Chapter 7
Section 1 Glycolysis and Fermentation
Harvesting Chemical Energy
• Cellular respiration is the process by which cells break down
organic compounds to produce ATP.
• Both autotrophs and heterotrophs use cellular respiration to
make CO2 and water from organic compounds and O2.
• Cellular respiration can be divided into two stages: glycolysis
and aerobic respiration.
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Chapter 7
Section 1 Glycolysis and Fermentation
Photosynthesis-Cellular Respiration Cycle
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Chapter 7
Section 1 Glycolysis and Fermentation
Cellular Respiration
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Chapter 7
Section 1 Glycolysis and Fermentation
Glycolysis
• Cellular respiration begins with glycolysis, which
takes place in the cytosol of cells.
• During glycolysis, one six-carbon glucose molecule
is oxidized to form two three-carbon pyruvic acid
molecules.
• A net yield of two ATP molecules is produced for
every molecule of glucose that undergoes glycolysis.
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Chapter 7
Section 1 Glycolysis and Fermentation
Glycolysis
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Chapter 7
Section 1 Glycolysis and Fermentation
Glycolysis
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Chapter 7
Section 1 Glycolysis and Fermentation
Fermentation
• If oxygen is not present, some cells can convert
pyruvic acid into other compounds in the cytosol. The
combination of glycolysis and this process is
fermentation.
• Fermentation is also called Anaerobic respiration.
(without air)
• Fermentation produces NAD+, which allows for the
continued production of ATP through glycolysis.
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Chapter 7
Section 1 Glycolysis and Fermentation
Cellular Respiration Versus Fermentation
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Chapter 7
Section 1 Glycolysis and Fermentation
Fermentation, continued
• Lactic Acid Fermentation
– In lactic acid fermentation, an enzyme converts
pyruvic acid into another three-carbon compound,
called lactic acid.
– The buildup of lactic acid makes muscles feel
tired.
– Signal to rest and get more oxygen.
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Chapter 7
Section 1 Glycolysis and Fermentation
Fermentation
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Chapter 7
Section 1 Glycolysis and Fermentation
Fermentation, continued
• Alcoholic Fermentation
– Some organisms use a process called alcoholic
fermentation to convert pyruvic acid into ethyl
alcohol and CO2.
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Chapter 7
Section 1 Glycolysis and Fermentation
Two Types of
Fermentation
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Chapter 7
Section 1 Glycolysis and Fermentation
Comparing Aerobic and Anaerobic Respiration
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Chapter 7
Section 2 Aerobic Respiration
Overview of Aerobic Respiration
• Aerobic respiration occurs in the mitochondria and
only if oxygen is present.
• The Krebs cycle occurs in the mitochondria.
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Chapter 7
Section 2 Aerobic Respiration
The Krebs Cycle
• Pyruvic acid from glycolysis reacts to form acetyl CoA. Then,
acetyl CoA enters the Krebs cycle.
• Glucose completely broken down in the Krebs cycle.
• Krebs produces four CO2, two ATP, six NADH and two
FADH2 molecules (stored energy).
• The bulk of the energy still has not been transferred to ATP.
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Chapter 7
Section 2 Aerobic Respiration
Krebs Cycle
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Chapter 7
Section 2 Aerobic Respiration
Electron Transport Chain and Chemiosmosis
• Electrons from NADH and FADH2 are passed along the
electron transport chain in the mitochondrial membrane.
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Chapter 7
Section 2 Aerobic Respiration
Electron Transport Chain and
Chemiosmosis, continued
• Protons (hydrogen ions, H+) are also given up by NADH
and FADH2.
• As the electrons move through the electron transport
chain, they to pump protons into the space between the
inner and outer mitochondrial membranes.
• This results high concentration of protons.
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Chapter 7
Section 2 Aerobic Respiration
Electron Transport Chain and
Chemiosmosis, continued
• As protons move through ATP synthase ATP is produced.
• Oxygen combines with the electrons and protons to form
water.
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Chapter 7
Section 2 Aerobic Respiration
Electron Transport Chain and
Chemiosmosis, continued
• The Importance of Oxygen
– ATP can be synthesized by chemiosmosis only if
electrons continue to move along the electron transport
chain.
– Oxygen allows additional electrons to pass along the
chain.
– As a result, ATP can continue to be made through
chemiosmosis.
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Chapter 7
Section 2 Aerobic Respiration
Efficiency of Cellular Respiration
• Cellular respiration can produce up to 38 ATP
molecules from the oxidation of a single molecule of
glucose.
• Cellular respiration is nearly 20 times more efficient
than glycolysis alone.
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