Cellular Energetics

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Cellular Energetics

• Energy is transferred from organism to organism
  in a process that begins with photosynthesis and
  ends with cellular respiration

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Unit 5 Key learnings

• Autotrophs "produce" the energy that they use,
  while heterotrophs must "consume" their energy
  sources.
• Although some reactions result in a net storage
  of energy, others result in a net release.
• Biochemical pathways are influenced by enzymes.

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Unit 5 Essential question

• How do the processes of photosynthesis and
  cellular respiration show evidence of chemical
  reactions?

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Launch activity Priestley's bell jar experiment
Here are three key observations that need to be
accounted for

• Plants placed into a sealed bell jar survive
• Mice placed into a sealed bell jar die
• Mice placed into a sealed bell jar with plants
  survive

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Question Why do mice placed into a sealed bell
jar only survive when they are accompanied by
plants?

• Animals depend on the oxygen produced by plants
  (photosynthesis) to survive
• While plants require carbon dioxide to survive,
  they are constantly releasing it as a waste
  product from their own cellular respiration.

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Unit 5 Concepts

• Autotrophs versus heterotrophs (C)
• Chemical reactions (E)
• Structural and functional similarities between
  chloroplasts and mitochondria (E)
• Photosynthesis (I)
• Cellular respiration (I)

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Essential question 1

• How do the abilities of an autotroph differ from
  those of a heterotroph?

10/18/2009
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I. Energy flows between organisms in living
systems.

• Almost all of the biochemical energy on Earth
  comes directly or indirectly from the sun.
• Plants, algae, and some bacteria absorb energy
  from the sun and convert it into chemical energy
  stored in organic compounds (Photosynthesis).
• ALL organisms break down the organic compounds
  and release the energy (Cellular Respiration).

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Energy Flow through an ecosystem
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I./2. Some organisms are producers and others are
consumers.

• Autotrophs are organisms that use sunlight
  (Photosynthesis) or inorganic compounds
  (Chemosynthesis) to make energy containing
  organic compounds, then break them down for use
  in their cells (Cellular Respiration).
• Heterotrophs are organisms that consume organic
  compounds in their food and break them down for
  energy (Cellular Respiration).

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Phytoplankton production in the Arabian sea
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Question True/False Plants conduct only
photosynthesis, and animals conduct only cellular
respiration.

• False Animals conduct only cellular respiration
  (the release of energy), but Plants conduct both
  (storage and release).

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Unit 5 Concepts

• Autotrophs versus heterotrophs (C)
• Chemical reactions (E)
• Structural and functional similarities between
  chloroplasts and mitochondria (E)
• Photosynthesis (I)
• Cellular respiration (I)

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Essential question 2
How do intermediates aid in coupled reactions?
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I. Cellular respiration is a stable release of
energy.

• Burning matter releases energy very quickly as
  heat and light (very unstable release).
• Cellular respiration is a series of controlled
  reactions that occurs slowly, releasing a little
  energy at a time, re-storing it again and
  eventually producing useable ATP molecules.

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Question What would happen to a human if energy
was not released in a controlled way?
All scientific data suggests that there is
nothing spontaneous about human combustion!
Theres always a clue.
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II. Energy is released from ATP (decomposition)
in order to power a cells chemical reactions.
ATP ADP P a little bit of
energy
Adenosine TRIphosphate (ATP) Adenosine
DIphosphate (ADP)
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III. Several different molecular systems function
like the ATP-ADP system.

• NADPH NADP H
• NADH NAD H
• FADH2 FAD H2

Energy carriers (intermediates)
Energy acceptor
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Unit 5 Concepts

• Autotrophs versus heterotrophs (C)
• Chemical reactions (E)
• Structural and functional similarities between
  chloroplasts and mitochondria (E)
• Photosynthesis (I)
• Cellular respiration (I)

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Essential question 3
How are the structures of chloroplasts and
mitochondria related?
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Compare and contrast

• Mini lesson- take some notes!
• Collaborative compare and contrast
• Group sharing of graphic organizers

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I. Both mitochondria and Chloroplasts use proton
pumps to build concentration gradients.

• Proton pumps actively transport hydrogen protons
  (H).
• Each time an electron passes through the pump,
  one proton is transported.
• These pumps are active so, they are able to
  create powerful concentration gradients on one
  side of the membrane.

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II. Both mitochondria and chloroplasts use ATP
synthase enzymes to convert proton (H)
concentration gradients into ATP bond energy.

• When a proton (H) concentration gradient exists,
  this represents the ability to do work.
• Protons passing through an ATP synthase
  channel (down their gradient) will cause a
  Phosphate to be added to ADP (di-phosphate),
  converting it into ATP (tri-phosphate) and
  storing energy.

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III. The thylakoids contained within a
chloroplasts outer membrane create a membrane to
pump across.
two outer membranes
thylakoid compartment
thylakoid membrane system inside stroma
stroma
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The light reactions of a chloroplast
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IV. Mitochondria contain a folded inner membrane
within the outer membrane, creating an inner
space and an outer space to pump between.
inner mitochondrial membrane
outer mitochondrial membrane
inner compartment
outer compartment
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The Mitochondrial Electron Transport Chain
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Along with your partner, and using the graphic
organizer provided

• Tell me how the structure of chloroplasts and
  mitochondria are related (and why)
• Identify several ways the structures are
  different (in regards to)
• Using the headings provided (in regards to),
  explain how the structures are different
• Share your pairs work with another pair!

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Unit 5 Concepts

• Autotrophs versus heterotrophs (C)
• Chemical reactions (E)
• Structural and functional similarities between
  chloroplasts and mitochondria (E)
• Photosynthesis (I)
• Cellular respiration (I)

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Essential questions 4-5
4. Why is the process of photosynthesis
considered to be a synthesis reaction? 5. How
does energy flow from process to process during
photosynthesis?
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I. Photosynthesis is the production of
carbohydrates from CO2 and H2O, with the help of
sunlight.
1.
sunlight
6CO2 6H2O --------------gt C6H12O6 6O2
carbon dioxide
Glucose
water
oxygen
Light energy in
Chemical energy out (sugar)
Waste gas
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Question Why is photosynthesis called a
synthesis reaction?

• Two small molecules are put together to form a
  larger one
• The energy state of the product (sugar) is
  greater than the energy state of the reactants
  (water and carbon dioxide)

Synthesis
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II. Photosynthesis happens in 3 parts

• Photolysis (Light dependent)
• Electron Transport chain (Light dependent)
• Calvin cycle (Light independent)

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Chloroplast structure
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Excitation of electrons in Chlorophyll
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The Electron Transport Chains of Photosystems I
and II
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Photolysis of Water
Oxygen production
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The Light dependent reactions
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III. Electrons in 2 photosystems are excited and
replaced.

• Clusters of pigments are embedded in the bilayers
  of the thylakoids (Photosystems I and II).
• Energy from the sun causes electrons in the
  pigments to jump to a higher energy level and
  become excited (First Photosystem I, then
  Photosystem II).

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III./3. The excited electrons move into 2
electron transport chains (ETC).

• H2O is split by an enzyme located near the
  pigments of Photosystem II in the interior of the
  thylakoid (photolysis).
• The electrons come from the hydrogen, which are
  now released as free protons (H).
• The Oxygen from two water molecules fuse to form
  O2 gas, which is released as waste into the air.
• Photosystems IIs missing electrons are replaced
  by electrons from split water molecules
  (Photolysis).
• Photosystem Is electrons are replaced by those
  of Photosystem II.

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IV. Two electron transport chains in the
thylakoid membrane produce energy storage
compounds- ATP and NADPH.

• Excited electrons from Photosystem I travel
  through an ETC and help produce NADPH.
• The energy from the electrons is stored in the
  form of NADPH as an H is added to NADP.
• These electron will be replaced by electrons from
  Photosystem II.

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IV./2. Excited electrons from photosystem II move
to replace the ones lost from photosystem I.

• Along the way, PS IIs electrons pass through a
  pump that pulls in H.
• A concentration gradient of H is created inside
  the thylakoid.
• H floods back out through an enzyme channel
  called ATP synthase.
• Each H that is transported catalyzes the
  production of one ATP molecule.

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IV./3. NADPH and ATP now hold chemical energy
that can be used later (converted from light
energy.

• The energy in these compounds will be used in the
  Calvin cycle to build sugars (coupled reactions).
• The energy will be released by converting them
  back into their original forms ADP and NADP
• ADP and NADP will be returned to allow the light
  reactions to occur again- these are the necessary
  reactants for those reactions.

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Question Is there a net gain or loss of energy
after the light reactions?

• Gain The organism did not need to use its own
  energy to from ATP and NADPH
• It got this energy from the Sun!

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Summary With your partner, answer the following
questions

• What molecule donates electrons to keep the
  electron transport process going?
• Where are the electrons from PS I going?
• What two molecules carry energy out of the light
  dependent reactions?

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V. NADPH and ATP from the light reactions enter
the Calvin Cycle for Carbon Fixation.

• These are the Light independent reactions since
  they don't require light.
• Carbon Fixation is the transfer of atmospheric
  carbon into energy containing organic compounds.
• The Calvin cycle is the most common type of
  fixation.

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Stomata allowing gas into a plant
Question Why might plants want to regulate the
opening of their stomata? To prevent water loss
in dry climates
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The Calvin Cycle
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VI. The Calvin cycle is a series of
enzyme-assisted chemical reactions that produces
ONE glucose sugar molecule.

• 6 carbon dioxide molecules are added to 6
  five-carbon compounds forming 6 six-carbon
  molecules.
• Each resulting six-carbon compound immediately
  splits into 2 three-carbon compounds (a total of
  12 are formed).
• Phosphate groups from ATP and electrons from
  NADPH are added to the 12 three-carbon compounds
  forming 12 three-carbon sugars.

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VI. Continued

• Two of the resulting three-carbon sugars are used
  to produce glucose.
• The other 10 three-carbon sugars are used to
  regenerate the initial five-carbon compounds (ATP
  is required).
• In the end, 6 carbon dioxide molecules enter the
  cycle to make one six-carbon glucose.
• The energy required to do this came from the
  NADPH and ATP that was formed with the help of
  the suns energy.

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Question? Why is this a cycle?
We finish where we started?
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VII. Three factors determine the rate of
photosynthesis.

• Each of these factors will increase the rate of
  photosynthesis until a saturation point is
  reached.
• Amount of Sunlight
• Amount of Carbon Dioxide
• Temperature
• Increasing these factors above the saturation
  point will not increase sugar production.

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sunlight
Question Which molecules link the Light
Reactions to the Dark Reactions?
Light- Dependent Reactions
12H2O
6O2
ATP
NADP
ADP Pi
NADPH
6CO2
Calvin-Benson cycle
6 RuBP
12 PGAL
Light- Independent Reactions
6H2O
phosphorylated glucose
end products (e.g., sucrose, starch, cellulose)
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The ins and outs of photosynthesis
In what part of the process are each of these
molecules important?
6CO2 6H2O --------------gt C6H12O6 6O2
Calvin Cycle
Photolysis
Photolysis
Calvin Cycle
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A summary of Photosynthesis
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Essential question 6
How can photosynthetic pigments be separated
using paper chromatography? Lab time!
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I. Pigments like Chlorophyll allow an autotroph
to use sunlight as the energy source in these
reactions.

• An object is the color you see because it
  reflects that color light.
• Chlorophyll A and B are green pigments (reflect
  green and yellow light).
• Carotenoids give their color to many vegetables
  and flowers and produce the fall color change you
  see.
• The combination of many pigments allows an
  autotroph to gather much more light.

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II. Overlapping pigments allow photosynthesizers
to maximize the amount of solar energy they
gather.
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Unit 5 Concepts

• Autotrophs versus heterotrophs (C)
• Chemical reactions (E)
• Structural and functional similarities between
  chloroplasts and mitochondria (E)
• Photosynthesis (I)
• Cellular respiration (I)

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Essential questions 7-8
7. Why is cellular respiration considered to be
decomposition reaction? 8. How does energy flow
through the process of cellular respiration?
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Pulmonary and cellular respiration
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I. Cellular respiration converts the energy
contained in organic compounds into a usable form
(ATP).
enzymes C6H12O6 6O2
--------------gt 6CO2 6H2O energy Glucose
gas gas water
ATP
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Question Why is Cellular respiration called a
decomposition reaction?

• One large molecules is taken apart to form two
  smaller ones
• The energy state of the reactant (sugar) is
  greater than the energy state of the products
  (water and carbon dioxide)

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II. Carbohydrates, Lipids and Proteins can all be
used for Cellular respiration.

• Proteins and Nucleic Acids are used last, since
  they are important structural and information
  storage molecules.
• 1 gram of lipids stores more energy than 2 grams
  of carbohydrates
• Carbohydrates are the easiest to use.

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Sources of energy
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Energy may flow in one of several paths during
cellular respiration.
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III. Glycolysis is the breakdown of glucose into
Pyruvate and ATP. This process always begins the
process of carbohydrate metabolism.

• Glycolysis occurs in the cytoplasm, not the
  mitochondria.
• A six-carbon molecule (glucose) is broken down
  into a three-carbon molecule called pyruvate.
• 2 Molecules of ATP are used for Glycolysis, but 4
  are produced.
• 2 NADH molecules are formed as the molecule is
  processed (stored energy).

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An Overview of Glycolysis
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Question What is the net gain in ATP after
Glycolysis?
2 Molecules are used
4 Molecules are produced
Net Gain of 2 molecules of ATP
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IV. When oxygen is present, Aerobic respiration
converts pyruvate to many ATP molecules (34 or 36
depending on the cell).

• Aerobic respiration occurs in the mitochondria.
• If Glycolysis did not convert glucose to the
  smaller molecule pyruvate, it would be too big to
  diffuse into the mitochondria.

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Ticket in the Door

• Write down in your note packet (in complete
  sentences) the answers to the following
  questions.
• Where does glycolysis take place?
• Does glycolysis require oxygen?
• What are the reactants (inputs) and the products
  (outputs) of glycolysis?

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V. There are 3 parts to Aerobic Respiration.

• Acetyl-CoA formation
• Krebs Cycle (Citric Acid Cycle)
• The Mitochondrial Electron Transport Chain (ETC)

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1. Acetyl-CoA formation

• Pyruvate loses a Carbon as CO2.
  (3 carbon molecule 2 carbon
  molecule)
• Coenzyme A attaches to whats left and forms
  Acetyl-CoA.
• One NADH is formed.

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Acetyl CoA formation prior to the Krebs cycle
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2. Acetyl-CoA (two- carbon) enters the Krebs
cycle.

• Acetyl-CoA combines with a four-carbon molecule
  to form a six-carbon molecule.
• One CO2 exits forming a five-carbon molecule and
  producing a 2nd NADH.
• Another CO2 exits, forming a four-carbon and
  producing one ATP and a 3rd NADH.
• The four carbon compound is altered and releases
  electrons that help form FADH2.

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2. Continued

• The four-carbon compound is altered again and
  reset to its original form to re-enter the Krebs
  cycle.
• A 4th NADH is formed.
• FADH2 and the 4 NADH molecules now hold much of
  the energy previously contained in pyruvate.

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The Krebs Cycle (Citric Acid Cycle) in full
detail- you dont need to know this until
college! ?
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Basic Krebs Cycle
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3. FADH2 and NADH enter an electron transport
chain.

• Electrons from FADH2 and NADH move from molecule
  to molecule and cause H to diffuse out of the
  inner folds of the mitochondria.
• Each time an H comes back in, it catalyzes the
  production of 1 ATP (ATP synthase).
• Oxygen accepts electrons at the end of the chain,
  grabs 2 Hydrogens and forms water.

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Mitochondrial membranes
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The Mitochondrial Electron Transport Chain
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VI. If oxygen is present, aerobic respiration can
produce up to 38 molecules of ATP

• 2 (net gain) ATP from Glycolysis
• 2 (11) ATP in the Krebs cycle
• Up to 34 ATP from electron transport of all NADH
  and FADH2 created by breakdown of both pyruvate
  molecules (or 32 in some cells).

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ATP production
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Question What is the purpose of NADH and FADH2?

• Answer They carry electrons from Glycolysis and
  the Krebs Cycle to the Electron Transport Chain
  (coupling).

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Essential question 9
Why is the process of fermentation necessary in
oxygen free environments?
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Aerobic Respiration Overview
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I. In the absence of oxygen, anaerobic
respiration must take place.

• No Oxygen is present to act as the final electron
  acceptor in the electron transport chain, so
• NADH must be recycled to support Glycolysis (NADH
  H NAD).
• Fermentation allows pyruvate to act as a hydrogen
  acceptor.

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II. Lactic Acid Fermentation occurs in Animals.

• The build up of Lactate causes muscle soreness.
• When completed in bacteria, yogurt can be
  produced.
• When used by fungi, cheese may be produced.

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III. Alcoholic fermentation occurs in Yeasts.

• A type of fungi called Yeast is responsible for
  many of our alcoholic beverages, as well as our
  breads.
• CO2 bubbles off and allows bread to rise, or beer
  to become carbonated.
• Ethanol kills yeast when present in high levels,
  so there is a limit to the strength of this type
  of beverage (12).

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Fermentation Cycles
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Question If bread dough rises because of
alcoholic fermentation, why doesnt eating bread
make you become intoxicated?

• Answer Because baking the bread causes the
  evaporation of the small amount of alcohol that
  was produced.

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IV. Aerobic respiration allows Glucose to be used
more efficiently.

• Glycolysis Aerobic respiration yields between
  36 and 38 ATP (dependant on the type of cell).
• Glycolysis Fermentation yields 2 ATP
  (Glycolysis produces the only ATP)

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Aerobic and Anaerobic Comparison
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V. Exercise may be aerobic or anaerobic.

• Jogging and walking are aerobic.
• Sprint activities and weight training are
  anaerobic.

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V./1. Exercise that occurs at a pace that allows
you to work without heavy breathing is Aerobic.

• There is plenty of oxygen to act as the final
  electron acceptor.
• A body will release energy efficiently, and can
  maintain this level for quite some time.

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V./2. Exercise that causes you to breath heavily
is anaerobic.

• Your cells run out of oxygen to use as an
  electron acceptor, and you begin to recycle NADH.
• Glycolysis provides your only source of ATP.
• Lactate builds up in your muscles and causes
  soreness.

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Question Why do you get so tired during and
after Anaerobic exercise?

• Answer Your body is using energy inefficiently,
  and you quickly run out of energy to burn.

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The ins and outs of cellular respiration
In what part of the process are each of these
molecules important?
enzymes C6H12O6 6O2
--------------gt 6CO2 6H2O energy
Glycolysis
ETC
Krebs Cycle
ETC
ETC
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A summary of Cellular Respiration