CO2 + H2O
Photosynthesis
(plants, algae, cyanobacteria)
C6H12O6 + O2
Cellular Respiration
(Eukaryotic cells)
CO2 + H2O
Cellular Respiration (requires O2 and gives off CO2)
 Breakdown of glucose in the presence of oxygen to yield large amounts of
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


ATP
Occurs in the cytoplasm and mitochondria of eukaryotic cells
C6H12O6 + 6O2  6CO2 + 6H2O + (36 ATP) (what is oxidixed?reduced?)
Exergonic reaction- high energy molecule, glucose, produces low energy
molecules; 39% efficient
What do cells do with the ATP?
Cellular Respiration Occurs in 4 Phases
 Stage I: Glycolysis
(cytoplasm)
 Stage II: Prep Stage
(mitochondrial
matrix)
 Stage III: Citric Acid
Cycle (mitochondrial
matrix)
 Stage IV: Electron
Transport Chain 
oxidation- reduction
reactions using
NADH, FADH2
(mitochondrial
cristae)
Stage I: Glycolysis
 Ancient universal reaction
 Breakdown of glucose 2


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
pyruvates
Occurs in the cytoplasm;
outside of mitochondria
Anaerobic
Requires an initial energy (2
ATPs) investment
4 ATPs are made by
substrate level
phosphorylation (ATP
synthesis)
Net Yield: 2 ATPs, 2 NADHs
Substrate level
ATP synthesis;
coupled reactions
NAD+ = redox coenzyme,
carries electrons to ETC
when O2 is available and
is reused.
When O2 is not available
fermentation occurs, with a
net yield of 2 more ATP
Substrate
level ATP
synthesis
Substrate
level ATP
synthesis
Stage II:
Prep Stage
 Pyruvate  Acetyl
CoA
 Occurs in the
mitochondria
(matrix)
 Releases 2 CO2
 Makes 2 NADH
Stage III:
Citric Acid
Cycle
 A circular enzyme driven




metabolic pathway that
generates coenzymes
and ATP
Occurs in the
mitochondria (matrix)
Starts with the
combination of
oxaloacetate + Acetyl
CoA  citrate
2 turns = 2 ATPs, 6
NADH, 2 FADH2 are
made
4 CO2 are released;
Glucose has been
converted to 6 CO2- 2 in
prep, 4 in Citric acid
cycle
Substrate level
ATP synthesis
Stage IV: Electron
Transport Chain
(ETC)
 Movement of electrons
through a series of
coenzyme/protein redox
reactions to yield large
amounts of ATP; electrons
fall from hydrogen to
oxygen releasing energy
 Electrons (e-) are donated
from NADH, FADH2 to
the ETP
 As, e- move through the
ETP, they attract H+ ions
to the outer compartment
of mitochondria
Stage IV: ETC
and
Chemiosmosis
 A electrical and H+ concentration


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
gradient is created (10x)
H+ ions must move back from a
higher lower concentration
Only return to inner
compartment through ATP
synthases, “gates of the dam”
As they move through, activate
ATP synthase to make ATP from
ADP + Pi
This process is called
Chemiosmosis (ATP production
linked to H+ gradient)
 1 minute reserve of ATP
Stage IV-ETC
 The coenzymes NADH and FADH2 give up
electrons to the ETP
 The higher up in the ETP, the more energy
released by those e 1 NADH = 3 ATP, 1 FADH2 = 2 ATP
 The final electron acceptor is O2, which combines
with H+ ions to form H2O
 How many ATPs are made through the ETC?
Total ATP Yield during Cellular Respiration:
Molecular Bookkeeping
 Glycolysis: 2 NADH, 2 ATP
 Prep stage: 2 NADH
 Citric Acid Cycle: 6 NADH, 2
FADH2, 2 ATP
 ETC: 34 ATP (but, substract 2
ATP from total to account for
NADH brought in from
cytoplasm) = 32 ATP net
 ATP yield from the
complete breakdown of 1
glucose = 36 ATP
 38 ATP in liver, heart, kidney
cells
Anaerobic Respiration: A Comparison to
Aerobic Respiration
Anaerobic respiration
Cellular respiration
 Breakdown of glucose
 Breakdown of glucose
 No oxygen required
 Oxygen required
 Low ATP yield
 High ATP yield
 Quick energy yield
 Slow energy yield
 Starts and finishes in
 Starts in cytoplasm
cytoplasm
 Finishes in mitochondria
 Bacteria, muscle, yeast cells  Animal, plant cells
Anaerobic Respiration:
Lactic Acid Fermentation
 Pyruvate  lactate + 2 ATP
 Occurs in absence of O2
 Lactobacillus (dairy
products) and muscle cells
 Quick, low energy yield
 Wastes glucose, pyruvate
cannot enter into Citric Acid
Cycle
Anaerobic Respiration:
Alcoholic Fermentation
 Pyruvate  ethanol + CO2
 Occurs in absence of O2
 Low ATP yield, wastes
pyruvate (glucose)
 Yeast cells (baking) and
production of beer and wine
Metabolic Pool
Concept
 Human diet consists of other
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macromolecules such as proteins and
fats. What happens to them?
Which of the biomolecules gives the cell
the most ATP when completely broken
down?
How much ATP would be made from a
18 carbon fatty acid? 9 Acetyl CoA?
Catabolism  degradation
Anabolism  synthesis
Compare and Contrast Photosynthesis
to Cellular Respiration