Chapter 9 Cellular Respiration
Copyright Pearson Prentice Hall
9-1 Chemical Pathways
Both plant and animal cells carry out the final
stages of cellular respiration in the mitochondria.
Animal Cells
Animal
Mitochondrion
Plant
Plant Cells
Chemical Energy and Food
One gram of glucose (C6H12O6), when burned in
the presence of oxygen, releases 3811 calories of
heat energy.
A calorie is the amount of energy needed to raise
the temperature of 1 gram of water 1 degree
Celsius.
Overview of Cellular Respiration
Cellular respiration is the process that releases
energy by breaking down glucose and other food
molecules in the presence of oxygen.
Matrix
Intermembrane Space
Overview of Cellular Respiration*
The equation for cellular respiration is:
6O2 + C6H12O6 → 6CO2 + 6H2O + Energy
oxygen + glucose → carbon dioxide + water + Energy
Overview of Cellular Respiration*
Glycolysis takes place in the cytoplasm. The
Krebs cycle and electron transport take place in
the mitochondria.
Glycolysis
Cytoplasm
Mitochondrion
Glycolysis*
ATP Production
At the beginning of glycolysis, the cell uses up
2 molecules of ATP to start the reaction.
2 ATP
2 ADP
4 ADP
4 ATP
Glucose
2 Pyruvic
acid
Glycolysis*
When glycolysis is complete, 4 ATP molecules
have been produced.
This gives the cell a net gain of 2 ATP molecules.
2 ATP
2 ADP
4 ADP
4 ATP
Glucose
2 Pyruvic
acid
Glycolysis
Remember from Photosynthesis?
High energy electron carrier NADP+
Cellular respiration uses different carriers to transport
high energy electrons. NAD+ FAD
Glycolysis
NADH Production
One molecule of glucose (6 carbons) is split into two
molecules of pyruvic acid (3 carbons).
Requires energy in the form of ATP.
Yields 2 ATP
Yields 2 NADH
2 ATP
2 ADP
4 ADP
4 ATP
Glucose
2NAD+
2
Glycolysis*
The Advantages of Glycolysis
The process of glycolysis is so fast that cells can
produce thousands of ATP molecules in a few
milliseconds.
Glycolysis does not require oxygen.
Fermentation*
When oxygen is not present, glycolysis
follows a different pathway, called
fermentation. producing ATP in the absence
of oxygen.
Fermentation
Fermentation does not require oxygen—it is an
anaerobic process.
Two main types of fermentation.
Fermentation*
Alcoholic Fermentation
Yeasts and a few other microorganisms use
alcoholic fermentation, forming ethyl alcohol
and carbon dioxide as wastes.
pyruvic acid + NADH → alcohol + CO2 + NAD+
Fermentation*
Lactic Acid Fermentation
Pyruvic acid that accumulates as a result of
glycolysis can be converted to lactic acid.
pyruvic acid + NADH → lactic acid + NAD+
9.1 Concept Assessment
1. Describe the process of cellular respiration.
2. Key Concept What are the products of glycolysis?
3. Key Concept Name the two main types of fermentation.
4. What is a calorie? A Calorie?
5. How is the function of NAD + similar to that of NADP +?
6. Critical Thinking Comparing and Contrasting How are
lactic acid fermentation and alcoholic fermentation
similar? How are they different?
9.1 QUIZ
9.1 Vocab
calorie
glycolysis
cellular respiration
NAD+ (nicotinamide adenine dinucleotide)
fermentation
anaerobic
Quiz 9.1
1- The raw materials required for cellular
respiration are
A. carbon dioxide and oxygen.
B. glucose and water.
C. glucose and oxygen.
D. carbon dioxide and water.
Quiz 9.1
2- Glycolysis occurs in the
A. mitochondria.
B. cytoplasm.
C. nucleus.
D. chloroplasts
Quiz 9.1
3- The net gain of ATP molecules after
glycolysis is
A. 3 ATP molecules.
B. 2 ATP molecules.
C. 3 pyruvic acid molecules.
D. 4 pyruvic acid molecules
Quiz 9.1
4- Fermentation releases energy from food
molecules in the absence of
A. oxygen.
B. glucose.
C. NADH.
D. alcohol.
Quiz 9.1
5- The two main types of fermentation are
called
A. alcoholic and lactic acid.
B. lactic acid and anaerobic.
C. aerobic and anaerobic.
D. alcoholic and aerobic.
Quiz 9.1
6- Which of the following acts as an
electron carrier in cellular respiration?
A. NAD+
B. pyruvic acid
C. ATP
D. ADP
Quiz 9.1
7- Which of the following is NOT a product
of glycolysis?
A. NADH
B. pyruvic acid
C. ATP
D. glucose
Quiz 9.1
8- One cause of muscle soreness is
A. alcoholic fermentation.
B. the Krebs cycle.
C. glycolysis
D. lactic acid fermentation
Quiz 9.1
9- The starting molecule for glycolysis is
A. pyruvic acid.
B. glucose.
C. ADP
D. citric acid
Quiz 9.1
10- Which of these is a product of cellular
respiration?
A. glucose.
B. oxygen.
C. water
D. all of the above
9-2 The Krebs Cycle
In the presence of oxygen, Krebs cycle begins
when pyruvic acid produced by glycolysis
enters the mitochondrion.
The Krebs Cycle
The Krebs Cycle
Pyruvic acid from glycolysis is converted into a
usable form, Acetyl CoA.
The Krebs Cycle
One carbon molecule is removed, forming CO2,
and electrons are removed, changing NAD+ to
NADH.
The Krebs Cycle
Acetyl-CoA then adds the 2-carbon acetyl group
to a 4-carbon compound, forming citric acid.
The Krebs Cycle
Citric acid is broken down into a 5-carbon
compound, then into a 4-carbon compound.
The Krebs Cycle
Two more molecules of CO2 are released and
electrons join NAD+ and FAD, forming NADH
and FADH2
The Krebs Cycle
In addition, one molecule of ATP is generated.
The Krebs Cycle
The Krebs Cycle
The energy tally from 1 molecule of pyruvic acid
is
4 NADH
1 FADH2
1 ATP
3 CO2
The Krebs Cycle
Happens if oxygen is present.
Pyruvates break down further so that the carbon
and oxygen atoms end up in CO2.
The Krebs Cycle
Hydrogens and electrons are stripped and
loaded onto NAD+ and FAD to produce NADH
and FADH2
2 more ATP produced, but loads several
electron carriers that will be used in the 3rd
stage.
Electron Transport
The electron transport chain uses the highenergy electrons from the Krebs cycle to
convert ADP into ATP.
Electron Transport
High-energy electrons from NADH and FADH2
are passed along the electron transport chain
from one carrier protein to the next.
Electron Transport
At the end of the chain, an enzyme combines
these electrons with hydrogen ions and
oxygen to form water.
Electron Transport
As the final electron acceptor of the electron
transport chain, oxygen gets rid of the lowenergy electrons and hydrogen ions.
Electron Transport
When 2 high-energy electrons move down
the electron transport chain, their energy is
used to move hydrogen ions (H+) across
the membrane.
Electron Transport
During electron transport, H+ ions build up
in the intermembrane space, so it is
positively charged.
Electron Transport
The other side of the membrane, from which
those H+ ions are taken, is now negatively
charged.
Electron Transport
Electron Transport
As H+ ions escape through channels, the
ATP synthase spins.
Channel
ATP
synthase
Electron Transport
As it rotates, the enzyme grabs a lowenergy ADP, attaching a phosphate, forming
high-energy ATP.
Channel
ATP
synthase
ATP
The Totals
The breakdown of glucose through cellular
respiration, including glycolysis, results in
the production of 36 molecules of ATP.
The Totals
The Totals
Cells contain small No of ATP produced during glycolysis and
cellular respiration. In a quick exercise muscles contain only
enough of this ATP for a few seconds. That store of ATP is
quickly gone. At this point, muscle cells are producing most of
their ATP by lactic acid fermentation. That will last about 90
seconds.
The only way to get rid of lactic acid is in a chemical pathway
that requires extra oxygen. To repay, you have to do plenty of
heavy breathing to get the O2.
For anything longer cellular respiration is the only way to
generate a continuing supply of ATP. Cellular respiration
releases energy slower than fermentation, which is why even
well-conditioned athletes have to pace themselves during a
9.2 Concept Assessment
1. What happens to pyruvic acid during the Krebs cycle?
2. How does the electron transport chain use the high-energy
electrons from the Krebs cycle?
3. Why is cellular respiration considered to be much more efficient
than glycolysis alone?
4. How many molecules of ATP are produced in the entire
breakdown of glucose?
5. Compare the energy flow in photosynthesis to the energy flow
in cellular respiration.
6. How is the chemical energy in glucose similar to money in a
savings account?
9.2 Quiz
9.2 Quiz
1. The Krebs cycle breaks pyruvic acid
down into
A. oxygen.
B. NADH.
C. carbon dioxide.
D. alcohol.
9.2 Quiz
2. What role does the Krebs cycle play in the
cell?
A. It breaks down glucose and releases its stored
energy.
B. It releases energy from molecules formed during
glycolysis.
C. It combines carbon dioxide and water into highenergy molecules.
D. It breaks down ATP and NADH, releasing stored
energy.
9.2 Quiz
3. In eukaryotes, the electron transport
chain is located in the
A. cell membrane.
B. inner mitochondrial membrane.
C. cytoplasm.
D. outer mitochondrial membrane.
9.2 Quiz
4. To generate energy over long periods,
the body must use
A. stored ATP.
B. lactic acid fermentation.
C. cellular respiration.
D.glycolysis
9.2 Quiz
5. Which statement correctly describes
photosynthesis and cellular respiration?
A. Photosynthesis releases energy, while cellular
respiration stores energy.
B. Photosynthesis and cellular respiration use the
same raw materials.
C. Cellular respiration releases energy, while
photosynthesis stores energy.
D. Cellular respiration and photosynthesis produce
the same products.
9.2 Quiz
6. The Krebs cycle starts with
A. glucose and yields 32 ATPs.
B. pyruvic acid and yields carbon dioxide.
C. pyruvic acid and yields lactic acid or
alcohol.
D. lactic acid and yields carbon dioxide.
9.2 Quiz
7. The starting molecule for the Krebs
cycle is
A. NADH
B. coenzyme
C. pyruvic acid.
D. glucose.
9.2 Quiz
8. The Krebs cycle produces
A. glucose
B. lactic acid
C. electron carriers
D. oxygen
9.2 Quiz
9. Photosynthesis is to chloroplasts as
cellular respiration is to
A. chloroplasts
B. nuclei
C. bytoplasm
D. mitochondria
9.2 Quiz
10. The Krebs cycle does not occur if
A. glycolysis occurs
B. carbon dioxide is present
C. oxygen is present
D. fermentation occurs
9.2 Quiz
11. Which of the following is the correct sequence
of events in cellular respiration?
A.
B.
C.
D.
Krebs cycle —- glycolysis —- electron transport
glycolysis —- fermentation —- Krebs cycle
Krebs cycle —- electron transport —- glycolysis
glycolysis —- Krebs cycle —- electron transport
9.2 Quiz
12. Cellular respiration is called an
aerobic process because it requires
A. exercise
B. light
C. glucose
D. oxygen
Chapter 9 Test