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Carbohydrate metabolism
Most carbs absorbed by the body are
monosacharides
glucose
galactose
fructose
Glucose is catabolized to CO2and H2O
energy released is used to make ATP
When we study ATP production,
we are studying carbohydrate metabolism
C6H12O6+ 6 O2--> 6 CO2+ 6 H2O + energy
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Respiration is the cumulative function of
glycolysis, the citric acid cycle, and electron transport
Glycolysis
occurs in the cytoplasm
generates a netof two molecules of ATP
citric acid cycle
occurs in the matrix of mitochondria generates two more ATP
Electron transport chain
occurs on the inner membrane of the mitochondria
generates about thirty-four ATP About 38 ATP molecules produced from one molecule of glucose
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Glycolysis harvests
chemical energy by
catabolizing glucose to
pyruvate
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Steps 1-3
two ATP hydrolyzed some oxygen and hydrogen rearranged
Step 4
6 carbon chain split
into twosmaller molecules
3 C each
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Step 5
a second Pi added to each 3 C chain
a high energy electron (w/ a H+)
carried off
NAD+ is a shuttle for electrons
carried to other parts of cell and
used for energy Step 6 and 7
Pi removed from
three carbon chain
used to synthesize ATP
end up with two moleculesof pyruvic acid
Gl l i
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Glycolysis
the final product of glycolysis is two
molecules of pyruvic acid
A total of 4 ATP and 2 NADH+H+are
produced from one glc. But since 2 ATP used to start the process,
you are only ahead two ATP and two
NADH+H+.
What happens next depends on if oxygen
is present.
No oxygen, use an NADH+H+to convert
each pyruvic acid to lactic acid
(anaerobic respiration).
But, if oxygen present, go to Citric Acid
cycle (aerobic respiration)
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Beforethe carbon chains can enter
citric acid cycle
converted to acetyl-CoA
For eachpyruvic acid one C lost as CO2
oneNADH+H+produced
Total of
two CO2 and two NADH+H+
from this rxn.
If oxygen present Citric Acid cycle
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If oxygen present Citric Acid cycle Remainingcarbons (2 C chain)
enter Citric Acid cycle
The two carbon Acetyl CoA
enters the Citric Acid cycle
and combines with a four carbon
oxaloacetic acid
to form a six carbon citric acid.
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As other reactions proceed,
two more CO2molecules are
produced for eachacetyl CoA that
entered the Citric Acid cycle. Plusone ATP,
three more NADH+H+,
andone FADH2
after both acetyl CoA moleculesgo through,
totals for Citric Acid cycle =
2 ATP,
6 NADH+H+,
and 2 FADH2
Oxaloacetic acid (four carbons) is
eventually recycled.
If oxygen present Citric Acid cycle
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from glycolysis
2 ATP (net)
2 NADH+H
+
from Citric Acid cycle
2 ATP
2+6 NADH+H+
2 FADH2
plus produced 6 CO2(three per pyruvic acid)
but:the ten NADH+H+
and the two FADH2
are now sent to the
electron transport chain
4 ATPs so far
- not too impressive
TOTALS SO FAR:
El t T t Ch i
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Electron Transport Chain 10 NADH+H+ and 2 FADH2produced during glycolysis
and citric acid cycle
each one of these contains chemical energy need to transfer this energy to ATP
ATP is used by all parts of the cell
NAD+and FAD need to be recycled
chains of enzymes onthe inner
mitochondrial
membrane are
responsible for this.
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Electron Transport Chain
-NADH+H+ hands off high energy e-to enzyme complex 1
-Energy from the e-is used to drive the proton pump that moves
H+ out of the mito.
-This begins to create a... H+(proton) gradient
The H+from
the NAD+
just mixes in
here.
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Electron Transport Chain
-enzyme complex 1 passes high energy e-to coenzyme Q
-coenzyme Q shuttles e-to enzyme complex 2
- Energy from the e-is used to drive the proton pump that moves
H+out of the mito.What does this help create??
H+gradient(proton
motive force)
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Electron Transport Chain
-enzyme complex 2 passes high energy e-to cytochrome c
- cytochrome c shuttles e-to enzyme complex 3
- Energy from the e-is used to drive the proton pump that moves
H+out of the mito.What does this help create??
H+gradient(proton
motive force)
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Electron Transport Chain
-by now, those electrons are not so high energy anymore...
- the low energy electrons combine back with hydrogen and are
finally added to an oxygen atom
- two hydrogen and one oxygen form water
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Electron Transport Chain
We still have not done anything with the H+gradient we created:
- H+runs down its concentration gradient to provide energy for
the enzyme ATP synthase
- ATP synthase uses the energy from the H+gradient to...
Convert
ADP + P
into ATP(oxidative
phosphoryl
ation)
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Electron Transport Chain
-Each NADH carries two electrons which pump out enough H+
to make 3 ATP molecules(10 NADH yield 30 ATP).
- Each FADH
carries two electrons but...-So each FADHonly pumps out enough H
+to make
2 ATP molecules(2 FADH yield 4 ATP).
FADH hands
off e-
here.
El T Ch i
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Electron Transport Chain
C6H12O6+ 6O2 6 CO2+ 6H2O
Inhale oxygen, exhale french fries
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Cellular
respiration
generates 36-38 ATP
molecules for
each sugarmolecule it
oxidizes
yco ys s an t e c tr c ac cyc e cyc e
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yco ys s an t e c tr c ac cyc e cyc econnect to many other metabolic pathways
Glycolysis receives by
metabolic by-products of...
carbohydrates
proteins
fats
Acetyl-CoA rxn. receives
metabolic by-products from
glycolysis
proteins
fats
Citric acid cycle receivesmetabolic by-products from
proteins
F db k h i t l
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Feedback mechanisms control
cellular respiration
Glycolysis is stimulated by high concentrations ofADP
Glycolysis is inhibited by high concentrations of
ATP, and citrate (from the citric acid cycle). Many enzymes throughout the respiratory cycle
are subject to feedback inhibition
feedback inhibition is when the product of a reactioninhibits the enzyme catalyzing the reaction