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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
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• 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
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
CO2
Breathing
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 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
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
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• 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
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
O2
STAGES OF CELLULAR RESPIRATION AND
FERMENTATION
• 6.6 Overview: Cellular respiration occurs in
three main stages
• Cellular respiration
– Occurs in three main stages
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• 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
• 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 prime a glucose
molecule
–
Which is split into two molecules of pyruvate
NAD+
2
2
NADH
+ 2
H+
Glucose
2 Pyruvate
2 ADP + 2
Figure 6.7A
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
P
2
ATP
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
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
ADP + P
• 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
+ H+
NADH
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
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Steps
+ H+
2and 3
NADH, ATP, and CO2 are
generated during redox
reactions.
NAD+
Steps
4and
5
Redox reactions generate
FADH2 and NADH.
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
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
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
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
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
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
INTERCONNECTIONS BETWEEN MOLECULAR
BREAKDOWN AND SYNTHESIS
• 6.14 Cells use many kinds of organic
molecules as fuel for cellular respiration
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• 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
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
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