Cellular respiration is the process by which cells break down glucose and other organic molecules to obtain energy in the form of ATP. It occurs in three main stages: glycolysis, the citric acid cycle, and oxidative phosphorylation. During glycolysis, glucose is broken down to form pyruvate in the cytoplasm. In the citric acid cycle, pyruvate enters the mitochondria and is further oxidized, producing NADH, FADH2, and ATP. During oxidative phosphorylation, electrons from NADH and FADH2 are passed through an electron transport chain in the mitochondrial inner membrane. Their energy is used to pump protons out of the matrix, establishing a proton gradient. ATP synthase uses this gradient to

2. BIOLOGICAL
OXIDATION

3. What is Cellular Respiration?What is Cellular Respiration?
The process by which chemical energy
in organic molecules is released by
oxidation
if it requires oxygen:
aerobic respiration
if it requires no oxygen:
anaerobic respiration

4. The process of CellularThe process of Cellular
Respiration is:Respiration is:
An Oxidation-Reduction Process
or REDOX Reaction
Gain of hydrogen atoms
Loss of hydrogen atoms
Glucose
Energy
Oxidation of GLUCOSEOxidation of GLUCOSE
Reduction O2
to H2
OReduction O2
to H2
O

5. Oxidation & ReductionOxidation & Reduction
Oxidation is losing electrons
Reduction is gaining electrons
Glucose gives off energy as it is oxidised
Gain of hydrogen atoms
Loss of hydrogen atoms
Glucose
Energy

6. BREATHING / VENTILATION
CELLULAR
RESPIRATION
Muscle cells carrying out
CO2
Bloodstream
Sugar + O2 → ATP + CO2 + H2O
O2

7. In Cellular RespirationIn Cellular Respiration
organic molecules are broken
down, bond by bond by a
series of enzyme-controlled
reactions

9. Bond
Bond energy,
kJ/mol
C–C 347
C=C 615
C≡C 812
C–O 360
C=O 728
C–H 414
H–H 436
H–O 464
O=O 498

10. Glucose Molecule
(carbohydrate)
C
C
C
C
C
CH
H
H
H
H
OH
OH
OH
OH
HO H
H O
C6H12O6
Substance:
Formula:
Energy: 17 kJ g-1

11. Amino AcidSubstance:
Energy: 17 kJ g-1

12. C
C
C
C
C
C
H
C
H
C
H
H
H
H
H
H
H
H
H
H
H
H
H
H
C
C
C
C
C
C
H
C
H
C
H
H
H
H
H
H
H
H
H
H
H
H
H
H
C
C
C
C
C
C
H
C
H
C
H
H
H
H
H
H
H
H
H
H
H
H
H
H
C CC O OO
O OO
C C
C
H
H
H
H
H
TriglycerideTriglyceride
Substance:
Energy:
37 kJ g-1

13. In Cellular Respiration:In Cellular Respiration:
 each reaction releases aeach reaction releases a smallsmall
amount of & is transferredamount of & is transferred
to :to :
- ATP- ATP
- lost aslost as heatheat

14. Energy released
from glucose
(as heat and light)
Burning glucose
in an experiment
100% About
40%
“Burning” glucose
in cellular respiration
Burning gasoline
in an auto engine
Gasoline energy
converted to
movement
25%
Energy released
from glucose
banked in ATP
How efficient is cell respiration?How efficient is cell respiration?

15. ATP:ATP: AAdenosinedenosine ttriripphosphatehosphate
The energy released during respiration is
not used directly by cells
Instead it is used to make a molecule
called ATP which stores the energy until
it is needed

16. Chemical Structure of ATPChemical Structure of ATP
3 Phosphates3 Phosphates
Ribose SugarRibose Sugar
Adenine BaseAdenine Base

17. musclemuscle
contractioncontraction
Some uses of ATPSome uses of ATP
germinationgermination
cell divisioncell division
chemical changeschemical changes
in cellsin cells
RespirationRespiration
suppliessupplies
the energy forthe energy for

18. Universal Energy CarrierUniversal Energy Carrier
Why ATP is called theWhy ATP is called the universaluniversal
energy carrierenergy carrier??
Found inFound in ALLALL organisms.organisms.

19. How is energy obtained fromHow is energy obtained from
ATP?ATP?
By breaking the
high- energy
bonds between
the last two
phosphates in
ATP

20. Hydrolysis of ATPHydrolysis of ATP
When ATP is hydrolysed,When ATP is hydrolysed, freefree
energyenergy (energy able to do work(energy able to do work
within the cell) is released.within the cell) is released.
This is anThis is an exergonic reactionexergonic reaction..
ATP + HATP + H22OO  ADP + PADP + Pii + free energy+ free energy

21. Hydrolysis needs an enzymeHydrolysis needs an enzyme
An EnzymeAn Enzyme

22. Respiration is exergonicRespiration is exergonic
Complete combustion of glucose is
highly exergonic
ATP is constantly being used and
remade

23. PHOSPHORYLATIONPHOSPHORYLATION

24. PhosphorylationPhosphorylation
As a result of respiration, energy isAs a result of respiration, energy is
released from the chemical bonds andreleased from the chemical bonds and
used for “phosphorylation” of ADP.used for “phosphorylation” of ADP.
PhosphorylationPhosphorylation is the process ofis the process of
adding a phosphate group to aadding a phosphate group to a
molecule…. By adding a phosphate ADPmolecule…. By adding a phosphate ADP
it becomes ATP.it becomes ATP.

25. PhosphorylationPhosphorylation
ADP may be rephosphorylated toADP may be rephosphorylated to
ATP inATP in THREETHREE ways:ways:
1.1.respiratory activityrespiratory activity
2.2.by another ‘high-energy’by another ‘high-energy’
compound, such ascompound, such as creatinecreatine
phosphatephosphate present in muscle cellspresent in muscle cells
3.3.photophosphorylationphotophosphorylation byby
chlorophyll-containing cells of greenchlorophyll-containing cells of green
plantsplants

26. 1. Respiratory Activity = ATP1. Respiratory Activity = ATP
Burning or metabolism of glucose:Burning or metabolism of glucose:
Glucose metabolism pathway trapsGlucose metabolism pathway traps
the free energy in ATP:the free energy in ATP:
ATPenergyfreePADP i →++
energyfreeOHCOOOHC ++→+ 2226126 666

27. 2. ATP from Creatine Phosphate2. ATP from Creatine Phosphate
• This system is extremely efficientThis system is extremely efficient
• It does not need oxygenIt does not need oxygen
• It leaves no waste productsIt leaves no waste products
WE ARE ONLY ABLE TO USE THIS FOR ABOUT 10-15WE ARE ONLY ABLE TO USE THIS FOR ABOUT 10-15
SECONDS BEFORE THIS SYSTEM RUNS OUT.SECONDS BEFORE THIS SYSTEM RUNS OUT.
HOWEVERHOWEVER
Creatine phosphateCreatine phosphate
is inside musclesis inside muscles

28. • RESPIRATORY SUBSTRATE

29. Fuels for Cellular RespirationFuels for Cellular Respiration
FuelsFuels: molecules whose stored energy: molecules whose stored energy
can be released for use.can be released for use.
The most common fuel in organismsThe most common fuel in organisms
isis glucoseglucose..
Other molecules are first convertedOther molecules are first converted
into glucose or other intermediateinto glucose or other intermediate
compounds.compounds.

30. Fuels are used in sequenceFuels are used in sequence
Glucose is stored here
as glycogen and is used
when the body is
working harder.
1. CARBOHYDRATES1. CARBOHYDRATES
2. FATS2. FATS
3. PROTEINS3. PROTEINS
Here some of the
glucose is stored as
glycogen and used to
maintain blood sugar
levels.
Liver
Muscle
Used when the
carbohydrates are
exhausted. Are
first converted to
glycerol and fatty
acids
Used when
carbohydrates
and fats have
been used up as
during prolonged
starvation

31. KEY REACTIONSKEY REACTIONS

32. Key ReactionsKey Reactions
Oxidation Decarboxylation
1. Adding oxygen
2. Removal of hydrogen
(dehydrogenation)
3. Removal of electrons
Removal of
carbon from a
compound to
make carbon
dioxide

33. What Carries the Electrons?What Carries the Electrons?
 NADNAD++
andand FADFAD++
are electron carriersare electron carriers
in redox reactionsin redox reactions
 twotwo forms:forms:
NADNAD++
/ FAD/ FAD++
(oxidised)(oxidised)
NADH + HNADH + H++
/ FADH/ FADH22 (reduced)(reduced)

34. What Carries the Electrons?What Carries the Electrons?
Gain or loss of electrons is often in the form of hydrogen.
The hydrogen is then passed to NAD+
or FAD+
Remember: glucose is oxidised as it loses hydrogen.

35. NADNAD++
(Nicotinamide Adenine
Dinucleotide:
 is derived from vitamin B
complex
acts as a coenzyme to
dehydrogenases by acting
as a hydrogen acceptor
++
+→+ HNADHHNAD 2
 needed in small amounts
in redox reactions
BindsBinds
looselyloosely
to theto the
enzymeenzyme

36. NADNAD++
acts as the energy carrieracts as the energy carrier
 NAD+
is reduced to NADH when it picks
up two electrons and one hydrogen ion

37. NADNAD++
accepts hydrogenaccepts hydrogen
NOTE:books use:
NADH;
NADH2;
reduced NAD
NADH+H+

38. All correct when saying that
NAD+
is:
 an energy carrier
 carries electrons
 carries hydrogen

39. FADFAD++
((FFlavinlavin AAdeninedenine DDinucleotide)inucleotide)
 derived from the vitamin riboflavin (B2)

40. FADFAD++
:: a prosthetic group of
succinate dehydrogenase
BindsBinds
ttighighttly toly to
thethe
enzymeenzyme

41. FADFAD++
is reduced to FADHis reduced to FADH22

42. Importance of FADHImportance of FADH22 & NADH& NADH22
Reducing power in NADHReducing power in NADH22 and FADHand FADH22 isis
used to form ATP by oxidativeused to form ATP by oxidative
phosphorylationphosphorylation

43. AN OVERVIEW OFAN OVERVIEW OF
CELL RESPIRATIONCELL RESPIRATION

44. General OutlineGeneral Outline
Glucose
CYTOSOL
Pyruvate
No O2 present
Fermentation
O2 present
Cellular respiration
Ethanol
or
lactate
Acetyl CoA
MITOCHONDRION
Citric
acid
cycle

45. If O2 is present, four pathways
operate:
1. Glycolysis
2. Transition reaction / Link reaction
3. Citric acid cycle / Krebs Cycle /
Tricarboxylic Acid Cycle (TCA)
4. Oxidative phosphorylation (uses
Electron transport chain /
Respiratory chain)

46. Location of the 4 phasesLocation of the 4 phases

47. Indicate where glycolysis, link reaction,Indicate where glycolysis, link reaction,
krebs cycle and the electron transport chainkrebs cycle and the electron transport chain
are located in this photo.are located in this photo.
Glycolysis
(anywhere in
cytoplasm)
Link reaction &
krebs cycle
(anywhere in matrix)
ETC
(anywhere on inner
membrane)

48. Glycolysis is Common for:Glycolysis is Common for:
Pyruvic AcidPyruvic AcidOxygen
Aerobic
No Oxygen
Anaerobic
Transition Reaction
Krebs Cycle
Electron Transport Chain
Fermentation
GlucoseGlucose
Glycolysis

49. Mitochondrion StructureMitochondrion Structure
Smooth outer
membrane
Folded inner membrane
Fold called
crista
Space inside cristae
called the matrix

50. Cristae provide a large SACristae provide a large SA
ATP synthase

51. The four phases of completeThe four phases of complete
glucose breakdownglucose breakdown

52. CITRIC ACID CYCLE /CITRIC ACID CYCLE /
KREBS CYCLE /KREBS CYCLE /
TRICARBOXYLIC ACIDTRICARBOXYLIC ACID
CYCLE (TCA)CYCLE (TCA)

53. Krebs Cycle:Krebs Cycle: Discovered by Sir Hans
Krebs in 1937
 cyclical metabolic pathway located in
the matrix of the mitochondria

54. Acetyl Co-AAcetyl Co-A joins a C4 molecule
oxaloacetate and C6 citrate results
Oxaloacetate
Citrate
Acetyl Co-A will
be oxidised to:
CoA
2 CO2
molecules
Coenzyme A:
 is removed in
the first reaction
can be reused
CoA

55. Citric Acid Cycle Uses Acetyl Co-ACitric Acid Cycle Uses Acetyl Co-A
to generate:
 2 ATP
 6 NADH
 2 FADH2
 4 CO2
Oxaloacetate
Citrate
starting
from
C6H12O6
starting
from
C6H12O6

56. 11
11
33
22
ONE acetyl-CoA PRODUCES
1 ATP per acetyl CoA
(substrate-level
phosphorylation)
1 ATP per acetyl CoA
(substrate-level
phosphorylation)

57. SummarySummary
As a result of one turn of the Krebs cycle the
cell makes:
1 FADH2
3 NADH
1 ATP
However, each glucose produces two pyruvic
acid molecules…. So the total outcome is:
2 FADH2
6 NADH
2 ATP

58. ELECTRON TRANSPORTELECTRON TRANSPORT
SYSTEM /SYSTEM /
ELECTRON TRANSPORTELECTRON TRANSPORT
CHAIN (ETC)CHAIN (ETC)

59. ETC is located in/on the cristaeETC is located in/on the cristae

60. What will happen to the electrons taken up
by NAD and FAD?
Electrons are carried along the ETC.
Why is this
important?
For ATP
production.

61. The Complete ETC consists of five units:
All are
proteins
except
ubiquinone /
coenzyme Q
which is a
lipid
Cytochrome c reductase
also called
bc1 complex

62. 4 protein complexes: I, II, III, IV
I - NADH-Q reductase
Q -Ubiquinone
Cc- Cytochrome c reductase
IV - Cytochrome c oxidase
MOBILE

63. ATP Synthesis by Oxidative PhosphorylationATP Synthesis by Oxidative Phosphorylation

64. Fig. 11 ATP formation by
chemiosmosis.
What will happen to the
electrons taken up by NAD and
FAD?
Electrons are carried along the
ETC.
Why is this important?
For ATP production.

65. ETC is linked to ATP productionETC is linked to ATP production
ETC
ETC
Oxygen receives
energy-spent electrons
at the end of the ETC

66. Energy is lost on moving downEnergy is lost on moving down
the ETCthe ETC

67. What is the use of the energy lost byWhat is the use of the energy lost by
electrons in the ETC?electrons in the ETC?
To pump HTo pump H++
from matrixfrom matrix
into intermembrane spaceinto intermembrane space

68. Why is it important to pump out HWhy is it important to pump out H++
??
To establish a
proton gradient
across the inner
membrane,
necessary for ATP
synthase to
generate ATP.

69. ATP SynthaseATP Synthase
Most protons move back to the matrix
through ATP synthase
ATP synthase is a membrane-bound
enzyme that uses the energy of the
proton gradient to synthesise ATP from
ADP + Pi

70. ATP SynthaseATP Synthase
 3 to 4 protons moving through ATP
synthase is enough to convert a
molecule of ADP and Pi into a molecule
of ATP
One ATP synthase
complex can generate
>100 molecules of
ATP each second

71. ATP SynthaseATP Synthase
In order to provide
energy to sustain our
lives, every day, each
one us produces a
quantity of ATP by
this mechanism that
is approximately
equal to our body
weights.

72. Representation of the ETCRepresentation of the ETC
 Electrons removed from NADH2 and FADH2 enter the
electron transport system
 First two carriers transport hydrogen, but the rest
(cytochromes) carry electrons
 A pair of electrons is carried by cytochromes
 Oxygen accepts electrons from NADH2 & NADH2
 Oxidising agent is molecular oxygen (O2)

73. ETCETC
A series of protein carriers (some are
cytochromes), pass electrons from one to the other
Inner
mitochondrial
membrane
Intermembrane
space
Mitochondrial
matrix
Electron
flow
ATP
SYNTHASE

74. Cytochromes are proteinsCytochromes are proteins
having an iron-containing group which carries
electrons

75. The Various CytochromesThe Various Cytochromes
Electrons pass
along:
-cytochrome b
-cytochrome c1
-cytochrome c
-cytochrome a + a3

76. Redox reactions

77. Respiration can be inhibitedRespiration can be inhibited
Cytochrome a3
:
-also called cytochrome
oxidase
- contains copper (Cu)
-passes electrons to oxygen
to form water
-this last stage can be inhibited by cyanide
or carbon monoxide

78. Cyanide poisoning in fish.

79. Cyanide is a:
non-competitive inhibitor of
cytochrome oxidase
CO is a:
competitive inhibitor of
cytochrome oxidase

80. Electron transport is coupled toElectron transport is coupled to
ATP formationATP formation
CYANIDE & CO stop respiration by
inhibiting flow of electrons along ETC

81. Suggest an explanation for the following
observation:
Cyanide is a quick-acting poison;
Cyanide is an inhibitor of the respiratory
chain thus NAD and FAD cannot be
regenerated. It blocks ATP formation.
Chemiosmosis cannot occur as
electrons no longer flow down the
electron transport chain.

83. Why does the electron transportWhy does the electron transport
chain have so many steps?chain have so many steps?
Too much free energy would be
released all at once—it could not be
harvested by the cell.
In a series of reactions, each releases
a small amount of energy that can be
captured by an endergonic reaction.

84. Summary

85. ETC occurs in steps to harvest ATPETC occurs in steps to harvest ATP
H2 + 1
/2 O2 2 H 1
/2 O2
(from food via NADH)
2 H+
+ 2 e–
2 H+
2 e–
H2O
1
/2 O2
Controlled
release of
energy for
synthesis of
ATP
ATP
ATP
ATP
Electrontransportchain
Freeenergy,G
(b) Cellular respiration(a) Uncontrolled reaction
Freeenergy,G
H2O
Explosive
release of
heat and light
energy
+

86. 1 NADH2 Yields 3 ATP
 accepts electrons from NADH2
 is the oxidising agent
O2 :

87. 1 FADH1 FADH22
yields 2 ATPyields 2 ATP

88. Cells are able to make ATP via:Cells are able to make ATP via:
substrate-level phosphorylation
– transferring a phosphate
directly to ADP from another
molecule
oxidative phosphorylation
– use of ATP synthase and
energy derived from a
proton (H+
) gradient to make
ATP
11
22

89. Oxidative Phosphorylation:Oxidative Phosphorylation:
ATP is synthesised as electron
carriers are reoxidised in the
presence of O2.
Two stages:
Electron transport chain
Chemiosmosis

90. ATP Synthesis by Oxidative PhosphorylationATP Synthesis by Oxidative Phosphorylation

91. Structure adapted to functionStructure adapted to function
Why is the inner membrane highly folded?
Provides a large surface area to
accommodate the ETC.

92. The ChemiosmoTiCThe ChemiosmoTiC
TheoryTheory

93. The Chemiosmotic TheoryThe Chemiosmotic Theory
Peter Mitchell (1961)
proposed the Chemiosmotic
Theory: the ETC energy is
used to move H+
(protons)
across the cristae
membrane, and
 that ATP is generated as the
H+
diffuse back into the matrix
through [proton motive force]

94. Once ATP is
formed, it
moves out of
the matrix to
be of use
inside the
cell.

95. FeelingFeeling
frustrated?frustrated?
That’sThat’s
normal!!normal!!