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Cell Biology: Aerobic
respiration
How Cells Release
Stored Energy
Outline
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1. Key concepts
2. Definition of cellular respiration
3. The mechanism of cellular respiration
4. Energy flow
5. Conclusions
Key Concepts:
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All organisms can release energy stored in
glucose and other compounds, then use it in
ATP production
The initial breakdown reaction is called
glycolysis
Fermentation is an anaerobic process and
occurs in the cytoplasm
Aerobic respiration yields more energy from
glucose and occurs in the mitochondria
Key Concepts:
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Aerobic respiration has three stages
Photosynthesis and aerobic respiration are
linked on a global scale
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Sunlight -----> Photosynthesis
6CO2 + 6 H2O
Aerobic
Respiration
C6H12O6 + 6O2
Definition of cellular
respiration
A. Process by which organic compounds are
oxidized with the release of energy
B. Hydrolysis of ingested carbohydrate
polymers yields glucose
C. C6H12O6 + 6 O2  6 CO2 + 6 H2O + E(ATP + heat)
The mechanism of
cellular respiration
A.
1.
2.
3.
Glycolysis
Occurs in the cytoplasm
Anaerobic, not really a part of respiration
Glucose molecule  2 pyruvate
molecules (3-C)
4. 2 ATP used up, 4 ATP formed; 2 NADH
formed
5. Pyruvate and NADH enter mitochondria
(NADH- an electron carrier)
The mechanism of
cellular respiration
B. Krebs cycle (Citric Acid Cycle)
1. Acetyl-CoA formation
Pyruvate + CoenzymeA  Acetyl-CoA + CO2
2. Acetyl-CoA enters the Krebs cycle
a. glucose completely dismantled
b. CO2 produced
c. 2 ATP, 6 NADH and 2 FADH2
generated
The mechanism of
cellular respiration
C. Electron transport and ATP synthesis
There are a number of different proteins
involved in aerobic respiration that are embedded in
the inner membrane of the mitochondria. Some of
these proteins pick up and transport electrons in the
membrane and also pump H+ ions into the space
between the two membranes. Other proteins
embedded in the same membrane generate ATP by
allowing H+ ions to flow through them.
The Oxygen required for aerobic respiration is
used in electron transport to form H2O.
H+ gradient used to synthesis ATP: 3 ATP per
NADH and 2ATP per FADH2. 32 (34 in heart and
liver)ATP!
How Do Cells Make ATP?
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Photosynthesis
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Glycolysis
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Aerobic Pathways
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Anaerobic Pathways
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Fermentation
Overview of Aerobic Respiration
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Most ATP produced
Yield of 36 ATP or more
Summary
C6H12O6 + 6O2 ------> 6CO2 + 6 H2O
Glucose
Oxygen
Carbon
Dioxide
Respiration
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Glycolysis
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Krebs Cycle
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In cytoplasm
In mitochondria
Electron Transport
System
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In mitochondria
Glycolysis
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Glucose to Pyruvate
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2 ATP needed to
start process
End-Product
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2 molecules of
Pyruvate
Water
Second Stage of the Aerobic
Pathway
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Pyruvate in
mitochondria
Krebs Cycle
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Inner compartment
Electron Transport
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Inner membrane
Electron Transport
Phosphorylation
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In inner membrane
H+ concentration and
electrical gradients
ATP Synthases
Formation of ATP
from ADP
Electron Transport
Phosphorylation
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Anaerobic Routes of ATP
Formation
Fermentation
pathways
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Bacteria, yeasts and
Protistans
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Glycolysis - first
step
Net yield of two
ATP
Lactate or Alcohol
Lactate Fermentation
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Muscle cells in
animals
Quick ATP
Production
Some bacteria
Alcohol Fermentation
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Acetaldehyde
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Intermediate
product
Yeasts
Alternative Energy Sources in
the Human Body
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Carbohydrates
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Fats
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Production of ATP from metabolism
Excess stored as glycogen in liver and
muscle cells
Triglycerides
Stored in adipose tissue
Can be used for energy
Proteins
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Growth, maintenance, repair
Can be used for ATP production
The Energy Flow
Aerobic Respiration
Glycolysis
Krebs cycle
Electron transport
ATP synthesis
Starting Energy-carrying
Substance
glucose
Acetyl-CoA
NADH, FADH2
Products
ATP, NADH
Pyruvate
ATP, NADH,
FADH2, CO2
ATP, H2O
Where it occurs
Cytoplasm
Mitochondria
Matrix
Mitochondria
Inner Membrane
In Conclusion
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Aerobic respiration, fermentation, and other
pathways that release chemical energy produce
ATP
Glycolysis is the start to all the pathways
Aerobic respiration involves two more stages:
Krebs cycle and electron transport
Electron transport systems and ATP synthases
are embedded in the inner mitochondrial
membrane
In Conclusion
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H+ accumulate and gradients form across
the membrane
Energy released during H+ flow drives the
formation of ATP
Oxygen combines with H+ to form water
In humans and other mammals, sugars,
fats, and amino acids can enter the ATPproducing pathways