Chapter 8: Harvesting Energy: Glycolysis and Cellular Respiration

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Chapter 8Harvesting Energy Glycolysis and
Cellular Respiration
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Two Modes of Energy Acquisition

• Autotrophs Self-nourishing
• Photoautotrophs Carbon source is CO2 from the
  air and sunlight is the energy source that drives
  synthesis.
• Heterotrophs Feed on autotrophs.

3
The question that will be addressed

• How do cells release this acquired energy?

4
Two Main Types of Energy Releasing Pathways

• Aerobic Respiration Requires oxygen
• Starts in the cytoplasm
• Completed in mitochondrion
• Anaerobic Respiration Does not require oxygen.
• Starts in the cytoplasm
• Completed in the cytoplasm

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Two Pathways
start (glycolysis) in cytoplasm
start (glycolysis) in cytoplasm
completed in mitochondrion
completed in cytoplasm
Aerobic Respiration
Anaerobic Respiration
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Overview of Aerobic Respiration
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Aerobic Respiration Occurs in Three Stages

• 1. Glycolysis the breakdown of Glucose to 2
  molecules of Pyruvate
• Occurs in the Cytoplasm
• Results in the net production of 2 molecules of
  ATP and 2 molecules of NADH
• 2. The Krebs Cycle the breakdown of Pyruvate
  to CO2 and H2O
• Occurs in the Mitochondrion
• Results in the net production of 2 molecules of
  ATP, 8 NADH and 2 FADH2
• 3. Electron Transfer Phosphorylation generates
  ATP and H2O
• Occurs in the Mitochondrion
• Results in the net production of 32 molecules of
  ATP

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(cytoplasm)
C
C
C
C
C
C
glucose
ATP
2
Glycolysis
C
C
C
2
C
C
C
2
lactate
or
pyruvate
2
C
C

C
2
Fermentation
CO2
ethanol
2 CO2
C
Cellular respiration
C
C
C
4
CO2
2 acetyl CoA
Krebs cycle
ATP
2
electron carriers
Electron transport chain
ATP
32 or 34
intermembrane compartment
H2O
(mitochondrion)
O2
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Stage 1 Glycolysis

• Glycolysis is a 10 step reaction pathway
  catalyzed by 10 different enzymes.
• Occurs in the cytoplasm.
• Produces 4 molecules of ATP however it requires
  ATP for two of its steps. Net result 2 ATP
• Also produces 2 NADH

10
(cytoplasm)
C
C
C
C
C
C
glucose
ATP
2
Glycolysis
C
C
C
2
lactate
2
C
C
C
or
pyruvate
2
C
C

C
2
Fermentation
CO2
ethanol
2 CO2
C
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ATP
ADP
ATP
ADP
4
4
2
2
2
2
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
G3P
pyruvate
glucose
fructose bisphosphate
NAD
NADH
2
2
Energy harvest
Glucose activation
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1.
2.
3.
4.
DAP
PGAL
5.
PGAL
13
6.
7.
8.
9.
10.
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Stage 2 The Krebs Cycle
Pyruvate CO2 H2O

• The pyruvate produced in glycolysis is then
  shuttled into the Krebs Cycle.
• The Krebs Cycle is an 8 step cyclic reaction
  pathway catalyzed by 8 different enzymes.
• Occurs in the inner compartment of the
  mitochondrion.
• Produces 2 ATP, 8 NADH, and 2 FADH2

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Cellular respiration
C
C
C
CO2
4
2 acetyl CoA
Krebs cycle
2
ATP
electron carriers
Electron transport chain
ATP
32 or 34
intermembrane compartment
H2O
(mitochondrion)
O2
16
mitochondrion
inner membrane
intermembrane compartment
outer membrane
matrix
glucose
cristae
Glycolysis
2 pyruvate
coenzyme A
(intermembrane compartment)
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Formation of acetyl CoA
3
NADH
3
NAD
FAD
FADH2
C
CO2
coenzyme A
coenzyme A
_
C
C
CoA

Krebs cycle
C
C
C
C
CO2
2
acetyl CoA
pyruvate
NAD
NADH
ADP
ATP
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2 ATP 6 NADH, 2 FADH2
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Stage 3 Electron Transfer Phosphorylation

• The electrons carried by the NADH and FADH2 are
  then shuttled onto the electron transport chain.
• The transfer of electrons along the chain is
  accompanied by the pumping of Protons (H) from
  the matrix to the intermembrane compartment of
  the mitochondrion, which generates a
  proton/electrical gradient.
• Occurs in the inner mitochondrial membrane.
• These protons then flow down their concentration
  gradient back into the matrix generating 32-34
  ATP molecules in the process.
• The protons generate ATP by flowing through an
  ATP synthase.
• The electrons and Protons (H) are eventually
  used to reduce oxygen and generate water.

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(matrix)
FADH2
1/2 O2 2H
NADH
FAD
NAD
2e
2e
H2O
electron carriers
(inner membrane)
H
H
H
ATP
energy to drive
synthesis
(intermembrane compartment)
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H ion channel within ATP-synthesizing enzyme
(matrix)
electron transport chain
(inner membrane)
(intermembrane compartment)
(outer membrane)
(cytoplasm)
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H2O
2 H
1/2 O2
NAD
H
H
NADH
2e
H
H
H
23
H
ADP
ATP
(low H concentration)
H
H
H
(high H concentration)
H
H
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ATP
ATP
acetyl CoA
H
CO2
(cytoplasm)
H
H
ATP
ADP
Krebs cycle
(inner membrane)
H
H2O
1/2 O2
H
2e
H
2 H
H
(matrix)
energizedelectron carriers
H
CO2
Electron transport chain
2e
(outer membrane)
depleted carriers
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(cytoplasm)
C
C
C
C
C
C
glucose
ATP
2
Glycolysis
C
C
C
2
C
C
C
2
lactate
or
pyruvate
2
C
C

C
2
Fermentation
CO2
ethanol
2 CO2
C
Cellular respiration
C
C
C
4
CO2
2 acetyl CoA
Krebs cycle
ATP
2
electron carriers
Electron transport chain
ATP
32 or 34
intermembrane compartment
H2O
(mitochondrion)
O2
26
(No Transcript)
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Glycolysis followed by lactate fermentation
regeneration
NAD
NADH
NADH
NAD
C
C
2
2
C
C
C
C
C
C
C
C
C
C
(fermentation)
(glycolysis)
lactate
glucose
pyruvate
2
2
ATP
ADP
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Glycolysis followed by alcoholic fermentation
regeneration
NAD
NADH
NADH
NAD
2
C
C
C
C
C
2
C
2
C
C
C
C
C
C
(fermentation)
(glycolysis)
ethanol
CO2
glucose
pyruvate
2
ATP
2
ADP
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Alternative Energy Sources
FOOD
complex carbohydrates
glycogen
fats
proteins
simple sugars
fatty acids
glycerol
amino acids
glucose-6-phosphate

NH3
carbon backbones
GLYCOLYSIS
urea
PGAL
pyruvate
acetyl-CoA
KREBS CYCLE
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(cytoplasm)
complex carbohydrates
fats
proteins
glucose
amino acids
glycerol
Glycolysis
fatty acids
pyruvate
acetyl
CoA
Krebs cycle
electron carriers
Electron transport chain
synthesis
breakdown
(mitochondrion)
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The Circle of Life
sunlight energy
PHOTOSYNTHESIS
water carbondioxide
sugarmolecules
oxygen
AEROBICRESPIRATION