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 (releases energy…
spontaneous…downhill reaction)
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways
What Type of Process is Cellular
Respiration?
• An Oxidation-Reduction Process
or REDOX Reaction
• Oxidation of GLUCOSE --> CO2 +
H2O (e- removed from C6H12O6)
• Reduction O2 to H2O (e- passed
to O2)
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways
What Carries the Electrons?
• NAD+
•
•
(nicotinadenine
dinucleotide) acts
as the energy
carrier
NAD+ is a
coenzyme
It’s Reduced to
NADH when it
picks up two
electrons and one
hydrogen ion
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways
Are There Any Other Electron
Carriers?
• YES! Another
Coenzyme!
• FAD+ (Flavin
adenine
dinucleotide)
• Reduced to
FADH2
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways
Other Cellular Respiration Facts
• Metabolic Pathway that breaks
down carbohydrates
• Process is Exergonic as Highenergy Glucose is broken into
CO2 and H2O
• Process is also Catabolic
because larger Glucose breaks
into smaller molecules
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways
Review of Mitochondria
Structure
• Smooth outer
Membrane
• Folded inner
membrane
• Folds called
Cristae
• Space inside
cristae called the
Matrix
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways
What are the Stages of
Cellular Respiration?
• Glycolysis
• Formation of acetyl Co-A
• The Krebs Cycle
• The Electron Transport Chain
Copyright Cmassengale
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
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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”
Occurs in the cytosol
Does not require oxygen (anaerobic)
Divided into two major phases
–Energy investment phase
–Energy capture phase
• 1 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
Energy investment
• Phosphorylation occurs2 ATP molecules
transfer a phosphate to a
G3P sugar
Energy Capture
• 4 ATP molecules and 2
NADH
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
•Catalyzed by the
multienzyme complex
pyruvate dehydrogenase
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways
• Citric acid cycle (Krebs Cycle)
• For 1 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 (These
will act as energy carriers for the electron
transport chain)
**So… 2 acetyl groups yields 4 CO2, 6
NADH, 2 FADH2, 2 ATP
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways
Citric acid cycle
• Also known as the
Krebs Cycle
• Because 1 glucose
produces 2 acetyl
CoA molecules two
cycles are required
per glucose
• After 2 turns the
original glucose can
be said to have been
completely
consumed
• **So… 2 acetyl
groups yields 4 CO2,
6 NADH, 2 FADH2, 2
ATP
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
A Little Krebs Cycle History
• Discovered by
Hans Krebs in
1937
• He received the
Nobel Prize in
physiology or
medicine in 1953
for his discovery
• Forced to leave
Germany prior to
WWII because he
was Jewish
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
• Released energy is used to pump protons
across the inner membrane space
(Hydrogen ions=protons)
• Oxygen is the final electron acceptor
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways
Electron Transport Chain Summary
• 34 ATP Produced
• Oxygen is the final electron acceptor
• H2O Produced
• Occurs Across Inner Mitochondrial
membrane
• Uses coenzymes NAD+ and FAD+ to
accept e- from glucose
• NADH = 3 ATP’s
• FADH2 = 2 ATP’s
Copyright Cmassengale
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
Energy from
the energy
carriers is
used to
move the
H+ ions
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways
Electron Transport Chain Animation
Copyright Cmassengale
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
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Biology, Seventh Edition
CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways
What if Oxygen is not Available
• Anaerobic respiration takes
place
• Not as efficient as aerobic
respiration
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Biology, Seventh Edition
CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways
Fermentation
 Occurs when O2 NOT present (anaerobic)
Called Lactic Acid fermentation in muscle cells (makes
muscles tired)
Temporary and 80% of the lactate will be exported
to liver and regenerated into more glucose for muscle
cells
Called Alcohol fermentation in yeast (produces
ethanol)
Basis for production of beer, wine, and makes
bread dough rise
Nets only 2 ATP
Copyright Cmassengale
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
•Amino acids can have
an amine group
removed by
demamination and
converted to
urea…leaving the
carbon chain to be
metabolized
•Lipids will generate 44
ATP
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