Transcript cellular respiration

Chapter 6
Cellular Respiration: Obtaining
Energy from Food
PowerPoint® Lectures for
Campbell Essential Biology, Fourth Edition
– Eric Simon, Jane Reece, and Jean Dickey
Campbell Essential Biology with Physiology, Third Edition
– Eric Simon, Jane Reece, and Jean Dickey
Lectures by Chris C. Romero, updated by Edward J. Zalisko
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• Plant and animal cells perform cellular respiration, a chemical
process that:
– Primarily occurs in mitochondria
– Harvests energy stored in organic molecules
– Uses oxygen
– Generates ATP
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• The waste products of cellular respiration are:
– CO2 and H2O
– Used in photosynthesis
• Animals perform only cellular respiration.
• Plants perform:
– Photosynthesis and
– Cellular respiration
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Study the
relationship of
photosynthesis &
cell respiration
C6H12O6
Sunlight energy
enters ecosystem
Photosynthesis
CO2
Glucose
Carbon dioxide
O2
Oxygen
H2O
Water
Cellular respiration
ATP drives cellular work
Heat energy exits ecosystem
Figure 6.2
CELLULAR RESPIRATION:
AEROBIC HARVEST OF FOOD ENERGY
• Cellular respiration is:
– The main way that chemical energy is harvested from food and converted
to ATP
– An aerobic process—it requires oxygen
• Cellular respiration and breathing are closely related.
– Cellular respiration requires a cell to exchange gases with its
surroundings.
–
Cells take in oxygen gas.
–
Cells release waste carbon dioxide gas.
– Breathing exchanges these same gases between the blood and outside air.
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O2
CO2
Breathing
Lungs
CO2
O2
Cellular
respiration
Muscle
cells
Figure 6.3a
The overall equation for what happens to
glucose during cellular respiration:
Oxidation
Glucose loses electrons
(and hydrogens)
C6H12O6
Glucose
 6
O2
Oxygen
6
CO2
Carbon
dioxide
 6
H 2O
Water
Reduction
Oxygen gains electrons (and hydrogens)
Figure 6.UN02
The Role of Oxygen in Cellular Respiration
• Cellular respiration can produce up to 38 ATP molecules for each
glucose molecule consumed.
• During cellular respiration, hydrogen and its bonding electrons
change partners.
– Hydrogen and its electrons go from sugar to oxygen, forming water.
– This hydrogen transfer is why oxygen is so vital to cellular respiration.
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An Overview of Cellular Respiration
• Cellular respiration:
– Is an example of a metabolic pathway, which is a series of chemical
reactions in cells
• All of the reactions involved in cellular respiration can be
grouped into three main stages:
– Glycolysis
– The citric acid cycle
– Electron transport
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Cytoplasm
Mitochondrion
High-energy
electrons
carried
by NADH
Glycolysis
Glucose
2
Pyruvic
acid
ATP
High-energy
electrons carried
mainly by
NADH
Citric
Acid
Cycle
Electron
Transport
ATP
ATP
Figure 6.6a
Stage 1: Glycolysis
• A six-carbon glucose molecule is split in half to form two
molecules of pyruvic acid.
• These two molecules then donate high energy electrons to NAD+,
forming NADH.
– Uses two ATP molecules per glucose to split the six-carbon glucose
– Makes four additional ATP directly when enzymes transfer phosphate
groups from fuel molecules to ADP
• Thus, glycolysis produces a net of two molecules of ATP per
glucose molecule.
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Stage 2: The Citric Acid Cycle
• The citric acid cycle completes the breakdown of sugar.
• The citric acid cycle:
– Extracts the energy of sugar by breaking the acetic acid molecules all the
way down to CO2
– Uses some of this energy to make ATP
– Forms NADH and FADH2
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INPUT
OUTPUT
Citric
acid
Acetic
acid
2 CO2
ADP  P
ATP
Citric
Acid
Cycle
3
NAD
3
FAD
NADH
FADH2
Acceptor
molecule
Figure 6.10
INPUT
OUTPUT
Oxidation of the fuel
generates NADH
(from glycolysis)
NAD
(to citric acid cycle)
NADH
CoA
Pyruvic acid
Pyruvic acid
loses a carbon
as CO2
Acetic acid
CO2
Coenzyme A
Acetic acid
attaches to
coenzyme A
Acetyl CoA
Figure 6.9
Stage 3: Electron Transport
• The molecules of the electron transport chain 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.
• When the hydrogen ions flow back through the membrane, they
release energy.
– The hydrogen ions flow through ATP synthase.
– ATP synthase:
–
Takes the energy from this flow
–
Synthesizes ATP
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Space
between
H
membranes
Electron
carrier
Protein
complex
H
H
H
H
H
FADH2
FAD
H
H
H
H
H
H
H
Inner
mitochondrial
membrane
Electron
flow
1
2
NADH
H
Matrix
H
NAD
H
O2  2 H
H2O
ADP  P
H
Electron transport chain
H
ATP
H
ATP synthase
Figure 6.11a
Cytoplasm
Mitochondrion
2
NADH
Glycolysis
Glucose
2
Pyruvic
acid
2
NADH
2
Acetyl
CoA
6
NADH
2
FADH2
Citric
Acid
Cycle
2
ATP
2
ATP
by direct
synthesis
by direct
synthesis
Electron
Transport
Maximum
per
glucose:
About
34 ATP
About
38 ATP
by ATP
synthase
Figure 6.13
• Cyanide is a deadly poison that:
– Binds to one of the protein complexes in the electron transport chain
– Prevents the passage of electrons to oxygen
– Stops the production of ATP
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The Versatility of Cellular Respiration
• In addition to glucose, cellular respiration can “burn”:
– Diverse types of carbohydrates
– Fats
– Proteins
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FERMENTATION: ANAEROBIC HARVEST
OF FOOD ENERGY
• Some of your cells can actually work for short periods without
oxygen.
• Fermentation is the anaerobic (without oxygen) harvest of food
energy.
• After functioning anaerobically for about 15 seconds:
– Muscle cells will begin to generate ATP by the process of fermentation
• Fermentation relies on glycolysis to produce ATP.
• In human muscle cells, lactic acid is a by-product.
© 2010 Pearson Education, Inc.
INPUT
2 ADP
2 P
OUTPUT
2 ATP
Glycolysis
2 NAD 2 NADH
Glucose
2 NADH 2 NAD
2 Pyruvic
 2 H
acid
2 Lactic acid
Figure 6.14
• Yeast are a type of microscopic fungus that:
– Use a different type of fermentation
– Produce CO2 and ethyl alcohol instead of lactic acid
• This type of fermentation, called alcoholic fermentation, is used
to produce:
– Beer
– Wine
– Breads
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INPUT
2 ADP
2 P
OUTPUT
2 ATP
2 CO2 released
Glycolysis
2 NAD 2 NADH
Glucose
2 NADH 2 NAD
2 Pyruvic
 2 H
acid
2 Ethyl alcohol
Bread with air
bubbles produced
by fermenting yeast
Beer
fermentation
Figure 6.16