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Respiration
How Cells Harvest Chemical
Energy
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
INTRODUCTION TO CELLULAR RESPIRATION
6.1 Photosynthesis and cellular respiration
provide energy for life
• Cellular respiration makes ATP and consumes O2
– During the oxidation of glucose to CO2 and
H2O
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• Photosynthesis uses solar energy
Sunlight energy
To produce glucose and
O2 from CO2 and H2O
ECOSYSTEM
Photosynthesis in
chloroplasts
CO2
Glucose
+
+
H2O
O2
Cellular respiration in
mitochondria
ATP
(for cellular work)
Heat energy
Figure 6.1
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
6.2 Breathing supplies oxygen to our cells and
removes carbon dioxide
• Breathing provides for the exchange of O2 and CO2
between an organism and its environment
O2
Breathing
CO2
Lungs
CO2
Bloodstream
O2
Muscle cells carrying out
Cellular Respiration
Glucose + O2
Figure 6.2
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
CO2 + H2O + ATP
6.3 Cellular respiration stores energy in ATP
molecules
• Cellular respiration breaks down glucose
molecules
– And stores their energy in ATP
C6H12O6
Glucose
+
6
O2
Oxygen gas
Figure 6.3
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
6
CO2
Carbon
dioxide
+
6
H2O
Water
+
ATPs
Energy
6.4 The human body uses energy from ATP for
all its activities
ATP powers almost all
cellular and body
activities
Table 6.4
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
6.5 Cells tap energy from electrons “falling”
from organic fuels to oxygen
• Electrons lose potential energy
– During their transfer from organic
compounds to oxygen
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• When glucose is converted to carbon dioxide
– It loses hydrogen atoms, which are
added to oxygen, producing water
Loss of hydrogen atoms
(oxidation)
C6H12O6 + 6 O2
6 CO2
+
Glucose
6 H2O + Energy
(ATP)
Gain of hydrogen atoms
(reduction)
Figure 6.5A
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• Dehydrogenase removes electrons (in
hydrogen atoms) from fuel molecules (oxidation)
– And transfers them to NAD+ (reduction)
Oxidation
H
NAD+
O + 2H
H
O
Dehydrogenase
Reduction
NADH
2H
+
+
2H
+
2e

Figure 6.5B
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
(carries
2 electrons)
+
H+
• NADH passes electrons to an electron transport chain
• As electrons “fall” from carrier to carrier and finally to O2
–
Energy is released in small quantities
NADH
NAD
+
H
+
ATP

2e
+
Controlled
release of
energy for
synthesis of
ATP

2e
2
H
+
1
2
H2O
Figure 6.5C
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O2
STAGES OF CELLULAR RESPIRATION AND
FERMENTATION
• 6.6 Overview: Cellular respiration occurs in
three main stages
• Cellular respiration
– Occurs in three main stages
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• Stage 1: Glycolysis
– Occurs in the cytoplasm
– Breaks down glucose into pyruvate,
producing a small amount of ATP
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• Stage 2: The citric acid cycle
– Takes place in the mitochondria
– Completes the breakdown of glucose,
producing a small amount of ATP
– Supplies the third stage of cellular
respiration with electrons
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• Stage 3: Oxidative phosphorylation
– Occurs in the mitochondria
– Uses the energy released by “falling”
electrons to pump H+ across a
membrane
– Harnesses the energy of the H+ gradient
through chemiosmosis, producing ATP
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• An overview of cellular respiration
NADH
High-energy
electrons
carried by NADH
NADH
FADH2
and
GLYCOLYSIS
Glucose
Pyruvate
CITRIC ACID
CYCLE
OXIDATIVE
PHOSPHORYLATION
(Electron Transport
and Chemiosmosis)
Mitochondrion
Cytoplasm
ATP
Substrate-level
phosphorylation
CO2
ATP
CO2
Substrate-level
phosphorylation
Figure 6.6
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
ATP
Oxidative
phosphorylation
6.7 Glycolysis harvests chemical energy by oxidizing
glucose to pyruvate
• In glycolysis, ATP is used to energize a glucose
molecule
–
Which is split into two molecules of pyruvate
NAD+
2
2
NADH
+ 2
H+
Glucose
2 Pyruvate
2 ADP
Figure 6.7A
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
+2
P
2
ATP
• Glycolysis produces ATP by substrate-level
phosphorylation
In which a
phosphate group
is transferred from
an organic
molecule to ADP
Figure 6.7B
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
The conversion of phosphoenolpyruvate to pyruvate is
another example of substrate level phosphorylation.
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• In the first phase of glycolysis
– ATP is used to energize a glucose
molecule, which is then split in two
Steps 1 – 3 A fuel molecule is energized,
using ATP.
Glucose
ATP
PREPARATORY PHASE
(energy investment)
Step
1
ADP
P
Glucose-6-phosphate
P
Fructose-6-phosphate
P
Fructose-1,6-diphosphate
2
ATP
3
ADP
P
Step 4 A six-carbon intermediate splits
into two three-carbon intermediates.
Figure 6.7C
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4
• In the second phase of glycolysis
– ATP, NADH, and pyruvate are formed
P
Step 5 A redox reaction generates
6
9
NADH.
NAD
P
+
5
+
5
P 6 NADH
+H+
P
P
NADH
+H+
P
Steps 6 – 9 ATP and pyruvate
are produced.
NAD
Glyceraldehyde-3-phosphate
(G3P)
ADP
P
6
P 1,3-Diphosphoglycerate
ADP
6
ATP
7
6
ATP
P
P
7
P
8
8
H2O
7
P 3-Phosphoglycerate
7
8
2-Phosphoglycerate
8
H2O
P
P
9
ADP
Phosphoenolpyruvate
(PEP) 9
ADP
9
ATP
ENERGY PAYOFF PHASE
9
ATP
Pyruvate
Figure 6.7C
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
6.8 The Link reaction (between glycolysis and Citric acid cycle)
• Prior to the citric acid cycle
–
Enzymes process pyruvate, releasing CO2
and producing NADH and acetyl CoA
NAD+
NADH
+ H+
2
CoA
Pyruvate
1
3
CO2
Figure 6.8
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Coenzyme A
Acetyl CoA
(acetyl coenzyme A)
When pyruvate enters the matrix of mitochondria it is
converted to acetylCoA. Coenzyme A (CoA) is a large
molecule (and a vitamin) that acts as a coenzyme.
The conversion of pyruvate to acetylCoA is an coupled
oxidation-reduction reaction in which high energy electrons
are removed from pyruvate and end up in NADH. The three
carbon pyruvate is split into CO2 and the two carbon acetate.
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
6.9 The citric acid cycle completes the oxidation of organic
fuel, generating many NADH and FADH2 molecules
Acetyl CoA
• In the citric acid cycle
CoA
CoA
The two-carbon acetyl
part of acetyl CoA is
oxidized
2 CO2
CITRIC ACID CYCLE
3
FADH2
3
FAD
NAD+
NADH
+
3 H+
ATP
Figure 6.9A
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ADP
+
P
• The two carbons are added to a four-carbon
compound, forming citrate
– Which is then degraded back to the
starting compound
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• For each turn of the cycle
CoA
Acetyl CoA
CoA
Two CO2
molecules are
released
The energy
yield is
one ATP,
three NADH,
and one FADH2
2 carbons enter cycle
Oxaloacetate
Citrate
NADH
+ H+
CO2
NAD+
CITRIC ACID CYCLE
leaves cycle
NAD+
1
Malate
NADH
ADP
5
FADH2
+
+ H+
P
ATP
2
Alpha-ketoglutarate
FAD
CO2
4
3
NADH
Step
Acetyl CoA stokes the furnace.
1
Figure 6.9B
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
leaves cycle
Succinate
Steps
2
and
+ H+
NAD+
Steps
and
NADH, ATP, and CO2 are generated during Redox reactions generate FADH and
2
4
3
5
redox
reactions.
NADH.
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
6.10 Most ATP production occurs by oxidative
phosphorylation
• Electrons from NADH and FADH2
– Travel down the electron transport chain
to oxygen, which picks up H+ to form
water
• Energy released by the redox reactions
– Is used to pump H+ into the space
between the mitochondrial membranes
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• In chemiosmosis, the H+ diffuses back through the
inner membrane through ATP synthase
complexes --Driving the synthesis of ATP
H+
H+
H+
H+
+
.
H
H+
Protein
complex
H+
Electron
carrier
Intermembrane
space
H+
H+
ATP
synthase
Inner
mitochondrial
membrane
FADH2
Electron
flow
FAD
NAD+
NADH
H+
Mitochondrial
matrix
1
O + 2 H+
2 2
H+
H+
Electron Transport Chain
OXIDATIVE PHOSPHORYLATION
Figure 6.10
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
H2O
ADP
+
P
ATP
H+
Chemiosmosis
CONNECTION
6.11 Certain poisons interrupt critical events in cellular
respiration
Cyanide,
carbon monoxide
Rotenone
Block the movement of
electrons
H+
H+
H+
Block the flow of H+
through ATP synthase
Oligomycin
H+
H+
H
H+ H+ H+
Allow H+ to leak
through the membrane
+
ATP
Synthase
DNP
FADH2
FAD
1 O 2 + 2 H+
2
NAD+
NADH
H+
H+
H2O
ADP + P
ATP
H+
Electron Transport Chain
Figure 6.11
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Chemiosmosis
6.12 Review: Each molecule of glucose yields many
molecules of ATP (38)
Figure 6.12
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
6.13 Fermentation is an anaerobic alternative
to cellular respiration
• Under anaerobic conditions, many kinds of cells
– Can use glycolysis alone to produce
small amounts of ATP
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• In lactic acid fermentation
– NADH is oxidized to NAD+ as pyruvate is
reduced to lactate
2
NAD+
2
2
NADH
NADH
2
NAD+
GLYCOLYSIS
2 ADP + 2
P
2
ATP
2 Pyruvate
Glucose
Figure 6.13A
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2 Lactate
• In alcohol fermentation
– NADH is oxidized to NAD+ while
converting pyruvate to CO2 and ethanol
2
NAD+
2 NADH
2 NADH
NAD+
2
GLYCOLYSIS
2 ADP + 2 P
Glucose
2
2
ATP
CO2 released
2 Ethanol
2 Pyruvate
Figure 6.13B
Figure 6.13C
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INTERCONNECTIONS BETWEEN MOLECULAR
BREAKDOWN AND SYNTHESIS
• 6.14 Cells use many kinds of organic
molecules as fuel for cellular respiration
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• Carbohydrates, fats, and proteins can all fuel
cellular respiration
–
When they are converted to molecules that enter glycolysis or the citric
acid cycle
Food, such as
peanuts
Carbohydrates
Fats
Sugars
Glycerol
Proteins
Fatty acids
Amino acids
Amino
groups
Glucose
G3P
Pyruvate
Acetyl
CoA
GLYCOLYSIS
ATP
Figure 6.14
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
CITRIC
ACID
CYCLE
OXIDATIVE
PHOSPHORYLATION
(Electron Transport
and Chemiosmosis)
•
•
•
Proteins must first be digested to individual a____ acids.
Amino acids that will be catabolized must have their amino groups
removed via deamination.
The carbon skeletons are modified by enzymes and enter as
intermediaries into glycolysis or the citric acid cycle, depending on
their structure.
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
6.15 Intermediates from glycolysis and the citric
acid cycle are used as raw materials for making
complex organic
ATP needed to drive biosynthesis
ATP
substances
CITRIC
ACID
CYCLE
GLUCOSE SYNTHESIS
Acetyl
CoA
Pyruvate
G3P
Glucose
Amino
groups
Amino acids
Proteins
Fatty
acids Glycerol
Fats
Cells, tissues, organisms
Figure 6.15
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Sugars
Carbohydrates
6.16 The fuel for respiration ultimately comes from
photosynthesis
• All organisms
–
Can harvest energy from organic molecules
• Plants
–
make these molecules from inorganic sources
by the process of photosynthesis
Figure 6.16
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings