Cellular Respiration

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Chapter 6
Cellular Respiration: Obtaining
Energy from Food
PowerPoint® Lectures for
Campbell Essential Biology, Fifth Edition, and
Campbell Essential Biology with Physiology,
Fourth Edition
– Eric J. Simon, Jean L. Dickey, and Jane B. Reece
Lectures by Edward J. Zalisko
© 2013 Pearson Education, Inc.
Biology and Society:
Marathoners versus Sprinters
• Slow-twitch fibers
– last longer,
– do not generate a lot of quick power, and
– generate ATP using oxygen (aerobically).
© 2013 Pearson Education, Inc.
Biology and Society:
Marathoners versus Sprinters
• Fast-twitch fibers
– contract more quickly and powerfully,
– fatigue more quickly, and
– can generate ATP without using oxygen
(anaerobically).
• All human muscles contain both types of fibers but
in different ratios.
© 2013 Pearson Education, Inc.
ENERGY FLOW AND CHEMICAL CYCLING
IN THE BIOSPHERE
• Animals depend on plants to convert the energy of
sunlight to
– chemical energy of sugars and
– other organic molecules we consume as food.
• Photosynthesis uses light energy from the sun to
– power a chemical process and
– make organic molecules.
© 2013 Pearson Education, Inc.
Producers and Consumers
• Plants and other autotrophs (self-feeders)
– make their own organic matter from inorganic
nutrients.
• Heterotrophs (other-feeders)
– include humans and other animals that cannot
make organic molecules from inorganic ones.
• Autotrophs are producers because ecosystems
depend upon them for food.
• Heterotrophs are consumers because they eat
plants or other animals.
© 2013 Pearson Education, Inc.
Chemical Cycling between Photosynthesis and
Cellular Respiration
• The ingredients for photosynthesis are carbon
dioxide (CO2) and water (H2O).
– CO2 is obtained from the air by a plant’s leaves.
– H2O is obtained from the damp soil by a plant’s
roots.
© 2013 Pearson Education, Inc.
Chemical Cycling between Photosynthesis and
Cellular Respiration
• Chloroplasts in the cells of leaves use light energy
to rearrange the atoms of CO2 and H2O, which
produces
– sugars (such as glucose),
– other organic molecules, and
– oxygen gas.
© 2013 Pearson Education, Inc.
Chemical Cycling between Photosynthesis and
Cellular Respiration
• Plant and animal cells perform cellular
respiration, a chemical process that
– primarily occurs in mitochondria,
– harvests energy stored in organic molecules,
– uses oxygen, and
– generates ATP.
• The waste products of cellular respiration are
– CO2 and H2O,
– used in photosynthesis.
© 2013 Pearson Education, Inc.
Chemical Cycling between Photosynthesis and
Cellular Respiration
• Animals perform only cellular respiration.
• Plants perform
– photosynthesis and
– cellular respiration.
• Plants usually make more organic molecules than
they need for fuel. This surplus provides material
that can be
– used for the plant to grow or
– stored as starch in potatoes.
© 2013 Pearson Education, Inc.
Figure 6.2
Sunlight energy
enters ecosystem
Photosynthesis
C6H12O6
CO2
O2
H2O
Cellular respiration
ATP
drives cellular work
Heat energy exits
ecosystem
CELLULAR RESPIRATION:
AEROBIC HARVEST OF FOOD ENERGY
• Cellular respiration is
– the main way that chemical energy is harvested
from food and converted to ATP and
– an aerobic process—it requires oxygen.
© 2013 Pearson Education, Inc.
CELLULAR RESPIRATION:
AEROBIC HARVEST OF FOOD ENERGY
• 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.
© 2013 Pearson Education, Inc.
Figure 6.3
O2
CO2
Breathing
Lungs
O2
CO2
Cellular
respiration
Muscle
cells
The Simplified Equation for Cellular Respiration
• A common fuel molecule for cellular respiration is
glucose.
• Cellular respiration can produce up to 32 ATP
molecules for each glucose molecule consumed.
• The overall equation for what happens to glucose
during cellular respiration is
– glucose & oxygen  CO2, H2O, & a release of
energy.
© 2013 Pearson Education, Inc.
Figure 6.UN01
• During cellular respiration, hydrogen and its
bonding electrons change partners from sugar
to oxygen, forming water as a product.
C6H12O6
Glucose
6
O2
Oxygen
6
CO2
Carbon
dioxide
6
H2O
ATP
Water
Energy
Chemical reactions that transfer electrons from one
substance to another are called
oxidation-reduction reactions or
redox reactions for short.
Redox Reactions
• The loss of electrons during a redox reaction is
oxidation.
• The acceptance of electrons during a redox
reaction is reduction.
• During cellular respiration
– glucose is oxidized and
– oxygen is reduced.
© 2013 Pearson Education, Inc.
Figure 6.UN02
Oxidation
Glucose loses electrons
(and hydrogens)
C6H12O6
Glucose
6
O2
Oxygen
6
CO2
Carbon
dioxide
6 H2O
Water
Reduction
Oxygen gains electrons (and hydrogens)
Redox Reactions
• Why does electron transfer to oxygen release
energy?
– When electrons move from glucose to oxygen, it is
as though the electrons were falling.
– This “fall” of electrons releases energy during
cellular respiration.
• Cellular respiration is
– a controlled fall of electrons and
– a stepwise cascade much like going down a
staircase.
© 2013 Pearson Education, Inc.
Figure 6.4
1
2
H2
Release
of heat
energy
H2O
O2
NADH and Electron Transport Chains
• The path that electrons take on their way down
from glucose to oxygen involves many steps.
• The first step is an electron acceptor called NAD+.
– NAD is made by cells from niacin, a B vitamin.
– The transfer of electrons from organic fuel to
NAD+ reduces it to NADH.
• The rest of the path consists of an electron
transport chain, which
– involves a series of redox reactions and
– ultimately leads to the production of large
amounts of ATP.
© 2013 Pearson Education, Inc.
Figure 6.5
e e
Electrons from food
e e
NADH
NAD
2 H
Stepwise release
of energy used
to make
ATP
2 e
2 e
2 H
Hydrogen, electrons,
and oxygen combine
to produce water
1
2
H2O
O2
Figure 6.5a
2 H
ATP
2 e
Stepwise release
of energy used
to make ATP
Electron
transport chain
2 e
2 H
Hydrogen, electrons, and oxygen
combine to produce water
1
2
H2O
O2
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:
1. glycolysis,
2. the citric acid cycle, and
3. electron transport.
BioFlix Animation: Cellular Respiration
© 2013 Pearson Education, Inc.
Figure 6.6
Mitochondrion
Cytoplasm
Cytoplasm
Animal cell
Plant cell
Cytoplasm
Mitochondrion
High-energy
electrons
via carrier
molecules
Glycolysis
2
Pyruvic
acid
Glucose
ATP
Citric
Acid
Cycle
ATP
Electron
Transport
ATP
Figure 6.6a
Cytoplasm
Mitochondrion
High-energy
electrons
via carrier
molecules
Glycolysis
Glucose
ATP
2
Pyruvic
acid
Citric
Acid
Cycle
ATP
Electron
Transport
ATP
Stage 1: Glycolysis
1. A six-carbon glucose molecule is split in half to
form two molecules of pyruvic acid.
2. These two molecules then donate high energy
electrons to NAD+, forming NADH.
© 2013 Pearson Education, Inc.
Figure 6.7
OUTPUT
INPUT
– –
NADH
P
2 ATP
P
NAD
P
2 ATP
2 ADP
2
3
2 ADP
P
2 Pyruvic acid
1
P
P
P
2
3
Glucose
NAD
Energy investment phase
Key
Carbon atom
P Phosphate group
– High-energy electron
2 ADP
– –
NADH
P
2 ATP
Energy harvest phase
Figure 6.7a
INPUT
OUTPUT
2 Pyruvic acid
Glucose
Figure 6.7b-1
P
2 ATP
2 ADP
1
Energy investment phase
P
Figure 6.7b-2
– –
NADH
P
2 ATP
P
2 ADP
1
2
P
P
P
P
NAD
Energy investment phase
P
NAD
2
– –
NADH
P
Energy harvest phase
Figure 6.7b-3
– –
NADH
P
2 ATP
1
3
P
P
P
P
2
3
2 ADP

NAD
Energy investment phase
2 ATP
2 ADP
2
P
2 ADP
P
NAD
– –
NADH
P
2 ATP
Energy harvest phase
Stage 1: Glycolysis
3. Glycolysis
– uses two ATP molecules per glucose to split the
six-carbon glucose and
– 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.
© 2013 Pearson Education, Inc.
Figure 6.8
Enzyme
P
P
ADP
ATP
P
Stage 2: The Citric Acid Cycle
• In the citric acid cycle, pyruvic acid from glycolysis
is first “groomed.”
– Each pyruvic acid loses a carbon as CO2.
– The remaining fuel molecule, with only two carbons
left, is acetic acid.
• Oxidation of the fuel generates NADH.
© 2013 Pearson Education, Inc.
Stage 2: The Citric Acid Cycle
• Finally, each acetic acid is attached to a molecule
called coenzyme A to form acetyl CoA.
• The CoA escorts the acetic acid into the first
reaction of the citric acid cycle.
• The CoA is then stripped and recycled.
© 2013 Pearson Education, Inc.
Figure 6.9
INPUT
OUTPUT
2 Oxidation of the fuel
generates NADH
– –
NADH
NAD
(from
glycolysis)
(to citric
acid cycle)
CoA
Pyruvic acid
1 Pyruvic acid
loses a carbon
as CO2
Acetic
acid
CO2
Coenzyme A
3 Acetic acid
attaches to
coenzyme A
Acetyl CoA
Figure 6.9a
INPUT
OUTPUT
(from
glycolysis)
(to citric
acid cycle)
CoA
Pyruvic acid
Acetyl CoA
Figure 6.9b
2 Oxidation of the fuel
generates NADH
– –
NADH
NAD
1 Pyruvic acid
loses a carbon
as CO2
Acetic
acid
CO2
Coenzyme A
OUTPUT
3 Acetic acid
attaches to
coenzyme A
Stage 2: The Citric Acid Cycle
• 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, and
– forms NADH and FADH2.
Blast Animation: Harvesting Energy: Krebs Cycle
© 2013 Pearson Education, Inc.
Figure 6.10
INPUT
OUTPUT
Citric
acid
1 Acetic
acid
2 CO2
ADP  P
ATP
Citric
Acid
Cycle
3
2
3
NAD
– –
3 NADH
4
FAD
– –
FADH2
5

6
Acceptor
molecule
Figure 6.10a
INPUT
1 Acetic
acid
ADP  P
OUTPUT
2 CO2
ATP
2
3
3 NAD
– –
3 NADH
4
FAD
– –
FADH2
5
Figure 6.10b
INPUT
Citric
acid
OUTPUT
Citric
Acid
Cycle
Acceptor
molecule
Stage 3: Electron Transport
• Electron transport releases the energy your cells
need to make the most of their ATP.
• The molecules of the electron transport chain
are built into the inner membranes of mitochondria.
• The chain
– functions as a chemical machine, which
– uses energy released by the “fall” of electrons to
pump hydrogen ions across the inner mitochondrial
membrane, and
– uses these ions to store potential energy.
© 2013 Pearson Education, Inc.
Stage 3: Electron Transport
• 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 and
– synthesizes ATP.
© 2013 Pearson Education, Inc.
Figure 6.11
H
Space
between
membranes
H
H
H
H
H

H
Electron
carrier
H
H
H

H
H
3
5
H
Protein
complex
Inner
mitochondrial
membrane
–
–
FADH2
Electron
flow
FAD
H
2
–
1
2
–
1
H
2
H
H2O
6
4
NAD
NADH
O2
ADP
H
H
ATP
P
H
H
Matrix
Electron transport chain
ATP synthase
Figure 6.11a
Space
between
membranes
H
H
H
H
H
Electron
carrier
H

H
H
H
H
H
3
H
5
H
Protein
complex
Inner
mitochondrial
membrane
–
–
FADH2
Electron
flow
FAD
H
2
–
1
2
–
1
H

2 H
H2O
6
4
NAD
NADH
O2
ADP
H
H
ATP
P
H
H
Matrix
Electron transport chain
ATP synthase
Figure 6.11b
Space
between
membranes
H
H
Electron
carrier
H
H
H
H
H
H
H
H
H
3
Protein
complex
Inner
mitochondrial
membrane
–
–
FADH2
Electron
flow
FAD
H
2
–
1
2
–
1
4

NADH
NAD
H
H
H
Matrix
O2
Electron transport chain
H
2 H
Figure 6.11c
H
H

H
H
H
5
1
2
O2
2 H
H
6
H2O
4
ADP
H
ATP
P
H
ATP synthase
Stage 3: Electron Transport
• 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, and
– stops the production of ATP.
© 2013 Pearson Education, Inc.
Figure 6.12
Cytoplasm
Mitochondrion
–
2
–
–
NADH
2
–
NADH
6
–
2
Glycolysis
Glucose
2
Pyruvic
acid
2
ATP
by direct
synthesis
2
Acetyl
CoA
– –
NADH
–
FADH2
Citric
Acid
Cycle
Electron
Transport
2
ATP
About
28 ATP
by direct
synthesis
Maximum
per
glucose:
by ATP
synthase
About
32 ATP
Figure 6.12a
Glycolysis
2
Pyruvic
acid
2
Acetyl
CoA
Citric
Acid
Cycle
Electron
Transport
2
ATP
2
ATP
About
28 ATP
by direct
synthesis
by direct
synthesis
Glucose
by ATP
synthase
The Results of Cellular Respiration
• In addition to glucose, cellular respiration can
“burn”
– diverse types of carbohydrates,
– fats, and
– proteins.
© 2013 Pearson Education, Inc.
Figure 6.13
Food
Polysaccharides
Fats
Proteins
Sugars
Fatty acids
Amino acids
Glycerol
Glycolysis
Acetyl
CoA
Citric
Acid
Cycle
Electron
Transport
ATP
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.
© 2013 Pearson Education, Inc.
Fermentation in Human Muscle Cells
• After functioning anaerobically for about 15
seconds, muscle cells begin to generate ATP by
the process of fermentation.
• Fermentation relies on glycolysis to produce ATP.
• Glycolysis
– does not require oxygen and
– produces two ATP molecules for each glucose
broken down to pyruvic acid.
© 2013 Pearson Education, Inc.
Fermentation in Human Muscle Cells
• Pyruvic acid, produced by glycolysis,
– is reduced by NADH,
– producing NAD+, which
– keeps glycolysis going.
• In human muscle cells, lactic acid is a by-product.
Animation: Fermentation Overview
© 2013 Pearson Education, Inc.
Figure 6.14
INPUT
OUTPUT
2 ADP
2 P
2 ATP
Glycolysis
2 NAD
– –
2 NADH
– –
2 NADH
2 Pyruvic acid
Glucose
2 H
2 NAD
2 Lactic acid
Figure 6.14a
OUTPUT
INPUT
2 ADP
2 P
2 ATP
Glycolysis
2 NAD
– –
2 NADH
– –
2 NADH
2 Pyruvic acid
Glucose

2 H
2 NAD
2 Lactic acid
Figure 6.15
Battery
Battery

–

Force
measured
–
Force
measured
Frog
muscle
stimulated
by electric
current
Solution prevents
diffusion of lactic acid
Solution allows
diffusion of lactic acid;
muscle can work for
twice as long
The Process of Science:
What Causes Muscle Burn?
• Results: When lactic acid could diffuse away,
performance improved greatly.
• Conclusion: Lactic acid accumulation is the
primary cause of failure in muscle tissue.
• However, recent evidence suggests that the role of
lactic acid in muscle function remains unclear.
© 2013 Pearson Education, Inc.
Fermentation in Microorganisms
• Fermentation alone is able to sustain many types
of microorganisms.
• The lactic acid produced by microbes using
fermentation is used to produce
– cheese, sour cream, and yogurt,
– soy sauce, pickles, and olives, and
– sausage meat products.
© 2013 Pearson Education, Inc.
Fermentation in Microorganisms
• Yeast is a microscopic fungus that
– uses a different type of fermentation and
– produces CO2 and ethyl alcohol instead of lactic
acid.
• This type of fermentation, called alcoholic
fermentation, is used to produce
– beer,
– wine, and
– breads.
© 2013 Pearson Education, Inc.
Figure 6.16
INPUT
OUTPUT
2 ADP
2 P
2 ATP
2 CO2 released
Glycolysis
2 NAD
Glucose
–
–
–
2 NADH
–
2 NADH
2 Pyruvic
acid
 2 H
2 NAD
2 Ethyl alcohol
Figure 6.16a
INPUT
OUTPUT
2 ADP
2 P
2 ATP
2 CO2 released
Glycolysis
2 NAD
Glucose

–
–
–
–
2 NADH 2 NAD
2 NADH
2 Pyruvic
acid
2 H
2 Ethyl alcohol
Evolution Connection:
Life before and after Oxygen
• Glycolysis could be used by ancient bacteria to
make ATP
– when little oxygen was available, and
– before organelles evolved.
• Today, glycolysis
– occurs in almost all organisms and
– is a metabolic heirloom of the first stage in the
breakdown of organic molecules.
© 2013 Pearson Education, Inc.
Figure 6.17
2.1
2.2
2.7
O2 present in
Earth’s atmosphere
Billions of years ago
0
First eukaryotic organisms
Atmospheric oxygen reaches 10% of modern levels
Atmospheric oxygen
first appears
3.5
Oldest prokaryotic
fossils
4.5
Origin of Earth
0
2.1
2.2
2.7
O2 present in
Earth’s atmosphere
Billions of years ago
Figure 6.17a
First eukaryotic organisms
Atmospheric oxygen reaches 10% of modern levels
Atmospheric oxygen
first appears
3.5
Oldest prokaryotic
fossils
4.5
Origin of Earth
Figure 6.UN03
Glycolysis
Citric
Acid
Cycle
Electron
Transport
ATP
ATP
ATP
Figure 6.UN04
Glycolysis
Citric
Acid
Cycle
Electron
Transport
ATP
ATP
ATP
Figure 6.UN05
Glycolysis
Citric
Acid
Cycle
Electron
Transport
ATP
ATP
ATP
Figure 6.UN06
Heat
C6H12O6
Sunlight
O2
ATP
Cellular
respiration
Photosynthesis
CO2
H2O
Figure 6.UN08
Oxidation
Glucose loses electrons
(and hydrogens)
CO2
C6H12O6
ATP
Electrons
(and hydrogens)
O2
H 2O
Reduction
Oxygen gains
electrons (and
hydrogens)
Figure 6.UN09
Mitochondrion
O2
–
2
–
–
NADH
2
–
6
NADH
2
Glycolysis
Glucose
2
Acetyl
CoA
2
Pyruvic
acid
– –
NADH
– –
FADH2
Citric
Acid
Cycle
2 CO2
2
ATP
by direct
synthesis
Electron
Transport
4 CO2
by direct
synthesis
2
ATP
About
32 ATP
H2O
About
28 ATP
by ATP
synthase
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