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Cellular Respiration
Cellular respiration: A catabolic energy yielding pathway
in which oxygen and organic fuels are consumed and ATP
is produced
• An aerobic process—it requires oxygen
Summary equations:
Organic
Compounds
+
Oxygen
Carbon + Water
Dioxide
+ Energy
Energy Conversion
Fuel rich in
chemical
energy
Energy conversion
Waste products
poor in chemical
energy
Heat
energy
Gasoline

Oxygen
Combustion
Kinetic
energy
of movement
Energy conversion in a car
Carbon dioxide

Water
Heat
energy
Food

Cellular
respiration
ATP
Carbon dioxide

Energy for cellular work
Oxygen
Water
Energy conversion in a cell
Cellular Respiration
•By oxidizing glucose, energy is taken out of “storage” and
made available for ATP synthesis
Oxidation
Glucose loses electrons
(and hydrogens)
C6H12O6
Glucose
 6
O2
Oxygen
6
CO2
Carbon
dioxide
 6
H 2O
Water
Reduction
Oxygen gains electrons (and hydrogens)
Metabolic Disequilibrium
*Multistep open hydroelectric system
Cellular Respiration
*Substrate-level
phosphorylation
3 metabolic stages:
*glycolysis *Krebs cycle
*electron transport chain and
oxidative phosphorylation
*Oxidative phosphorylation
Mitochondrion
Cytoplasm
Cytoplasm
Plant cell
Animal cell
Animal cell
Plant cell
Cytoplasm
Cytoplasm
Mitochondrion
Mitochondrion
High-energy
High-energy
electrons
electrons
carried
carried
NADH
bybyNADH
Glycolysis
Glycolysis2
Glucose Pyruvic
acid
2
ATP
ATP
High-energy
High-energy
electrons
carried
electrons carried
mainly
mainlyby
by
NADH
NADH
Citric
Citric
Electron
Acid
Electron
Acid
Transport
Cycle
Transport
Cycle
2
ATP
ATP
~34
ATP
ATP
~38 ATP
per
glucose
Figure 6.6
Cellular Respiration
Glycolysis harvests chemical energy by oxidizing glucose
to pyruvate.
Cellular Respiration
1) Glucose is
phosphorylated
3) Addition of another
phosphate group
2) G-6-P is
rearranged
5) Conversion b/w the 2
3-carbon sugars
4) Cleavage
into 2
3-carbon
sugars
Cellular Respiration
6) Two components:
*electron transfer
*Phosphate
group
addition
Glycolysis: Energy Payoff Phase
9) Loss of
water
7) ATP
production
8) Rearrangement
of phosphate group
10) ATP
production
Fermentation
aerobic
anaerobic
The Krebs cycle:
energy-yielding oxidation
Cellular
Respiration
The junction b/w glycolysis
and the Krebs cycle:
Multienzyme complex:
1) Removal of CO2
2) Electron transfer
*pyruvate dehydrogenase
3) Addition of CoA
Cellular Respiration
The Krebs cycle: energy-yielding oxidation
8) electron transfer
Malate dehydrogenase
1) Addition of 2 Carbons
Citrate synthase
2) Isomerization
Aconitase
7) Rearrangement
of bonds
Fumarase
6) electron transfer
Succinate
dehydrogenase
3) *Loss of CO2
*electron transfer
Isocitrate
dehydrogenase
4) *Loss of CO2
*electron transfer
a-ketoglutarate
dehydrogenase
5) substrate-level phosphorylation
Succinyl CoA-synthetase
Cellular Respiration
Electron transport and
ATP synthesis
*Multi-step open system
Cellular Respiration
Generation and maintenance of an H+ gradient
*Exergonic flow of e-, pumps H+ across the membrane
*chemiosmosis
high energy
electrons
Cellular Respiration
*How does the mitochondrion
couple electron transport and
ATP synthesis?
ATP synthase
Versatility of Cellular Respiration
– In addition to glucose, cellular respiration can “burn”:
• Diverse types of carbohydrates
• Fats
Food
• Proteins
Polysaccharides
Fats
Sugars Glycerol Fatty
acids
Glycolysis
Acetyl
CoA
ATP
Proteins
Amino acids
Citric
Acid
Cycle
Electron
Transport