Download Cellular Respiration & Fermentation

Chapter 6
How Cells Harvest Chemical
Energy
PowerPoint Lectures for
Biology: Concepts and Connections, Fifth Edition
– Campbell, Reece, Taylor, and Simon
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
How Is a Marathoner Different from a Sprinter?
• Human muscles contain two different types of
muscle fibers
–
That perform differently under different
conditions
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• The different types of muscle fibers
– Function either aerobically, with oxygen,
or anaerobically, without oxygen
• Cellular respiration
– Is the process by which cells produce
energy aerobically
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
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• Photosynthesis uses solar energy
–
To produce glucose and O2 from CO2 and H2O
Sunlight energy
ECOSYSTEM
Photosynthesis in
chloroplasts
CO2
Glucose
+
+
H2O
O2
Cellular respiration in
mitochondria
ATP
(for cellular work)
Heat energy
Figure 6.1
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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
CO2
Breathing
Lungs
CO2
Bloodstream
O2
Muscle cells carrying out
Cellular Respiration
Glucose + O2
Figure 6.2
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CO2 + H2O + ATP
6.3 Cellular respiration banks energy in ATP
molecules
• Cellular respiration breaks down glucose
molecules
– And banks 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
CONNECTION
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
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• 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
O
NAD+
O + 2H
H
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
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• 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
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ATP
Oxidative
phosphorylation
6.7 Glycolysis harvests chemical energy by oxidizing
glucose to pyruvate
• In glycolysis, ATP is used to prime 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
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+2
P
2
ATP
• Glycolysis produces ATP by substrate-level
phosphorylation
–
In which a phosphate group is transferred
from an organic molecule to ADP
Enzyme
P
P
P
Adenosine
ADP
ATP
P
Organic molecule
(substrate)
Figure 6.7B
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P
• 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
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6.8 Pyruvate is chemically groomed for the 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)
6.9 The citric acid cycle completes the oxidation of organic
fuel, generating many NADH and FADH2 molecules
• In the citric acid cycle
–
The two-carbon acetyl part of acetyl CoA is
oxidized
Acetyl CoA
CoA
CoA
CITRIC ACID CYCLE
2 CO2
3 NAD+
FADH2
3 NADH
FAD
+
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
–
Two CO2 molecules are released
–
The energy yield is one ATP, three NADH,
and one FADH2
CoA
Acetyl CoA
CoA
2 carbons enter cycle
Oxaloacetate
1
Citrate
NADH + H
+
NAD+
5
CO2 leaves cycle
2
CITRIC ACID CYCLE
NAD+
+
NADH + H
Malate
ADP + P
FADH2
4
ATP
FAD
Alpha-ketoglutarate
3
CO2 leaves cycle
Succinate
NADH
Step
1
Acetyl CoA stokes the furnace.
Figure 6.9B
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Steps
+ H+
NAD+
2and 3
NADH, ATP, and CO2 are
generated during redox
reactions.
Steps
4and
5
Redox reactions generate
FADH2 and NADH.
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
NADH
FAD
NAD+
+
H
Mitochondrial
matrix
1O
+ 2 H+
2 2
H+
H+
H2 O
Electron Transport Chain
OXIDATIVE PHOSPHORYLATION
Figure 6.10
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ADP
+
P
H+
ATP
Chemiosmosis
CONNECTION
6.11 Certain poisons interrupt critical events in cellular
respiration
• Various poisons
–
Block the movement of electrons
–
Block the flow of H+ through ATP synthase
–
Allow H+ to leak through the membrane
Cyanide,
carbon monoxide
Rotenone
H+
H+
+
Oligomycin
H+
+
H
H
H+ H+ H+
H+
ATP
Synthase
DNP
FADH2
FAD
1 O2 + 2 H+
2
+
NADH
NAD
H+
H+
H+
Figure 6.11
Electron Transport Chain
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H2O
ADP + P
ATP
Chemiosmosis
6.12 Review: Each molecule of glucose yields many
molecules of ATP
• Oxidative phosphorylation, using electron transport and
chemiosmosis
–
Produces up to 38 ATP molecules for each
glucose molecule that enters cellular respiration
Electron shuttle
across membrane
Cytoplasm
Mitochondrion
2 NADH
2 NADH
(or 2 FADH2)
2 NADH
GLYCOLYSIS
2
Glucose
Pyruvate
2 Acetyl
CoA
+ 2 ATP
by substrate-level
phosphorylation
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CITRIC ACID
CYCLE
+ 2 ATP
by substrate-level
phosphorylation
Maximum per glucose:
Figure 6.12
6 NADH
About
38 ATP
2 FADH2
OXIDATIVE
PHOSPHORYLATION
(Electron Transport
and Chemiosmosis)
+ about 34 ATP
by oxidative phosphorylation
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
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• 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
GLYCOLYSIS
Acetyl
CoA
ATP
Figure 6.14
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
CITRIC
ACID
CYCLE
OXIDATIVE
PHOSPHORYLATION
(Electron Transport
and Chemiosmosis)
6.15 Food molecules provide raw materials for
biosynthesis
• Cells use some food molecules and intermediates
from glycolysis and the citric acid cycle as raw
materials
• This process of biosynthesis
ATP needed to drive biosynthesis
ATP
–
Consumes ATP
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, but not animals
–
Can also make these molecules from inorganic
sources by the process of photosynthesis
Figure 6.16
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings