Download Chapter 7

CHAPTER 7
LECTURE
SLIDES
Prepared by
Brenda Leady
University of Toledo
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Cellular respiration
Process by which living cells obtain energy
from organic molecules
 Primary aim to make ATP and NADH
 Aerobic respiration uses oxygen

 O2

consumed and CO2 released
Focus on glucose but other organic
molecules also used
2
Glucose metabolism

1.
2.
3.
4.
C6H12O6 + 6O2 → 6CO2 + 6H2O
4 metabolic pathways
Glycolysis- Substrate level
phosphorylation
Breakdown of pyruvate to an acetyl group
Citric acid cycle
Oxidative phosphorylation
3
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1
Glycolysis:
Glucose
C C C C C C
Outer mitochondrial
membrane
Cytosol
2 pyruvate
2 C C C
2 NADH
Mitochondrial
matrix
Inner mitochondrial
membrane
2 NADH
2 pyruvate
2
Breakdown of
pyruvate:
2 pyruvate
2 C C C
2CO2 + 2acetyl
6 NADH 2 FADH2
3
Citric acid
cycle:
2 acetyl
4 Oxidative
2 C C
2 C C
2 CO2
2 CO2
+2 ATP
Via substrate-level
phosphorylation
2 acetyl
4 CO2
2 CO2
+2 ATP
Via substrate-level
phosphorylation
phosphorylation:
The oxidation of NADH
and FADH2 via the
electron transport
chain provides energy
to make more ATP
via the ATP synthase.
O2 is consumed.
+30–34 ATP
Via chemiosmosis
4
Stage 1: Glycolysis



Glycolysis can occur with or without
oxygen
Steps in glycolysis nearly identical in all
living species
10 steps in 3 phases
Energy investment
2. Cleavage
3. Energy liberation
1.
5
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6
3 phases of glycolysis
1.
Energy investment


2.
Cleavage


3.
Steps 4-5
6 carbon molecule broken into two 3 carbon
molecules of glyceraldehyde-3-phosphate
Energy liberation



Steps 1-3
2 ATP hydrolyzed to create fructose-1,6 bisphosphate
Steps 6-10
Two glyceraldehyde-3-phosphate molecules broken
down into two pyruvate molecules producing 2 NADH
and 4 ATP
Net yield in ATP of 2
7
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C C C C C C
CH2OH
O H
H
H
OH
H
HO
OH
H
OH
Glucose
8
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Energy investment phase
C C C C C C
C C C C C C
CH2OH
O H
H
H
OH
Step 2
Step 3
H
HO
OH
H
Step 1
OH
Glucose
P
OCH2
H
ATP
H
CH2O P
O
HO
OH
ATP
OH
H
Fructose-1,6bisphosphate
9
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Energy investment phase
Cleavage phase
C C C
H
Step 4
Step 5
C
O
CHOH
C C C C C C
C C C C C C
CH2O P
CH2OH
O H
H
H
OH
Step 2
Step 3
H
HO
OH
H
Step 1
OH
Glucose
P
OCH2
H
ATP
H
CH2O P
O
HO
OH
ATP
OH
H
Fructose-1,6bisphosphate
C C C
H
C
O
CHOH
CH2O P
Two molecules of
glyceraldehyde3-phosphate
10
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Energy investment phase
Cleavage phase
Energy liberation phase
C C C
C C C
O–
H
Step 4
Step 5
C
O
Step 6
Step 7
Step 8
Step 9
Step 10 C
O
C
O
CHOH
C C C C C C
C C C C C C
CH2O P
CH2OH
Pi
O H
H
H
OH
Step 2
Step 3
H
HO
OH
H
Step 1
OH
Glucose
P
OCH2
H
ATP
H
ATP
ATP
CH3
CH2O P
O
HO
OH
ATP
OH
NADH
H
Fructose-1,6bisphosphate
C C C
C C C
O–
H
C
O
CHOH
CH2O P
Pi
Two molecules of
glyceraldehyde3-phosphate
NADH
ATP
ATP
C
O
C
O
CH3
Two molecules
of pyruvate
11
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O–
C O
C O
Outer
CH3
membrane
channel
O–
H+/pyruvate
C O
symporter
H+
C O
CH3
+ CoA SH
+
NAD+
Pyruvate
dehydrogenase
S CoA
C O + CO2 + NADH
CH3
Acetyl CoA
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Stage 3: Citric acid cycle

Metabolic cycle
 Particular
molecules enter while other leave,
involving a series of organic molecules
regenerated with each cycle
Acetyl is removed from Acetyl CoA and
attached to oxaloacetate to form citrate or
citric acid
 Series of steps releases 2CO2, 1ATP,
3NADH, and 1 FADH2
 Oxaloacetate is regenerated to start the
cycle again

13
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Glycolysis:
Glucose
2 NADH
2 NADH
6 NADH
Citric
acid
cycle
2 pyruvate
2 CO2
2 CO2
Breakdown of
pyruvate
+2 ATP
2 FADH2
Oxidative
phosphorylation
NADH
CO2
2 CO2
+2 ATP
Citrate
+30–34 ATP
NADH
C C C C C C
C C C C C C
CO2
3
2
C C C C C
4
1
C C C C
Citric acid cycle
O
C C C C
5
Oxaloacetate
H2C C S CoA
Acetyl CoA
8
C C C C
7
NADH
6
C C C C
GTP
C C C C
ATP
FADH2
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Stage 4: Oxidative phosphorylation
High energy electrons removed from
NADH and FADH2 to make ATP
 Typically requires oxygen
 Oxidative process involves electron
transport chain
 Phosphorylation occurs by ATP synthase

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Oxidation: ETC

Electron transport chains (ETC)
 Group
of protein complexes and small organic
molecules embedded in the inner mitochondrial
membrane


Can accept and donate electrons in a linear
manner in a series of redox reactions
Movement of electrons generates H+
electrochemical gradient/ proton-motive force
 Excess
of positive charges outside of matrix
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KEY
H+ movement
e– movement
Matrix
Intermembrane
space
NADH dehydrogenase
NADH
I
H+
H+
H+
NAD+ + H+
Succinate
reductase
Q
Electron
transport
chain
H+
II
FADH2
FAD + 2
Ubiquinone
H+
H+
H- Cytochrome b-c1
III
H+
H+
Cytochrome c
c
H+
H+
2 H+ + ½ O2
IV
Cytochrome oxidase
H+
H+
H2O
H+
Matrix
H+
ATP synthase
H+
ADP + Pi
H+
ATP
Inner mitochondrial
membrane
ATP
synthesis
H+
Intermembrane
space
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Phosphorylation: ATP synthase
Lipid bilayer of inner mitochondrial
membrane relatively impermeable to H+
 Can only pass through ATP synthase
 Harnesses free energy release to
synthesize ATP from ADP
 Chemiosmosis- chemical synthesis of ATP
as a result of pushing H + across a
membrane

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NADH oxidation and ATP
synthesis
Oxidation of NADH results in
electrochemical gradient used to
synthesize ATP
 30-34 ATP molecules per glucose
molecule broken down into CO2 and H2O
 Rarely achieve maximal amount

 NADH
used in anabolic pathways
 H+ gradient used for other purposes
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ATP synthase




Enzyme harnesses free energy as H+ flow
through membrane embedded region
Energy conversion- H+ electrochemical gradient
or proton motive force converted to chemical
bond energy in ATP
Racker and Stoeckenius confirmed ATP uses an
H+ electrochemical gradient
Rotary machine that makes ATP as it spins
20
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21
Cancer cells usually favor
glycolysis





Many disease associated with alterations in
carbohydrate metabolism
Warburg effect- cancer cells preferentially use
glycolysis while decreasing oxidative
phosphorylation
Used to diagnose cancers in PET scans
Glycolytic enzymes overexpressed in 80% of all
types of cancers
Caused by genetic and environmental factorsmutations and low oxygen
Other organic molecules




Focus on glucose but other carbohydrates,
proteins and fats also used for energy
Enter into glycolysis or citric acid cycle at
different points
Utilizing the same pathways for breakdown
increases efficiency
Metabolism can also be used to make other
molecules (anabolism)
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Proteins
Amino
acids
Carbohydrates
Sugars
Fats
Glycerol Fatty
acids
Glycolysis:
Glucose
Glyceraldehyde3-phosphate
Pyruvate
Acetyl CoA
Citric
acid
cycle
Oxidative
phosphorylation
© The McGraw-Hill Companies, Inc./Ernie Friedlander/Cole Group/Getty Images
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Anaerobic metabolism
For environments that lack oxygen or
during oxygen deficits
 2 strategies

 Use
substance other than O2 as final electron
acceptor in electron transport chain
 Produce ATP only via substrate-level
phosphorylation
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Fermentation
Many organisms can only use O2 as final
electron acceptor
 Make ATP via glycolysis only
 Need to regenerate NAD+ to keep
glycolysis running
 Muscle cells produce lactate
 Yeast make ethanol
 Produces far less ATP

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2 ADP + 2 Pi
2 ATP
O—
2 ADP + 2 Pi
2 ATP
C O
C O
C O
C O
Glucose
Glycolysis
Glucose
CH3
Glycolysis
CH3
2 pyruvate
2 pyruvate
O—
2 NAD+ + 2 H+
2 NAD+ + 2 H+
2 NADH
C O
H
C OH
CH3
H
2 H1
2 lactate (secreted from the cell)
(a) Production of lactic acid
O—
2 NADH
2 CO2
H
H
C OH
C O
CH3
2 H+
2 ethanol (secreted from the cell)
CH3
2 acetaldehyde
(b) Production of ethanol
(weights): © Bill Aron/Photo Edit; (wine barrels): © Jeff Greenberg/The Image Works
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