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Copyright © by Holt, Rinehart and Winston. All rights reserved.
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Chapter Presentation
Transparencies
Visual Concepts
Standardized Test Prep
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Chapter 7
Cellular Respiration
Table of Contents
Section 1 Glycolysis and Fermentation
Section 2 Aerobic Respiration
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Chapter 7
Objectives
• Identify the two major steps of cellular respiration.
• Describe the major events in glycolysis.
• Compare lactic acid fermentation with alcoholic
fermentation.
• Calculate the efficiency of glycolysis.
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Chapter 7
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.
• The products of cellular respiration are the reactants in
photosynthesis; conversely, the products of photosynthesis are
reactants in cellular respiration.
• Cellular respiration can be divided into two stages: glycolysis
and aerobic respiration.
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Chapter 7
Photosynthesis-Cellular Respiration Cycle
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Chapter 7
Cellular Respiration
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Chapter 7
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
Glycolysis
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Chapter 7
Glycolysis
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Chapter 7
Fermentation
• If oxygen is not present, some cells can convert
pyruvic acid into other compounds through additional
biochemical pathways that occur in the cytosol. The
combination of glycolysis and these additional
pathways is fermentation.
• Fermentation does not produce ATP, but it does
regenerate NAD+, which allows for the continued
production of ATP through glycolysis.
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Chapter 7
Cellular Respiration Versus Fermentation
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Chapter 7
Fermentation, continued
• Lactic Acid Fermentation
– In lactic acid fermentation, an enzyme converts
pyruvic acid into another three-carbon compound,
called lactic acid.
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Chapter 7
Fermentation
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Chapter 7
Fermentation, continued
• Alcoholic Fermentation
– Some plants and unicellular organisms, such as
yeast, use a process called alcoholic
fermentation to convert pyruvic acid into ethyl
alcohol and CO2.
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Chapter 7
Two Types of
Fermentation
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Chapter 7
Comparing Aerobic and Anaerobic Respiration
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Chapter 7
Efficiency of Glycolysis
• Through glycolysis, only about 2 percent of the
energy available from the oxidation of glucose is
captured as ATP.
• Much of the energy originally contained in glucose is
still held in pyruvic acid.
• Glycolysis alone or as part of fermentation is not very
efficient at transferring energy from glucose to ATP.
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Chapter 7
Objectives
• Relate aerobic respiration to the structure of a mitochondrion.
• Summarize the events of the Krebs cycle.
• Summarize the events of the electron transport chain and
chemiosmosis.
• Calculate the efficiency of aerobic respiration.
• Contrast the roles of glycolysis and aerobic respiration in
cellular respiration.
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Chapter 7
Overview of Aerobic Respiration
• In eukaryotic cells, the processes of aerobic
respiration occur in the mitochondria. Aerobic
respiration only occurs if oxygen is present in the cell.
• The Krebs cycle occurs in the mitochondrial matrix.
The electron transport chain (which is associated with
chemiosmosis) is located in the inner membrane.
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Chapter 7
The Krebs Cycle
• In the mitochondrial matrix, pyruvic acid produced in
glycolysis reacts with coenzyme A to form acetyl CoA. Then,
acetyl CoA enters the Krebs cycle.
• One glucose molecule is completely broken down in two
turns of the Krebs cycle. These two turns produce four CO2
molecules, two ATP molecules, and hydrogen atoms that are
used to make six NADH and two FADH2 molecules.
• The bulk of the energy released by the oxidation of glucose
still has not been transferred to ATP.
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Chapter 7
Krebs Cycle
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Chapter 7
Electron Transport Chain and Chemiosmosis
• High-energy electrons in hydrogen atoms from NADH and
FADH2 are passed from molecule to molecule in the electron
transport chain along the inner mitochondrial membrane.
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Chapter 7
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 lose energy. This energy is used to pump
protons from the matrix into the space between the inner
and outer mitochondrial membranes.
• The resulting high concentration of protons creates a
concentration gradient of protons and a charge gradient
across the inner membrane.
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Chapter 7
• As protons move through ATP synthase and down their
concentration and electrical gradients, ATP is produced.
Oxygen combines with the electrons and protons to form
water.
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Chapter 7
• The Importance of Oxygen
– ATP can be synthesized by chemiosmosis only if
electrons continue to move along the electron transport
chain.
– By accepting electrons from the last molecule in 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
Efficiency of Cellular Respiration
• Cellular respiration can produce up to 38 ATP
molecules from the oxidation of a single molecule of
glucose. Most eukaryotic cells produce about 36 ATP
molecules per molecule of glucose.
• Thus, cellular respiration is nearly 20 times more
efficient than glycolysis alone.
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Chapter 7
A Summary of Cellular Respiration
• Another Role of Cellular Respiration
– Providingn cells with ATP is not the only important
function of cellular respiration.
– Molecules formed at different steps in glycolysis
and the Krebs cycle are often used by cells to
make compounds that are missing in food.
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Chapter 7
Summary of Cellular Respiration
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Chapter 7
Multiple Choice
1. Which of the following must pyruvic acid be
converted into before the Krebs cycle can proceed?
A. NADH
B. glucose
C. citric acid
D. acetyl CoA
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Chapter 7
Multiple Choice, continued
1. Which of the following must pyruvic acid be
converted into before the Krebs cycle can proceed?
A. NADH
B. glucose
C. citric acid
D. acetyl CoA
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Chapter 7
2. Which of the following occurs in lactic acid
fermentation?
F. Oxygen is consumed.
G. Lactic acid is converted into pyruvic acid.
H. NAD+ is regenerated for use in glycolysis.
J. Electrons pass through the electron transport chain.
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Chapter 7
2. Which of the following occurs in lactic acid
fermentation?
F. Oxygen is consumed.
G. Lactic acid is converted into pyruvic acid.
H. NAD+ is regenerated for use in glycolysis.
J. Electrons pass through the electron transport chain.
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Chapter 7
3. Which of the following is not a product of the Krebs
cycle?
A. CO2
B. ATP
C. FADH2
D. ethyl alcohol
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Chapter 7
3. Which of the following is not a product of the Krebs
cycle?
A. CO2
B. ATP
C. FADH2
D. ethyl alcohol
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Chapter 7
4. In which way is cellular respiration similar to
photosynthesis?
F. They both make G3P.
G. They both involve ATP.
H. They both involve chemiosmosis.
J. all of the above
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Chapter 7
4. In which way is cellular respiration similar to
photosynthesis?
F. They both make G3P.
G. They both involve ATP.
H. They both involve chemiosmosis.
J. all of the above
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Chapter 7
5. ATP is synthesized in chemiosmosis when which of
the following moves across the inner mitochondrial
membrane?
A. NADH
B. oxygen
C. protons
D. citric acid
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Chapter 7
5. ATP is synthesized in chemiosmosis when which of
the following moves across the inner mitochondrial
membrane?
A. NADH
B. oxygen
C. protons
D. citric acid
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Chapter 7
The illustration shows
6. This reaction occurs during
part of a biochemical pathway.
which of the following
Use the illustration to
processes?
answer the question that follows.
F. Krebs cycle
G. acetyl CoA formation
H. alcoholic fermentation
J. lactic acid fermentation
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Chapter 7
The illustration shows
6. This reaction occurs during
part of a biochemical pathway.
which of the following
Use the illustration to
processes?
answer the question that follows.
F. Krebs cycle
G. acetyl CoA formation
H. alcoholic fermentation
J. lactic acid fermentation
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Chapter 7
7. glycolysis : pyruvic acid :: Krebs cycle :
A. O2
B. ATP
C. lactic acid
D. acetyl CoA
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Chapter 7
7. glycolysis : pyruvic acid :: Krebs cycle :
A. O2
B. ATP
C. lactic acid
D. acetyl CoA
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Chapter 7
The illustration below
8. At which of the points is
shows some stages and reactants
ATP, the main energy
of cellular respiration. Use the
currency of the cell,
illustration to answer the
produced?
question that follows.
F. 1 only
G. 2 only
H. 1 and 3
J. 1, 2, and 3
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Chapter 7
The illustration below
8. At which of the points is
shows some stages and reactants
ATP, the main energy
of cellular respiration. Use the
currency of the cell,
illustration to answer the
produced?
question that follows.
F. 1 only
G. 2 only
H. 1 and 3
J. 1, 2, and 3
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Chapter 7
Short Response
The inner membrane of a mitochondrion is folded;
these folds are called cristae.
How might cellular respiration be different if the inner
mitochondrial membrane were not folded??
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Chapter 7
Short Response, continued
The inner membrane of a mitochondrion is folded;
these folds are called cristae.
How might cellular respiration be different if the inner
mitochondrial membrane were not folded?
Answer:
The cristae increase the surface area of the inner
wall of the mitochondria, which allows more electron
transport chain pathways and ATP synthase. Thus,
the rate of cellular respiration is increased.
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Chapter 7
Extended Response
Oxygen is produced during the reactions of
photosynthesis, and it is used in the reactions of
cellular respiration.
Part A How does oxygen get into or out of
chloroplasts and mitochondria?
Part B What are the roles of oxygen in the processes
of photosynthesis and cellular respiration, and
how are the roles similar?
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Chapter 7
Extended Response, continued
Answer:
Part A Oxygen builds up inside chloroplasts as they produce
oxygen, forming a concentration gradient—high oxygen
concentration inside and low concentration outside. This causes
O2 to diffuse out of the chloroplast. In mitochondria, as O2 is
used up, a favorable gradient for the inward diffusion of oxygen
occurs.
Part B In photosynthesis, oxygen is formed when water is split
during the light reactions. This byproduct of photosynthesis is
released by cells and becomes available for aerobic respiration.
In aerobic respiration, oxygen is the final electron acceptor at
the end of electron transport. When oxygen accepts these
electrons (and protons), water is formed. Hence, water supplies
oxygen for photosynthesis, and oxygen is used to form water in
aerobic respiration.
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Chapter 7
Electron Transport Chain and Chemiosmosis
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