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9-1 Chemical Pathways
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9-1 Chemical Pathways
9-1 Chemical Pathways
Food serves as a source of raw materials to build
cells in the body and as a source of energy.
Animal
Plant
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9-1 Chemical Pathways
Chemical Energy and Food
Chemical Energy and Food
●One gram of the sugar glucose (C6H12O6), when burned in
the presence of oxygen, releases 3811 calories (3.811 Cal)
of heat energy.
●What would happen to a cell when that energy is released
●
THE CELL WOULD BLOW UP!!!!!!!!!!!!!!!!!!!!
●Do you see a problem with this?
(A calorie is the amount of energy needed to raise the
temperature of 1 gram of water 1 degree Celsius.)
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9-1 Chemical Pathways
Chemical Energy and Food
●Cells don't “burn” glucose. Instead, they gradually
release the energy from glucose and other food
compounds AND….
●Transfer that energy in to other energy rich
molecules, like…
ATP
NADH and FADH2 (similar to NADPH)
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9-1 Chemical Pathways
Overview of Cellular Respiration
Cellular respiration is the process that
releases energy by breaking down
glucose and other food molecules in the
presence of oxygen.
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9-1 Chemical Pathways
Overview of Cellular Respiration
The equation for cellular respiration is:
6O2 + C6H12O6 → 6CO2 + 6H2O + Energy
oxygen + glucose → carbon dioxide + water + energy
●How is this equation similar to photosynthesis?
●What is the form of the energy? Is it light?
• NO!!!
It is ATP
●It turns out that each glucose can produce a total of about
38 ATP (36 net).
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Overview of Cellular Respiration
Each of the three stages of cellular respiration
captures some of the chemical energy available in
food molecules (glucose) and uses it to produce
ATP.
1.Glycolysis
2.Kreb’s cycle
3.Electron transport chain
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Overview of Cellular Respiration
Electrons carried in NADH
Electrons carried
in NADH and
FADH2
Pyruvic
acid
Glucose
Glycolysis
Cytoplasm
Mitochondrion
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9-1 Chemical Pathways
Overview of Cellular Respiration
Glycolysis takes place in the cytoplasm. The
Krebs cycle and electron transport take place in
the mitochondria.
Cell membrane
Glycolysis
Cytoplasm
Mitochondrion
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9-1 Chemical Pathways
Glycolysis
What happens during the process of
glycolysis?
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9-1 Chemical Pathways
Glycolysis
Glycolysis
Glycolysis is the process in which one molecule
of glucose is broken in half, producing two
molecules of pyruvic acid, a 3-carbon compound.
• Glycolysis releases a small amount of energy.
• glucose (6-C) becomes pyruvic acid (3-C) X2
• How many total carbon atoms are still present?
»6 carbons still present
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9-1 Chemical Pathways
Glycolysis
This gives the cell a net gain of 2 ATP molecules.
2 ATP
2 ADP
4 ADP
4 ATP
Glucose
2 Pyruvic
acid
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9-1 Chemical Pathways
Glycolysis
NADH Production
One reaction of glycolysis removes 4 high-energy
electrons, passing them to an electron carrier
called NAD+.
2 ATP
2 ADP
4 ADP
4 ATP
Glucose
2NAD+
2 Pyruvic
acid
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9-1 Chemical Pathways
Glycolysis
Each NAD+ accepts a pair of high-energy electrons
and becomes an NADH molecule—a high energy
molecule. The NADH molecule holds the electrons
until they can be transferred to other molecules.
2 ATP
2 ADP
4 ADP
4 ATP
Glucose
2NAD+
2
2 Pyruvic
acid
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9-1 Chemical Pathways
Glycolysis
Summarize what has been used and made…
ATP? NADH?
2 ATP
2 ADP
4 ADP
2NAD+
4 ATP
2
2 Pyruvic
acid
To the electron
transport chain
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9-1 Chemical Pathways
Glycolysis
The Advantages of Glycolysis
The process of glycolysis is so fast that cells can
produce thousands of ATP molecules in a few
milliseconds.
Glycolysis does not require oxygen.
*Disadvantage: only 2 ATP and 2 NADH; not
enough to “run” a multi-cellular organism
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9-1 Chemical Pathways
Fermentation
Fermentation
When oxygen is not present, glycolysis is followed
by a different pathway. The combined process of
this pathway and glycolysis is called fermentation.
Two types of fermentation:
1.Alcoholic fermentation
2.Lactic acid fermentation
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9-1 Chemical Pathways
Fermentation
The two main types of fermentation are
lactic acid fermentation and alcoholic
fermentation.
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Fermentation
The first part of fermentaition is glycolysis.
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Fermentation
The second part shows the conversion of pyruvic
acid to lactic acid (or ethanol and CO2). NAD+ is
regenerated for glycolysis to continue; get some
ATP
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Fermentation: Ethanol
formation
+1
CO2
ethanol
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The raw materials required for cellular
respiration are
a. carbon dioxide and oxygen.
b. glucose and water.
c. glucose and oxygen.
d. carbon dioxide and water.
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Glycolysis occurs in the
a. mitochondria.
b. cytoplasm.
c. nucleus.
d. chloroplasts.
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The net gain of ATP molecules after glycolysis is
a. 3 ATP molecules.
b. 2 ATP molecules.
c. 3 pyruvic acid molecules.
d. 4 pyruvic acid molecules.
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Fermentation releases energy from food
molecules in the absence of
a. oxygen.
b. glucose.
c. NADH.
d. alcohol.
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The first step in fermentation is always
a. lactic acid production.
b. the Krebs cycle.
c. glycolysis.
d. alcohol production.
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END OF SECTION