transport chain by hydrogen carriers,
i.e. NADH and FADH2
• The hydrogen carriers release electrons which are transferred between
carriers this releases energy …
• …. which is used to pump H+ ions (from the matrix) across inner membrane
• H+ ions to accumulate in the inter-membrane space creating a concentration
gradient
• H+ ions return to the matrix through ATP synthase
• Down the electrochemical concentration gradient
• This produces ATP by chemiosmosis
• oxygen is the final electron acceptor for the electron transport chain
• oxygen combines with electrons and H+ ions to produce water
http://commons.wikimedia.org/wiki/File:2508_The_Electron_Transport_Chain.jpg
8.2.S1 Analysis of diagrams of the pathways of aerobic respiration to deduce where
decarboxylation and oxidation reactions occur.
1. Indicate two places where
decarboxylation occurs. (1)
2. Explain why the given places where
selected. (1)
8.2.S1 Analysis of diagrams of the pathways of aerobic respiration to deduce where
decarboxylation and oxidation reactions occur.
1. Indicate two places where
decarboxylation occurs. (1)
2. Explain why the given places where
selected. (1)
decarboxylation
The molecule reduces the number of
carbon atoms it contains in each
place, therefore each reaction must
be a decarboxylation.
decarboxylation
decarboxylation
8.2.S1 Analysis of diagrams of the pathways of aerobic respiration to deduce where
decarboxylation and oxidation reactions occur.
3. The diagram shows the three stages of glycolysis.
Which processes are indicated by I, II and III?
I
II
III
A Lysis
Phosphorylation
Oxidation and ATP
formation
B Oxidation and
Phosphorylation
Lysis
C Phosphorylation
Lysis
Oxidation and ATP
formation
D Phosphorylation
Oxidation and
ATP formation
Lysis
ATP formation
8.2.S1 Analysis of diagrams of the pathways of aerobic respiration to deduce where
decarboxylation and oxidation reactions occur.
3. The diagram shows the three stages of glycolysis.
Which processes are indicated by I, II and III?
I
II
III
A Lysis
Phosphorylation
Oxidation and ATP
formation
B Oxidation and
Phosphorylation
Lysis
C Phosphorylation
Lysis
Oxidation and ATP
formation
D Phosphorylation
Oxidation and
ATP formation
Lysis
ATP formation
8.2.U11 The structure of the mitochondrion is adapted to the function it performs.
8.2.S2 Annotation of a diagram of a mitochondrion to indicate the adaptations to its function.
Annotate the labelled structures:
matrix
Inter-membrane space
cristae
ribosomes
inner membrane
outer membrane
naked loops of DNA
http://commons.wikimedia.org/wiki/File:Animal_mitochondrion_diagram_en.svg
8.2.U11 The structure of the mitochondrion is adapted to the function it performs.
8.2.S2 Annotation of a diagram of a mitochondrion to indicate the adaptations to its function.
Annotate the labelled structures:
matrix
fluid containing enzymes  for the
Krebs cycle and the link reaction.
Inter-membrane space
Small space  H+ ions pumped
into the space quickly generate a
high concentration gradient for
chemiosmosis.
Folds in the innner
membrane  increase cristae
surface area available for
oxidative phosphorylation
ribosomes
inner membrane
Synthesises proteins,
including enzymes
used in aerobic
respiration.
naked loops of DNA
Necessary mitochondria
function, including
protein synthesis
outer membrane
contains the contents of the
mitochondrion  enables optimal
conditions for aerobic respiration
contains the integral
proteins that make up the
electron transport chain
and ATP synthase 
electron transport and
chemiosmosis
http://commons.wikimedia.org/wiki/File:Animal_mitochondrion_diagram_en.svg