Slide # 2
Cells Need Energy
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Section:
1. Organisms obtain energy from food
2. Glucose is main source of food for cells
3. Cells break chemical bonds of glucose;
energy released
4. Energy is stored in ATP
5. Making ATP is part of cellular respiration
Respiration
Cellular Respiration
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If cellular respiration took place in just one
step:
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All of the energy would be released at once
Most would be lost in the form of light and heat.
Instead, a living cell has to release chemical
energy in food molecules a little bit at a time.
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Must trap those little bits of energy by using
them to make ATP.
Cellular Respiration
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Cellular Respiration - Process that
releases energy by breaking down
glucose and other food molecules in
the presence of oxygen
Cellular Respiration
Requires (Reactants):
1.
2.
Glucose
Oxygen
Gives Off (Products):
1.
2.
3.
Water
Carbon Dioxide
Energy
3 Stages of Cellular
Respiration
1.
2.
3.
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Glycolysis
Krebs Cycle
Electron Transport
Chain
Each stage
captures some of
the chemical
energy available in
food molecules
and uses it to
produce ATP.
First Stage: Glycolysis
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Glycolysis –A molecule of glucose is
broken into two molecules of pyruvic
acid.
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Occurs in the cytoplasm
Does not require oxygen (anaerobic)
1 Glucose
C-C-C-C-C-C
2 Pyruvic Acid
C-C-C
C-C-C
Glycolysis
Glucose
C-C-C-C-C-C
2 ATP
2 ADP
C-C-C
TO THE
ELECTRON
TRANSPORT
CHAIN
C-C-C
2 NAD+
4 ADP
2 NADH
4 ATP
2 Pyruvic Acid
C-C-C C-C-C
Products of Glycolysis
1.
2.
3.
NET Gain 2 ATP (Major Energy molecule)
2 NADH (Minor Energy molecule)
2 Pyruvic Acid Molecules
http://www.youtube.com/watch?v=C78BMJ7D68I (Glucose – Sugar Sugar Song)
Glycolysis
Anaerobic
(no oxygen)
Fermentation
Aerobic
(oxygen)
Krebs Cycle
Second Stage: Fermentation
or Krebs Cycle
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Glycolysis can be followed by
fermentation or the Krebs cycle
depending if oxygen is present.
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Fermentation will occur if no oxygen is
present.
Krebs Cycle will occur if oxygen is
present.
Second Stage: Fermentation
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Fermentation - Releases energy from
food molecules by producing ATP in
the absence of oxygen.
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Anaerobic - Does not require oxygen
Occurs in the cytoplasm (cytosol)
Fermentation
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Two types of Fermentation:
1.
2.
Alcoholic Fermentation
Lactic Acid Fermentation
Alcoholic Fermentation
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Produces:
1.
2.
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Examples:
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Ethyl alcohol
Carbon dioxide
Used to produce beer and wine
Causes bread dough to rise
Carried out by yeasts and a few other
microorganisms
Lactic Acid Fermentation
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Produces:
1.
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Examples:
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Lactic Acid
Produced in your muscles during rapid exercise
Buildup of lactic acid causes a painful, burning
sensation…why muscles feel sore
Used in production of cheese, sour cream, yogurt,
and pickles.
Carried out by animals and some unicellular
prokaryotes (bacteria).
At the End of Glycolysis
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90% of the chemical energy that was
available in glucose is still unused
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Locked in the high-energy electrons of pyruvic
acid
Oxygen is required for the final steps of
cellular respiration.
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Oxygen is the world's most powerful electron
acceptor.
Therefore, cellular respiration is aerobic
(requires oxygen).
Second Stage: Krebs Cycle
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Krebs Cycle Pyruvic acid is
broken down into
carbon dioxide in a
series of energyextracting
reactions.
Occurs in the
mitochondrion.
Krebs Cycle
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Starts: Pyruvic Acid
Produces: Carbon Dioxide
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Source of all the carbon dioxide in your breath.
Energy Tally - Each Molecule of Pyruvic
Acid Produces:
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1 ATP (and NADH/FADH2)
All energy molecules!
Third Stage: Electron
Transport Chain
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The electron transport chain uses the
high-energy electrons from the Krebs
cycle to convert ADP into ATP.
Oxygen serves as the final electron
acceptor.
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Occurs in the mitochondrion.
ATP
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Glycolysis: 2 ATP
molecules per glucose
molecule
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Needs 2 ATP (Investment)
Produces 4 ATP
Net gain of 2 ATP
molecules.
Krebs Cycle and Electron
Transport: 34 ATP
molecules per glucose
molecule
Total = 36 ATP
Black eyed peas review
respiration song
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http://www.youtube.com/watch?v=3aZr
kdzrd04&feature=email
Exercise: Quick Energy
1.
2.
Muscles only contain enough ATP for a
few seconds of intense activity
Then, muscle cells produce their ATP
by lactic acid fermentation.
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Lasts only about 90 seconds or about 200 300 meters.
Produces lactic acid, which requires oxygen
debt (must repay after the race with plenty
of heavy breathing).
Exercise: Long-Term Energy
(Longer than 90 seconds)
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Cellular Respiration is the only
way to generate a continuing
supply of ATP
Releases energy slowly (why
athletes must pace themselves)
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Body stores energy in muscle and
other tissues in the form of the
carbohydrate glycogen (usually
enough to last for 15 - 20 min.)
After that, your body begins to break
down other stored molecules,
including fats, for energy
Photosynthesis vs. Respiration
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Photosynthesis and cellular respiration take
place in opposite directions!
Photosynthesis: Use light energy to build a sugar.
carbon dioxide + water + light energy → sugars + oxygen
Respiration: Break down sugar to release energy.
oxygen + sugars → carbon dioxide + water + energy
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Respiration: Break Down Glucose
Photosynthesis: Build Glucose
Photosynthesis vs. Respiration
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Cellular Respiration
Occurs In:
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All eukaryotes
Some prokaryotes
Photosynthesis
Occurs In:
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Plants
Algae
Some bacteria
F. Review
1. What is the source of carbon for cellular respiration?
Glucose (C6H12O6) is the carbon source.
Review
2. Where do Stages 2 and 3 of cellular respiration take place?
in mitochondria