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Biology, Seventh Edition
Solomon • Berg • Martin
Chapter 7
How Cells Make ATP:
Energy-Releasing
Pathways
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways
• Cellular respiration
• Aerobic respiration
–Requires molecular oxygen
–Includes redox reactions
• Anaerobic
–Anaerobic respiration
–Fermentation
–Do not require oxygen
• All exergonic
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways
• Four stages of aerobic
respiration
• Takes place in the cytosol
–Glycolysis
• Takes place in the mitochondrion
–Formation of acetyl CoA
–Citric acid cycle
–Electron transport chain/chemiosmosis
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways
Four stages of aerobic respiration
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways
Summary of aerobic respiration
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways
• Glycolysis
• “Sugar splitting”
• Does not require oxygen
• Divided into two major phases
–Energy investment phase
–Energy capture phase
• Each glucose molecule produces net
yield of two NADH molecules and two
ATP molecules
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways
Glycolysis
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways
Glycolysis:
energy investment
phase
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways
Glycolysis:
energy capture
phase
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways
• Formation of acetyl CoA
• Catalyzed by enzyme pyruvate
dehydrogenase
–First carboxyl group is split off as carbon
dioxide
–Then remaining two-carbon fragment is
oxidized and electrons transferred to
NAD+
–Finally, oxidized two-carbon group is
attached to coenzyme A
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways
Formation
of acetyl CoA
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways
• Citric acid cycle
• For every glucose, two acetyl groups
enter the citric acid cycle
• Each two-carbon acetyl group
combines with a four-carbon
compound
• Two CO2 molecules are removed
• Energy captured as one ATP, three
NADH, and one FADH2 per acetyl
group
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways
Citric acid cycle
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways
Detail of
citric acid cycle
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways
• Electron transport chain
• Series of electron carriers
• Each carrier exists in oxidized or
reduced form
• Electrons pass down the electron
transport chain in series of redox
reactions
• Lose energy as pass along the chain
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways
Electron transport chain
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways
Accumulation
of protons within
the inter-membrane
space
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways
Electron transport and chemiosmosis
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways
Energy
yield from
complete
oxidation of
glucose by
aerobic
respiration
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways
• Many organisms depend on
nutrients other than glucose
• Products of protein and lipid
catabolism enter same
metabolic pathways as glucose
• Amino acids are deaminated
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways
Energy
from
carbohydrates,
proteins, and fats
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways
• Anaerobic respiration versus
fermentation
• Anaerobic respiration
–Electrons transferred from fuel molecules
to electron transport chain
–Final electron acceptor is inorganic
substance
• Fermentation
–Anaerobic process that does not use
electron transport chain
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways
Comparison of aerobic respiration,
anaerobic respiration, and fermentation
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways
Fermentation
Copyright © 2005 Brooks/Cole — Thomson Learning
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