Cellular Respiration and Fermentation

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Cellular Respiration and Fermentation
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Cellular Respiration

• Complex process (biochemical pathway) in which
  cells make ATP by breaking down organic compounds
• Heterotrophs take in food, break it into glucose
• Autotrophs make glucose, break it down

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Cellular Respiration

• Two phases
• Glycolysis
• Yields small amounts of ATP
• Other products lead to fermentation
• Fermentation (anaerobic)
• Lactic acid fermentation
• Alcoholic fermentation

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Glycolysis

• Two main pathways
• Aerobic oxygen present
• Produces greater amounts of ATP
• AKA oxidative respiration
• Anaerobic oxygen absent
• Products may enter fermentation to make
  additional ATP

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Glycolysis

• Step 1
• Two phosphate molecules from ATP attach to
  glucose
• ATP -gt ADP
• Glycolysis

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Glycolysis

• Step 2
• Six carbon compound is split into two 3-C
  compounds (PGAL or G3P)
• Glycolysis

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Glycolysis

• Step 3
• Two PGAL/G3P molecules are oxidized (LEO says
  GER)
• Produces two new 3-C molecules
• Accompanied by the reduction of NAD to NADH
  (similar to NADPH)
• Glycolysis

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Glycolysis

• Step 4
• Phosphate groups added in steps 1 3 are removed
  from the 3-C compound
• Produces two molecules of pyruvic acid
• Each phosphate is added to ADP to produce ATP (4
  molecules)
• Glycolysis

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Glycolysis Overview
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Glycolysis Spreadsheet

• Two ATP are used to start glycolysis
• Four ATP are produced
• Net gain 2ATP
• Equates to 2 efficiency

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Fermentation

• In the absence of oxygen cells can convert
  pyruvic acid into other compounds
• Fermentation
• Does not produce additional ATP
• Regenerates NAD to keep glycolysis going

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Lactic Acid Fermentation

• An enzyme converts pyruvic acid into another 3-C
  compound called lactic acid
• The miracle of fermentation
• Involves the transfer of 2 H from NADH to
  pyruvic acid
• NADH is oxidized
• NAD is used in glycolysis

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Lactic Acid Fermentation

• Lactic acid fermentation is done by some fungi,
  some bacteria like the Lactobacillus acidophilus.
  in yogurt, and sometimes by our muscles

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Lactic Acid Fermentation

• Normally our muscles do cellular respiration
  using O2 supplied by our lungs and blood
• When the oxygen supplied by the lungs and blood
  system cant get there fast enough to keep up
  with the muscles needs, our muscles can switch
  over and do lactic acid fermentation

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Lactic Acid Fermentation

• It is the presence of lactic acid in yogurt that
  gives it its sour taste, and it is the presence
  of lactic acid in our muscles the morning after
  that makes them so sore

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Lactic Acid feel the burn

• Gradually washed away by the blood stream and
  carried to the liver (which is able to get rid of
  it)
• Our over-exerted muscles feel stiff and sore even
  if they havent been physically injured.

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Alcoholic Fermentation

• Used by some plants, bacteria, and yeast, a
  single-celled fungi
• Converts pyruvic acid into ethyl alcohol

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Alcoholic Fermentation

• Step one
• CO2 is removed from pyruvic acid
• Leaving a 2-C compound
• Step two
• H are added to the 2-C compound to form ethyl
  alcohol
• H come from NADH

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Alcoholic Fermentation
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Alcoholic Fermentation

• Basic concept of beer and wine industry
• CO2 is a by product for wine and allowed to
  escape
• In beer, carbon dioxide creates the carbonation

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Alcoholic Fermentation

• Bread relies on the same process
• Yeast produce CO2
• Bread rises
• Alcohol is cooked off

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Energy Yield

• Kilocalorie
• 1 kcal 1,000 calories (c)

Energy yield of fermentation is 2 ATP molecules
with 7.3 Kcal of energy for a total energy yield
of 14.6 Kcal Complete glucose breakdown gives
an energy yield of 686 Kcal. Energy yield from
glycolysis is only 2.1 of that from complete
glucose breakdown
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Energy Yield

• Anaerobic pathways are not very energy efficient
• Evolved in bacteria who obtained all energy by
  glycolysis
• Works for unicellular organisms
• Aerobic respiration evolved when photosynthesis
  first occurred

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Aerobic (Oxidative) Respiration

• If oxygen is available
• Two major stages
• Krebs cycle
• Electron transport chain

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Prokaryotes

• Carry out cellular respiration in the cytosol of
  the cell
• No membrane bound organelles

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Eukaryotes

• Carry out respiration in the mitochondrial matrix
• Space inside inner membrane of the mitochondria

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Mitochondrial Matrix

• Contains enzymes needed to catalyze the reactions
  of the Krebs cycle
• Acetyl coenzyme A
• AKA Acetyl CoA
• Pyruvic acid CoA -gt Acetyl CoA CO2

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Krebs cycle (a.k.a the Citric Acid Cycle)

• Biochemical pathway
• Breaks down acetyl CoA
• Producing CO2, H , ATP
• 5 main steps

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Step 1

• Krebstca
• 2-C molecule acetyl CoA combines with a 4-C
  oxaloacetic acid to produce 6-C citric acid
• Why Krebs cycle is AKA citric acid cycle

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Step 2

• Krebstca
• Citric acid releases CO2 and a H to form a 5-C
  compound
• By losing a H citric acid is oxidized
• Leo says Ger
• H is transferred to NAD -gt NADH
• NADH is reduced

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Step 3

• Krebstca
• 5 C compound also releases CO2 and H
• H is added to NAD making NADH
• A molecule of ATP is synthesized from ADP

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Step 4

• Krebstca
• 4-C compound releases a H
• H is used to reduce FAD to FADH2
• (flavin adenine dinucleotide) an electron
  acceptor- takes electrons

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Step 5

• Krebstca
• 4-C compound releases H to regenerate
  oxaloacetic acid to keep cycle going
• H reduces NAD to NADH

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Net Result

• In glycolysis, one glucose molecule produces 2
  pyruvic acid, which form 2 molecules of acetyl
  CoA
• One glucose causes two turns of the Krebs cycle
• Produces 8 NADH, 2 FADH2, 2 ATP, 6 CO2

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Krebs Cycle
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Krebs Cycle (simple)
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Electron Transport Chain

• ATP is produced when NADH and FADH2 release H
• Regenerates NAD and FAD

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Electron transport chain
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Electron transport chain
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Electron Transport Chain

• krebstca

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Electron Transport Chain

• Electrons in H from NADH and FADH2 are at high
  energy
• H are passed along a series of molecules
• As they move, the electrons lose energy
• Energy lost is used to pump protons from one side
  of the mitochondrial matrix
• Creates a concentration gradient

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Chemiosmosis

• Concentration gradient of H drives the synthesis
  of ATP by chemiosmosis
• Same process that generates ATP in photosynthesis

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Role of Oxygen

• Oxygen serves as the final electron acceptor in
  aerobic respiration
• Accepts the protons that were once part of the
  hydrogen atoms supplied by NADH FADH2
• O2 4 e- 4H -gt 2H2O
• Water is formed

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Energy Yield

• Glycolysis produces 2 ATP
• Krebs cycle produces 2 ATP
• NADH generates 3 ATP
• FADH2 generates 2 ATP

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Energy Yield
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Energy Yield

• Actual number varies
• Most eukaryotes produce 36 ATP per molecule of
  glucose aerobically/ 2 by anaerobic respiration
• 66 efficient when a cell produces 38 ATP

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Overview of Cellular Respiration

• respiration