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Cellular Respiration
Introduction
 Before food can be used to perform
work, its energy must be released
through the process of respiration.
 Two main types of respiration exist in
living things. Both begin with glycolysis.
 Glycolysis: a process by which one glucose
molecule is broken down into two pyruvic
acid molecules.
 Fermentation (anaerobic respiration): pyruvic
acid is broken down without the use of
oxygen
 Oxidative Respiration (aerobic respiration):
pyruvic acid is metabolized using oxygen
Aerobic Respiration
Glucose
Glycolysis
Krebs
cycle
Fermentation (without
oxygen)
Electron
transport
Alcohol or
lactic acid
Anaerobic Respiration
Glycolysis
Glycolysis
 Glycolysis occurs in the cytoplasm.
 It does not require oxygen.
 Each of its four stages is catalyzed by a
specific enzyme.
Glycolysis
ATP
ATP
Glucose
ADP + P
PGAL
ADP + P
PGAL
NAD+ +
2 H+ + 2 e-
NAD+ +
2 H+ + 2 e-
NADH + H+
NADH + H+
PGAL + P
2 ADP + 2 P
2 ATP
Pyruvic Acid
PGAL + P
2 ADP + 2 P
2 ATP
Pyruvic Acid
Anaerobic Respiration
Fermentation
Fermentation
(Anaerobic Respiration)
 Fermentation is the breakdown of pyruvic
acid without the use of oxygen.
 Glycolysis + Fermentation = Anaerobic
Respiration
 The metabolism of pyruvic acid
during fermentation does not
produce any ATP. Instead, the
function of fermentation is to break
down pyruvic acid and regenerate
NAD+ for reuse in glycolysis.
To Glycolysis
Lactic Acid Fermentation
NADH + H+
NAD+ + 2 H+ + 2 e-
Pyruvic Acid
Lactic Acid
Alcoholic Fermentation
NADH + H+
NAD+ + 2 H+ + 2 e-
Pyruvic Acid
CO2
Ethyl
Alcohol
(Ethanol)
Aerobic Respiration
Oxidative Respiration
Aerobic Respiration
 The result of glycolysis and aerobic respiration is
shown by the reaction:
 C6H12O6 + 6 O2 → 6 H2O + 6 CO2 + 38 ATP
 Aerobic respiration occurs in the mitochondria
 outer and inner membrane
 matrix: dense solution enclosed by inner membrane
 cristae: the folds of the inner membrane that house
the electron transport chain and ATP synthase
 Steps:
 Conversion of Pyruvic Acid
 Kreb’s Cycle
 Electron Transport Chain
Structure of Mitochondrion
Kreb’s Cycle
 The Krebs Cycle is
the central
biochemical pathway
of aerobic
respiration. It is
named after its
discoverer, Sir Hans
Krebs. Because
citric acid is formed
in the process, it is
also known as the
Citric Acid Cycle.
Conversion of PA
Kreb’s Cycle
Pyruvic
Acid
NAD+
NADH + H+
C C
Acetyl-CoA
CoA
C C C
CO2
CoA
C
C C C C
C C C C C C
Citric Acid
Oxaloacetic
Acid
NAD+
NADH + H+
NADH + H+
C
CO2
NAD+
C C C C
Ketoglutaric C C C C C
Acid
NAD+
Malic
Acid
FADH2
FAD
Succinic
Acid
C C C C
NADH + H+
ADP
ATP
+P
CO2
C
Electron Transport Chain
 Glycolysis, the conversion of PA to acetylCoA, and the Krebs Cycle complete the
breakdown of glucose.
 Up to this point:
 4 ATP (2 from glycolysis, 2 from Krebs)
 10 NADH + H+ (2 from glycolysis, 2 from the
conversion of PA, 6 from Krebs)
 2 FADH2 (from Krebs)
Electron Transport Chain
 NADH + H+ and FADH2 carry electrons to
an electron transport chain, where
additional ATP is produced.
 10 NADH
30 ATP
 2 FADH2
4 ATP
Electron Transport Chain
Intermembrane Space
Inner Membrane
Matrix
NADH + H+
FADH2
NAD+
FAD
Intermembrane Space
Inner Membrane
Matrix
NADH + H+
FADH2
NAD+
FAD
Intermembrane Space
Inner Membrane
Matrix
NADH + H+
FADH2
NAD+
FAD
Intermembrane Space
Inner Membrane
Matrix
NADH + H+
FADH2
NAD+
FAD
Intermembrane Space
Inner Membrane
Matrix
NADH + H+
FADH2
NAD+
FAD
Intermembrane Space
Inner Membrane
Matrix
NADH + H+
FADH2
NAD+
FAD
Intermembrane Space
Inner Membrane
Matrix
NADH + H+
FADH2
NAD+
FAD
Intermembrane Space
Inner Membrane
Matrix
NADH + H+
FADH2
NAD+
FAD
Intermembrane Space
Inner Membrane
Matrix
NADH + H+
FADH2
NAD+
FAD
Intermembrane Space
Inner Membrane
Matrix
NADH + H+
FADH2
NAD+
FAD
Intermembrane Space
Inner Membrane
Matrix
NADH + H+
FADH2
NAD+
FAD
Intermembrane Space
Inner Membrane
Matrix
NADH + H+
FADH2
NAD+
FAD
Intermembrane Space
Inner Membrane
Matrix
NADH + H+
FADH2
NAD+
FAD
Intermembrane Space
Inner Membrane
Matrix
NADH + H+
FADH2
NAD+
FAD
Intermembrane Space
Inner Membrane
Matrix
NADH + H+
FADH2
NAD+
FAD
Intermembrane Space
Inner Membrane
Matrix
NADH + H+
FADH2
NAD+
FAD
Intermembrane Space
Inner Membrane
Matrix
NADH + H+
FADH2
NAD+
FAD
Intermembrane Space
Inner Membrane
Matrix
NADH + H+
FADH2
NAD+
FAD
Intermembrane Space
Inner Membrane
Matrix
NADH + H+
FADH2
NAD+
FAD
Intermembrane Space
Inner Membrane
Matrix
NADH + H+
FADH2
NAD+
FAD
Intermembrane Space
Inner Membrane
Matrix
NADH + H+
FADH2
NAD+
FAD
Intermembrane Space
Inner Membrane
Matrix
NADH + H+
FADH2
NAD+
FAD
Intermembrane Space
Inner Membrane
Matrix
NADH + H+
FADH2
NAD+
FAD
Intermembrane Space
Inner Membrane
Matrix
~
e
NADH + H+
FADH2
NAD+
FAD
ADP + P
ATP
Electron Transport
Hydrogen Ion Movement
Channel
Intermembrane
Space
ATP synthase
Inner
Membrane
Matrix
ATP Production
Energy Yield
Energy Yield
 Aerobic respiration produces a maximum
of 38 ATP.
 2 ATP from Glycolysis
 2 ATP from Krebs
 34 ATP from ETC
 Reasons why ATP yield can be less than
38:
 Sometimes energy is required to transport
NADH + H+ formed by glycolysis from the
cytoplasm through the inner mitochondrial
membrane.
 Some H+ in chemiosmosis may leak through
the membrane.
Energy Yield
Energy Yield
 Aerobic Respiration is generally 19 times
more efficient than anaerobic respiration.
 The ATP produced during aerobic
respiration represents about 1/2 of the
energy stored in a molecule of glucose.