1. Cellular Metabolism Chapter 4
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2. Cellular Respiration Occurs in a series of reactions: Glycolysis
Citric acid cycle (Kreb’s Cycle)
Electron transport chain (ETC)

3. Cellular Respiration Produces: Carbon dioxide Water
ATP (chemical energy)
Heat
Includes:
Anaerobic reactions (without O2) - produce little ATP
Aerobic reactions (requires O2) - produce most ATP

4. Glycolysis Sugar splitting Series of ten reactions
Breaks down glucose into 2 pyruvic acid molecules
Occurs in cytosol (cytoplasm)
Anaerobic phase of cellular respiration
Yields two ATP molecules per glucose molecule
Summarized by three main phases or events:
Phosphorylation
Splitting
Production of NADH and ATP

5. Glycolysis Event 1 – Phosphorylation Two phosphates added to glucose
Requires ATP
Phase 1
priming
Phase 2
cleavage
Phase 3
oxidation and
formation of
ATP and release
of high energy
electrons
2 ADP
2 NADH + H+
2 NAD+ P
ATP
Glyceraldehyde
phosphate
Glucose
Dihydroxyacetone 2
4 ADP 4
Fructose-1,6-diphosphate O2
2 Pyruvic acid
2 Lactic acid
To citric acid cycle
and electron transport
chain (aerobic pathway)
Carbon atom
Phosphate
Event 2 – Splitting (cleavage)
6-carbon glucose split into two 3-carbon molecules

6. Glycolysis
Event 3 – Production of NADH (nicotinamide adenine dinucleotide hydride or coenzyme 1) and ATP
Hydrogen atoms are released
Hydrogen atoms bind to NAD+ to produce NADH
NADH delivers hydrogen and high energy electrons to electron transport chain if oxygen is available
ADP (adenosine diphosphate) is phosphorylated to become ATP
Two molecules of pyruvic acid are produced
Two molecules of ATP are generated
Phase 1
priming
Phase 2
cleavage
Phase 3
oxidation and
formation of
ATP and release
of high energy
electrons
2 ADP
2 NADH + H+
2 NAD+ P
ATP
Glyceraldehyde
phosphate
Glucose
Dihydroxyacetone 2
4 ADP 4
Fructose-1,6-diphosphate O2
2 Pyruvic acid
2 Lactic acid
To citric acid cycle
and electron transport
chain (aerobic pathway)
Carbon atom
Phosphate

7. Anaerobic Reactions If oxygen is not available (Fermentation):
Electron transport system cannot accept new electrons from NADH
Pyruvic acid is converted to lactic acid or ethanol (for yeast and bacteria)
Glycolysis is inhibited
ATP production is less than in aerobic reactions
Phase 1
priming
Phase 2
cleavage
Phase 3
oxidation and
formation of
ATP and release
of high energy
electrons
2 ADP
2 NADH + H+
2 NAD+ P
ATP
Glyceraldehyde
phosphate
Glucose
Dihydroxyacetone 2
4 ADP 4
Fructose-1,6-diphosphate O2
2 Pyruvic acid
2 Lactic acid
To citric acid cycle
and electron transport
chain (aerobic pathway)
Carbon atom
Phosphate

8. Aerobic Reactions If oxygen is available:
Pyruvic acid is used to produce acetyl CoA
Citric acid cycle begins
Electron transport chain functions
Carbon dioxide and water are formed
Up to 38 molecules of ATP are produced per each glucose molecule
ATP 2
Glucose
Pyruvic acid
Acetyl CoA
CO2
2 CO
Citric acid O H 2e –
+ 2H +
Electron transport chain
32-34
Cytosol
Mitochondrion
High energy
electrons (e–) and
hydrogen ions (H+)
hydrogen ions (h+)
Oxaloacetic
acid
High energy electrons (e–) and hydrogen ions (H+)

9. Citric Acid Cycle
Begins when acetyl CoA combines with oxaloacetic acid to produce citric acid
Citric acid is changed into oxaloacetic acid through a series of reactions
Cycle repeats as long as pyruvic acid and oxygen are available
Citric acid cycle
ADP +
ATP
Pyruvic acid from glycolysis
Citric acid
(start molecule)
Acetyl CoA
(replenish molecule)
Acetic acid
Oxaloacetic acid
(finish molecule)
Isocitric acid CO 2
Succinyl-CoA
Succinic acid
FAD
FADH
Fumaric acid
Malic acid
Cytosol
Mitochondrion
NADH + H +
NAD
CoA P
Carbon atom
Phosphate
Coenzyme A
-Ketoglutaric acid
For each citric acid molecule:
One ATP is produced
Eight hydrogen atoms are transferred to NAD+ and FAD (Flavin adenine dinucleotide)
Two CO2 produced

10. Electron Transport Chain
NADH and FADH2 carry hydrogen and high energy electrons to the ETC
ETC is a series of enzyme complexes located in the inner membrane of the mitochondrion (the matrix)
Energy from electrons transferred to ATP synthase
ATP synthase catalyzes the phosphorylation of ADP to ATP
Water is formed (Oxygen is the final electron “carrier”)
ATP
ADP +
ATP synthase
Electron transport chain
Energy P
2H+
+ 2e–
2e–
NADH + H+
NAD+
FADH2
FAD O 2
H2O

11. Summary of Cellular Respiration (page 81)
Glycolysis
Cytosol
Mitochondrion A T P 2
Glucose
High-energy electrons (e–) 2e –
and 2H + H O
32–34 CO
Pyruvic acid
2 CO
Acetyl Co
Citric acid
Oxaloacetic acid 1 3 4
The 6-carbon sugar glucose is broken down in the cytosol into two 3-carbon pyruvic acid molecules with a net gain of 2 ATP and release of high-energy electrons.
Citric Acid Cycle
The 3-carbon pyruvic acids generated by glycolysis enter the mitochondria. Each loses a carbon (generating CO2 and is combined with a coenzyme to form a 2-carbon acetyl coenzyme A (acetyl CoA). More high-energy electrons are released.
Each acetyl CoA combines with a 4-carbon oxaloacetic
acid to form the 6-carbon citric acid, for which the cycle
is named. For each citric acid, a series of reactions
removes 2 carbons (generating 2 CO2’s), synthesizes
1 ATP, and releases more high-energy electrons.
The figure shows 2 ATP, resulting directly from 2
turns of the cycle per glucose molecule that enters
glycolysis.
Electron Transport Chain
The high-energy electrons still contain most of the
chemical energy of the original glucose molecule.
Special carrier molecules bring the high-energy electrons to a series of enzymes that convert much of the remaining energy to more ATP molecules. The other products are heat and water. The function of oxygen as the final electron acceptor in this last step is why the overall process is called aerobic respiration.
Electron
transport
chain
cycle

12. Carbohydrate Storage Carbohydrate molecules from foods can enter:
Catabolic pathways for energy production
Anabolic pathways for storage

13. Carbohydrate Storage Excess glucose stored as:
Glycogen (primarily by liver and muscle cells)
Fat
Converted to amino acids
Hydrolysis
Monosaccharides
Energy + CO2 + H2O
Glycogen or Fat
Amino acids
Carbohydrates
from foods
Catabolic
pathways
Anabolic

14. Summary of Catabolism of Proteins, Carbohydrates, and Fats (page 83)
High energy
electrons carried
by NADH and FADH2
Breakdown of simple
molecules to acetyl
coenzyme A
accompanied by
production of limited
ATP and high energy
electrons
H2O
2e– and 2H+
Waste products
–NH2
CO2
Citric
acid
cycle
Electron
transport
chain
Amino acids
Acetyl coenzyme A
Simple sugars
(glucose)
Glycerol
Fatty acids
Proteins
(egg white)
Carbohydrates
(toast, hashbrowns)
Food
Fats
(butter)
Pyruvic acid
ATP
Breakdown of large
macromolecules
to simple molecules
Glycolysis 1 2 3
© Royalty Free/CORBIS.
½ O2
Complete oxidation
of acetyl coenzyme A
to H2O and CO2 produces
high energy electrons
(carried by NADH and
FADH2), which yield much
ATP via the electron
transport chain