Transcript Cellular Respiration

1
Overview:
Cellular respiration
is the process that
releases energy by
breaking down
food molecules in
the presence of
oxygen.
6O2 + C6H12O6
6H2O + CO2
+ energy
2
Fermentation:
The process
of releasing
energy in the
absence of
oxygen
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How much energy is in food?
• One calorie is the
amount of energy
needed to raise one
gram of water by 1
degree Celsius.
• One Calorie = one
kilocalorie (food
labels)
• One gram of sugar
yields 3811 calories of
heat energy
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Both processes begin with
glycolysis (anaerobic)
• The process in which one molecule of
glucose is broken in half, producing 2
molecules of pyruvic acid. (3-C compound)
• 2 ATPs are needed to start reaction, and 4
are produced, so there is a net gain of 2
ATP.
• Electrons are passed to NAD+ molecules
• Takes place in the cytoplasm
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Glycolysis
C6H12O6 +
NAD+
2 pyruvic
acids +
NADH
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Fermentation
• When oxygen is not
present, fermentation
releases energy from
food molecules.
• NADH is converted
back to NAD+ by
passing high energy
electrons to pyruvic
acid, allowing
glycolysis to continue.
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2 paths of fermentation
Alchoholic fermentation:
Yeasts and other
microorganisms use
pyruvic acid to form
ethyl alchohol and
CO2 and NAD+
Lactic Acid
Fermentation:
In some cells, such as
muscle cells, pyruvic
acid is converted to
lactic acid and NAD+
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Krebs Cycle (citric acid cycle)
• Pyruvic Acid is broken down to carbon
dioxide in a series (5 steps) of energyextracting reactions
• Takes place in the mitochondrial matrix
• CO2 is the by-product
• One glucose (2 turns of cycle) 
6 NADH + 2 FADH2 + 2 ATP + 4 CO2
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ELECTRON TRANSPORT CHAIN
• Takes place in cristae (inner mitochondrial membrane)
• 32 ATP produced in most eukaryotes; prokaryotes 34
• High-energy electrons (from NADH and FADH2 ) are
passed along a series of carrier proteins (ETC) until the end
where there is an enzyme that bonds the e-’s to hydrogen
ions and oxygen  water.
• The energy passed along the ETC is used to move H+ ions
into the intermembrane space.
• ATP synthase provides channels for H+ ions to pass
through.
• Each time it “rotates” an ADP and a P are attached.
• Aerobic respiration is about 40% efficient. The rest of the
energy is lost as heat.
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Energy and exercise
• Muscle cells normally
contain small amounts of
ATP, enough for a few
seconds of intense
activity
• Muscles use lactic acid
fermentation (about 90
sec) Extra oxygen is
needed to break it down.
• Glycogen is used for
about 20 minutes. Then,
stored molecules must be
broken down
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