Transcript Chapter 9 Notes

Chapter 9
Cellular Respiration:
Harvesting Chemical Energy
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
AP Biology Curriculum Standards
Big Idea #2
Growth, reproduction and maintenance of the organization of living systems require free
energy and matter.
Essential Understanding 2A:
Growth, reproduction and maintenance of the organization of living systems require free
energy and matter.
Essential Knowledge 2.A.1
All living systems require constant input of free energy.
1. Order is maintained by constant free energy input into the system.
2. Loss of order or free energy flow results in death.
3. Increased disorder and entropy are offset by biological processes that maintain or
increase order.
Essential Knowledge 2.A.2
Organisms capture and store free energy for use in biological processes.
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Energy Flow in Ecosystems
– Flows into an ecosystem as sunlight and
leaves as heat
Light energy
ECOSYSTEM
Photosynthesis
in chloroplasts
Organic
CO2 + H2O
+ O2
Cellular
molecules
respiration
in mitochondria
ATP
powers most cellular work
Figure 9.2
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Heat
energy
Section 9.1
Catabolic Pathways and Production of ATP
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Catabolic Pathways
• To keep working
– Cells must regenerate ATP
• Catabolic pathways yield energy by oxidizing
organic fuels
• The breakdown of organic molecules is
exergonic
• One catabolic process, fermentation
– Is a partial degradation of sugars that occurs
without oxygen
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Cellular Respiration
• Is the most prevalent and efficient catabolic
pathway
• Consumes oxygen and organic molecules such as
glucose
• Yields ATP
• Catabolic pathways yield energy
– Due to the transfer of electrons
– Is controlled by allosteric enzymes at key
points in glycolysis and the citric acid cycle
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Oxidation-Reduction Reactions (Redox)
• Redox reactions
– Transfer electrons from one reactant to
another by oxidation and reduction
– Coupling of oxidation – reduction reactions
• In oxidation
– A substance loses electrons, or is oxidized
• In reduction
– A substance gains electrons, or is reduced
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Sample Redox Reaction
• Examples of redox reactions
becomes oxidized
(loses electron)
Na
+
Cl
Na+
+
becomes reduced
(gains electron)
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Cl–
Redox with electron sharing
• Some redox reactions
– Do not completely exchange electrons
– Change the degree of electron sharing in
covalent bonds
Products
Reactants
becomes oxidized
+
CH4
CO
2O2
+
Energy
2 H2O
becomes reduced
O
O
C
O
H
O
O
H
H
H
C
+
2
H
H
Methane
(reducing
agent)
Oxygen
(oxidizing
agent)
Figure 9.3
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Carbon dioxide
Water
Oxidation of Organic Fuel Molecules
During Cellular Respiration
• During cellular respiration
– Glucose is oxidized and oxygen is reduced
becomes oxidized
C6H12O6 + 6O2
6CO2 + 6H2O + Energy
becomes reduced
• Stepwise energy harvest via NAD+ and the
Electron Transport Chain
- Oxidizes glucose in a series of steps
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Catabolism of Various Food Molecules
• The catabolism of various molecules from food
Proteins
Carbohydrates
Amino
acids
Sugars
Fats
Glycerol
Glycolysis
Glucose
Glyceraldehyde-3- P
NH3
Pyruvate
Acetyl CoA
Citric
acid
cycle
Figure 9.19
Oxidative
phosphorylation
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Fatty
acids
Electron Carriers
• Electrons from organic compounds
– Are usually first transferred to NAD+, a
coenzyme
2 e– + 2 H+
NAD+
Dehydrogenase
O
NH2
H
C
CH2
O
O–
O
O P
O
H
–
O P O HO
O
N+ Nicotinamide
(oxidized form)
H
OH
HO
CH2
NH2
N
N
H
O
H
HO
N
H
OH
N
2 e– + H+
H
Reduction of NAD+
+ 2[H]
(from food) Oxidation of NADH
NADH
H O
C
H
N
NH2
+
Nicotinamide
(reduced form)
NADH, the reduced form of
NAD+ passes the electrons to
the electron transport chain
Figure 9.4
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Why the Gradual Release of Energy?
• If electron transfer is not stepwise
– A large release of energy occurs
– As in the reaction of hydrogen and oxygen to
form water
Thermite REDOX Rxn
Figure 9.5 A
Free energy, G
H2 + 1/2 O2
Explosive
release of
heat and light
energy
H2O
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(a) Uncontrolled reaction
Role of the Electron Transport Chain
• The electron transport chain
– Passes electrons in a series of steps instead of
in one explosive reaction
– Uses the energy from the electron transfer to
2H
+
/ O
form ATP
1
2
2
1/
O2
(from food via NADH)
ETP & ATP Synthesis
Free energy, G
2 H+ + 2 e–
Controlled
release of
energy for
synthesis of
ATP
ATP
ATP
ATP
2 e–
2 H+
H2O
Figure 9.5 B
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(b) Cellular respiration
2
The Stages of Cellular Respiration
• Respiration is a cumulative function of three
metabolic stages
– Glycolysis
– The citric acid cycle (or Krebs Cycle)
– Oxidative phosphorylation
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Overview of Stages of Aerobic Cellular Respiration
• Glycolysis
– Breaks down glucose into two molecules of
pyruvate
• The citric acid cycle
– Completes the breakdown of glucose
• Oxidative phosphorylation
– Is driven by the electron transport chain
– Generates ATP
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An overview of cellular respiration
Electrons carried
via NADH and
FADH2
Electrons
carried
via NADH
Citric
acid
cycle
Glycolsis
Pyruvate
Glucose
Cytosol
Mitochondrion
ATP
Figure 9.6
Oxidative
phosphorylation:
electron
transport and
chemiosmosis
Substrate-level
phosphorylation
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ATP
Substrate-level
phosphorylation
ATP
Oxidative
phosphorylation
Substrate-Level Phosphorylation
• Both glycolysis and the citric acid cycle
– Can generate ATP by substrate-level
phosphorylation
Enzyme
Enzyme
ADP
P
Substrate
+
Figure 9.7
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Product
ATP
Concept 9.2: Glycolysis
• Glycolysis harvests energy by oxidizing
glucose to pyruvate
• Glycolysis
– Means “splitting of sugar”
– Breaks down glucose into pyruvate
– Occurs in the cytoplasm of the cell
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Phases of Glycolysis
• Glycolysis consists of two major phases
– Energy investment phase
– Energy payoff phase
Citric
acid
cycle
Glycolysis
Oxidative
phosphorylation
ATP
ATP
ATP
Energy investment phase
Glucose
2 ATP + 2 P
2 ATP
used
Energy payoff phase
4 ADP + 4 P
2 NAD+ + 4 e- + 4 H
+
4 ATP formed
2 NADH + 2 H+
2 Pyruvate + 2 H2O
Glucose
4 ATP formed – 2 ATP used
Figure 9.8
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2 NAD+ + 4 e– + 4 H
+
2 Pyruvate + 2 H2O
2 ATP + 2 H+
2 NADH
A Closer Look at the Phases
6
Triose phosphate
dehydrogenase
2 NAD+
CH2OH
HH
H
HO H
HO
OH
H OH
Glycolysis
Citric
Oxidative
acid
cyclephosphorylation
2 Pi
2 NADH
+ 2 H+
2
Glucose
P
O C O
CHOH
ATP
1
CH2 O P
1, 3-Bisphosphoglycerate
2 ADP
7
Phosphoglycerokinase
Hexokinase
ADP
CH2OH P
HH OH
OHH
HO
H OH
2 ATP
O–
2
C
CHOH
Glucose-6-phosphate
2
CH2 O P
3-Phosphoglycerate
8
Phosphoglyceromutase
Phosphoglucoisomerase
CH2O P
O CH2OH
H HO
HO
H
HO H
2
C
Fructose-6-phosphate
ATP
O–
O
H C O
3
Phosphofructokinase
ADP
2
2
P O CH2O CH2 O P
HO
H
OH
HO H
Fructose1, 6-bisphosphate
O–
C O
C O
4
Pyruvate kinase
2 ATP
5
H
P O CH2 Isomerase
C O
C O
CHOH
CH2OH
CH2 O P
Figure 9.9 A
Glyceraldehyde3-phosphate
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P
CH2
Phosphoenolpyruvate
2 ADP
10
Aldolase
Dihydroxyacetone
phosphate
P
CH2OH
2-Phosphoglycerate
9
Enolase
2H O
2
O–
C O
C O
Figure 9.8 B
CH3
Pyruvate
Overview of Glycolysis
http://www.uic.edu/classes/bios/bios100/lectures/respiration.htm
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Overview of the Link Reaction
http://www.uic.edu/classes/bios/bios100/lectures/respiration.htm
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Glycolysis IPOD
Input:
Processes:
Output:
Details/Description
1. Location:
2. Electron Carrier (s):
3. Purpose:
4. Next step:
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Concept 9.3: The Citric Acid Cycle
• The citric acid cycle completes the energyyielding oxidation of organic molecules
• The citric acid (or Krebs) cycle
– Takes place in the matrix of the mitochondrion
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The Link Reaction
• Before the citric acid cycle can begin
– Pyruvate must first be converted to acetyl CoA,
which links the cycle to glycolysis
CYTOSOL
MITOCHONDRION
NAD+
NADH
+ H+
O–
S
CoA
C
O
2
C
C
O
O
1
3
CH3
Pyruvate
Transport protein
Figure 9.10
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CH3
Acetyle CoA
CO2
Coenzyme A
TCA Overview
• An overview of the citric acid cycle
Pyruvate
(from glycolysis,
2 molecules per glucose)
Glycolysis
Citric
acid
cycle
ATP
ATP
Oxidative
phosphorylatio
n
ATP
CO2
CoA
NADH
+ 3 H+ Acetyle CoA
CoA
CoA
Citric
acid
cycle
2 CO2
3 NAD+
FADH2
FAD
3 NADH
+ 3 H+
ADP + P i
ATP
Figure 9.11
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A closer look at the citric acid cycle
Glycolysis
Citric
Oxidative
acid phosphorylation
cycle
S
CoA
C
O
CH3
Acetyl CoA
CoA SH
O
NADH
+ H+
C COO–
COO–
1
CH2
COO–
NAD+
CH2
HO C COO–
8 Oxaloacetate
CH2
COO–
HO CH
H2O
COO–
CH2
2
HC COO–
COO–
Malate
HO
Citrate
CH2
COO–
Isocitrate
COO–
H2O
CH
7
COO–
CH
CO2
Citric
acid
cycle
3
NAD+
COO–
Fumarate
HC
CH2
CoA SH
6
CoA SH
COO–
FAD
CH2
CH2
COO–
C O
Succinate
Pi
S
CoA
GTP GDP Succinyl
CoA
ADP
ATP
Figure 9.12
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4
C O
COO–
CH2
5
CH2
FADH2
COO–
NAD+
NADH
+ H+
+ H+
a-Ketoglutarate
CH2
COO–
NADH
CO2
Overview of Citric Acid (Krebs) Cycle
http://www.uic.edu/classes/bios/bios100/lectures/09_15_citric_acid_cycle-L.jpg
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Change in Free Energy During Glucose Breakdown
http://www.uic.edu/classes/bios/bios100/lectures/respiration.htm
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Citric Acid Cycle IPOD
Input:
Processes:
Output:
Details/Description
1. Location:
2. Electron Carrier (s):
3. Purpose:
4. Next step:
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Concept 9.4: Oxidative Phosphorylation
• During oxidative phosphorylation,
chemiosmosis couples electron transport to
ATP synthesis
• NADH and FADH2
– Donate electrons to the electron transport
chain, which powers ATP synthesis via
oxidative phosphorylation
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The Pathway of Electron Transport
•
In the electron transport chain
–
•
Electrons from NADH and FADH2 lose energy in several steps
At the end of the chain
–
Electrons are passed to oxygen, forming water
Free energy (G) relative to O2 (kcl/mol)
50
NADH
FADH2
40
FMN
I
Fe•S
FAD
Fe•S II
O
30
20
Multiprotein
complexes
III
Cyt b
Fe•S
Cyt c1
IV
Cyt c
Cyt a
Cyt a3
10
0
Figure 9.13
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2 H + + 12 O2
H2 O
Chemiosmosis: The Energy-Coupling Mechanism
• ATP synthase
– Is the enzyme that actually makes ATP
INTERMEMBRANE SPACE
H+
H+
H+
H+
H+
H+
H+
A rotor within the
membrane spins
clockwise when
H+ flows past
it down the H+
gradient.
A stator anchored
in the membrane
holds the knob
stationary.
H+
ADP
+
Pi
Figure 9.14
MITOCHONDRIAL MATRIX
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ATP
A rod (for “stalk”)
extending into
the knob also
spins, activating
catalytic sites in
the knob.
Three catalytic
sites in the
stationary knob
join inorganic
Phosphate to ADP
to make ATP.
The Electron Transport Chain
• At certain steps along the electron transport
chain
– Electron transfer causes protein complexes to
pump H+ from the mitochondrial matrix to the
intermembrane space
• The resulting H+ gradient
– Stores energy
– Drives chemiosmosis in ATP synthase
– Is referred to as a proton-motive force
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Chemiosmosis
• Chemiosmosis
– Is an energy-coupling mechanism that uses
energy in the form of a H+ gradient across a
membrane to drive cellular work
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Chemiosmosis and the electron transport chain
Oxidative
phosphorylation.
electron transport
and chemiosmosis
Glycolysis
ATP
Inner
Mitochondrial
membrane
ATP
ATP
H+
H+
H+
Intermembrane
space
Protein complex
of electron
carners
Q
I
Inner
mitochondrial
membrane
H+
Cyt c
IV
III
FADH2
FAD+
NADH+
NAD+
2 H+ + 1/2 O2
H2O
ADP +
(Carrying electrons
from, food)
Mitochondrial
matrix
ATP
synthase
II
ATP
Pi
H+
Chemiosmosis
Electron transport chain
Electron transport and pumping of protons (H+), ATP synthesis powered by the flow
which create an H+ gradient across the membrane Of H+ back across the membrane
Figure 9.15
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Oxidative phosphorylation
An Accounting of ATP Production
by Cellular Respiration
• During respiration, most energy flows in this
sequence
– Glucose to NADH to electron transport chain to
proton-motive force to ATP
• About 40% of the energy in a glucose molecule
– Is transferred to ATP during cellular
respiration, making approximately 38 ATP
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Summary of ATP Production from Glucose
Electron shuttles
span membrane
CYTOSOL
MITOCHONDRION
2 NADH
or
2 FADH2
2 NADH
2 NADH
Glycolysis
Glucose
2
Pyruvate
6 NADH
Citric
acid
cycle
2
Acetyl
CoA
+ 2 ATP
by substrate-level
phosphorylation
Maximum per glucose:
+ 2 ATP
by substrate-level
phosphorylation
2 FADH2
Oxidative
phosphorylation:
electron transport
and
chemiosmosis
+ about 32 or 34 ATP
by oxidative phosphorylation, depending
on which shuttle transports electrons
from NADH in cytosol
About
36 or 38 ATP
Figure 9.16
• There are three main processes in this
metabolic enterprise
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Overview of the ETC
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Oxidative Phosphorylation IPOD
Input:
Processes:
REDOX (Oxygen)
Output:
Details/Description
1. Location:
2. Electron Carrier (s):
3. Purpose:
4. Next step:
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Overview of Cellular Respiration
http://www.uic.edu/classes/bios/bios100/lectures/respiration.htm
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Concept 9.5: Anaerobic Cellular Respiration
• Fermentation enables some cells to produce
ATP without the use of oxygen
• Cellular respiration
– Relies on oxygen to produce ATP
• In the absence of oxygen
– Cells can still produce ATP through
fermentation
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Aerobic or Anaerobic Respiration?
http://www.uic.edu/classes/bios/bios100/lectures/09_24_energy_production-L.jpg
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Glycolysis
• Glycolysis
– Can produce ATP with or without oxygen, in
aerobic or anaerobic conditions
– Couples with fermentation to produce ATP
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Types of Fermentation
• Fermentation consists of
– Glycolysis plus reactions that regenerate
NAD+, which can be reused by glycolysis
• In alcohol fermentation
– Pyruvate is converted to ethanol in two steps,
one of which releases CO2
• During lactic acid fermentation
– Pyruvate is reduced directly to NADH to form
lactate as a waste product
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Types of Fermentation
2 ADP + 2
P1
2 ATP
O–
C O
Glucose
Glycolysis
C O
CH3
2 Pyruvate
2 NADH
2 NAD+
H
2 CO2
H
H C OH
C O
CH3
CH3
2 Ethanol
2 Acetaldehyde
(a) Alcohol fermentation
2 ADP + 2
Glucose
P1
2 ATP
Glycolysis
O–
C O
C O
O
2 NAD+
2 NADH
CH3
C O
H
C OH
CH3
2 Lactate
Figure 9.17
(b) Lactic acid fermentation
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Fermentation and Cellular Respiration Compared
• Both fermentation and cellular respiration
– Use glycolysis to oxidize glucose and other
organic fuels to pyruvate
• Fermentation and cellular respiration
– Differ in their final electron acceptor
• Cellular respiration
– Produces more ATP
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Fermentation IPOD
Input:
Processes:
Output:
Details/Description
1. Location:
2. Electron Carrier (s):
3. Purpose:
4. Next step:
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