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PLANT SCIENCE 184
Cellular Respiration:
Harvesting Chemical Energy
PowerPoint® Lecture Slides for
Essential Biology, Second Edition & Essential Biology with Physiology
Neil Campbell, Jane Reece, and Eric Simon
Presentation prepared by Chris C. Romero
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
• Bacteria are used to
produce yogurt, sour
cream, pepperoni, and
cheese
• Both carbon monoxide
and cyanide kill by
disrupting cellular
respiration
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• All the energy in all the food you
eat can be traced back to sunlight
• If you exercise too hard, your
muscles shut down from a
lack of oxygen
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BIOLOGY AND SOCIETY:
FEELING THE “BURN”
• When you exercise
– Muscles need energy in order to perform work
– Your cells use oxygen to release energy from the
sugar glucose
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• Aerobic metabolism
– When enough oxygen reaches cells to support energy
needs
• Anaerobic metabolism
– When the demand for oxygen outstrips the body’s
ability to deliver it
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• Anaerobic metabolism
– Without enough oxygen, muscle cells break down
glucose to produce lactic acid
– Lactic acid is associated with the “burn” associated
with heavy exercise
– If too much lactic acid builds up, your muscles give
out
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• Physical conditioning
allows your body to adapt
to increased activity
– The body can increase its
ability to deliver oxygen
to muscles
• Long-distance runners
wait until the final sprint
to exceed their aerobic
capacity
Figure 6.1
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ENERGY FLOW AND CHEMICAL CYCLING
IN THE BIOSPHERE
• Fuel molecules in food represent solar energy
– Energy stored in food can be traced back to the sun
• Animals depend on plants to convert solar energy to
chemical energy
– This chemical energy is in the form of sugars and
other organic molecules
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Producers and Consumers
• Photosynthesis
– Light energy from the sun powers a chemical process
that makes organic molecules
– This process occurs in the leaves of terrestrial plants
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• Autotrophs
– “Self-feeders”
– Plants and other organisms that make all their own
organic matter from inorganic nutrients
• Heterotrophs
– “Other-feeders”
– Humans and other animals that cannot make organic
molecules from inorganic ones
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• Producers
– Biologists refer to plants
and other autotrophs as
the producers in an
ecosystem
• Consumers
– Heterotrophs are
consumers, because they
eat plants or other
animals
Figure 6.2
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Chemical Cycling Between Photosynthesis and
Cellular Respiration
• The ingredients for photosynthesis are carbon
dioxide and water
– CO2 is obtained from the air by a plant’s leaves
– H2O is obtained from the damp soil by a plant’s roots
• Chloroplasts rearrange the atoms of these
ingredients to produce sugars (glucose) and other
organic molecules
– Oxygen gas is a by-product of photosynthesis
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• Both plants and animals perform cellular respiration
– Cellular respiration is a chemical process that
harvests energy from organic molecules
– Cellular respiration occurs in mitochondria
• The waste products of cellular respiration, CO2 and
H2O, are used in photosynthesis
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Sunlight
energy
Ecosystem
Photosynthesis
(in chloroplasts)
Carbon dioxide
Glucose
Oxygen
Water
Cellular respiration
(in mitochondria)
for cellular work
Heat energy
Figure 6.3
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CELLULAR RESPIRATION: AEROBIC
HARVEST OF FOOD ENERGY
• Cellular respiration
– The main way that chemical energy is harvested from
food and converted to ATP
– This is an aerobic process—it requires oxygen
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The Relationship Between Cellular Respiration
and Breathing
• Cellular respiration and breathing are closely related
– Cellular respiration requires a cell to exchange gases
with its surroundings
– Breathing exchanges these gases between the blood
and outside air
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Breathing
Lungs
Muscle
cells
Cellular
respiration
Figure 6.4
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The Overall Equation for Cellular Respiration
• A common fuel molecule for cellular respiration is
glucose
– This is the overall equation for what happens to
glucose during cellular respiration
Glucose
Oxygen
Carbon
dioxide
Water
Energy
Unnumbered Figure 6.1
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The Role of Oxygen in Cellular Respiration
• During cellular respiration, hydrogen and its
bonding electrons change partners
– Hydrogen and its electrons go from sugar to oxygen,
forming water
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Redox Reactions
• Chemical reactions that transfer electrons from one
substance to another are called oxidation-reduction
reactions
– Redox reactions for short
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• The loss of electrons during a redox reaction is
called oxidation
• The acceptance of electrons during a redox reaction
is called reduction
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Oxidation
[Glucose loses electrons (and hydrogens)]
Glucose
Oxygen
Carbon
dioxide
Water
Reduction
[Oxygen gains electrons (and hydrogens)]
Unnumbered Figure 6.2
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•RS IS NECESSARY IN ALL LIVING CELLS.
•PLANTS ARE WELL KNOWN FOR PS, BUT THEY
MUST ALSO REPIRE IN ORDER TO
SURVIVE.
• PS - OCCURS ONLY IN PLANT CELLS
CONTAINING CHLOROPHYLL DURING THE
DAYLIGHT HOURS.
•RS - OCCURS IN ALL OF A PLANT’S LIVING
CELLS 24 -7.
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WHY IS RS NECESSARY?
PLANTS NEED ENERGY TO PERFORM MANY
ESSENTIAL FUNCTIONS OF LIFE:
GROWTH,
REPAIR,
NUTRIENT MOVEMENT,
REPRODUCTION, &
NUTRIENT TRANSPORT.
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The *Metabolic Pathway of Cellular Respiration
• Cellular respiration is an example of a metabolic
pathway
– A series of chemical reactions in cells –building or
degradation process
• All of the reactions involved in cellular respiration can be
grouped into three main stages
– Glycolysis
– The Krebs cycle
– Electron transport
– * WHAT IS METABOLISM?
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A Road Map for Cellular Respiration
Cytosol
Mitochondrion
High-energy
electrons
carried
mainly by
NADH
High-energy
electrons
carried
by NADH
Glycolysis
Glucose
2
Pyruvic
acid
Krebs
Cycle
Electron
Transport
Figure 6.7
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Glycolysis
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Stage 1: Glycolysis
• Glycolysis breaks a six-carbon glucose into two
three-carbon molecules
– These molecules then donate high energy electrons to
NAD+, forming NADH
• A molecule of glucose is split into two molecules of
pyruvic acid
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2 Pyruvic acid
Glucose
Figure 6.8
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Krebs Cycle
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Stage 2: The Krebs Cycle
• The Krebs cycle completes the breakdown of sugar
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• In the Krebs cycle, pyruvic acid from glycolysis is
first “prepped” into a usable form, Acetyl-CoA
CoA
2
Acetic
acid
1
Pyruvic
acid
CO2
3
Acetyl-CoA
(acetyl-coenzyme A)
Coenzyme A
Figure 6.10
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• The Krebs cycle extracts the energy of sugar by
breaking the acetic acid molecules all the way down
to CO2
– The cycle uses some of this energy to make ATP
– The cycle also forms NADH and FADH2
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Input
Output
2
1 Acetic acid
2 CO2
ADP
3
Krebs
Cycle
3 NAD
4
FAD
5
6
Figure 6.11
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Electron Transport
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Stage 3: Electron Transport
• Electron transport releases the energy your cells
need to make the most of their ATP
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• The molecules of electron transport chains are built
into the inner membranes of mitochondria
– The chain functions as a chemical machine that uses
energy released by the “fall” of electrons to pump
hydrogen ions across the inner mitochondrial
membrane
– These ions store potential energy
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Protein
complex
Electron
carrier
Inner
mitochondrial
membrane
Electron
flow
Electron transport chain
ATP synthase
Figure 6.12
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The Versatility of Cellular Respiration
• Cellular respiration can “burn” other kinds of
molecules besides glucose
– Diverse types of carbohydrates
– Fats
– Proteins
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Food
Polysaccharides
Sugars
Glycerol
Fats
Fatty acids
Proteins
Amino acids
Amino groups
Glycolysis
AcetylCoA
Krebs
Cycle
Electron
Transport
Figure 6.13
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Adding Up the ATP from Cellular Respiration
Cytosol
Mitochondrion
Glycolysis
Glucose
2
Pyruvic
acid
2
AcetylCoA
Krebs
Cycle
Electron
Transport
Maximum
per
glucose:
by direct
synthesis
by
direct
synthesis
by
ATP
synthase
Figure 6.14
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
FERMENTATION: ANAEROBIC HARVEST OF
FOOD ENERGY
• Some of your cells can actually work for short
periods without oxygen
– For example, muscle cells can produce ATP under
anaerobic conditions
• Fermentation
– The anaerobic harvest of food energy
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Fermentation in Human Muscle Cells
• Human muscle cells can make ATP with and without
oxygen
– They have enough ATP to support activities such as
quick sprinting for about 5 seconds
– A secondary supply of energy (creatine phosphate)
can keep muscle cells going for another 10 seconds
– To keep running, your muscles must generate ATP by
the anaerobic process of fermentation
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• Glycolysis is the metabolic pathway that provides
ATP during fermentation
– Pyruvic acid is reduced by NADH, producing
NAD+, which keeps glycolysis going
– In human muscle cells, lactic acid is a by-product
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
2 ADP+ 2
Glycolysis
2 NAD
2 NAD
Glucose
2 Pyruvic
acid
+ 2 H
2 Lactic
acid
(a) Lactic acid fermentation
Figure 6.15a
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Fermentation in Microorganisms
• Various types of microorganisms perform
fermentation
– Yeast cells carry out a slightly different type of
fermentation pathway
– This pathway produces CO2 and ethyl alcohol
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
2 ADP+ 2
2 CO2 released
2 ATP
Glycolysis
2 NAD
2 NAD
Glucose
2 Pyruvic
acid
+ 2 H
2 Ethyl
alcohol
(b) Alcoholic fermentation
Figure 6.15b
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• The food industry uses yeast to produce various
food products
Figure 6.16
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EVOLUTION CONNECTION:
LIFE ON AN ANAEROBIC EARTH
• Ancient bacteria probably used glycolysis to make
ATP long before oxygen was present in Earth’s
atmosphere
– Glycolysis is a metabolic heirloom from the earliest
cells that continues to function today in the harvest
of food energy
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SUMMARY OF KEY CONCEPTS
• Chemical Cycling Between Photosynthesis and
Cellular Respiration
Heat
Sunlight
Photosynthesis
Cellular
respiration
Visual Summary 6.1
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
• The Overall Equation for Cellular Respiration
Oxidation:
Glucose loses electrons
(and hydrogens)
Glucose
Carbon dioxide
Electrons
(and hydrogens)
Oxygen
Energy
Reduction:
Oxygen gains
electrons (and
hydrogens)
Visual Summary 6.2
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
• The Metabolic Pathway of Cellular Respiration
Glucose
Oxygen
Water
Energy
Visual Summary 6.3
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings