Cellular Respiration and Fermentation

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Chapter 9

• Cellular Respiration and Fermentation

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Chemical energy and food

• How much energy is in food?
• When 1 gram of glucose (C6H12O6) is burned in the
  presence of oxygen, 3811 calories are released.
• What is a calorie? A calorie is the amount of
  energy needed to raise the temperature of 1 gram
  of water 1 degree Celsius.

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Chemical energy and food

• On a food label Calories (with a capital C)
  represent kilocalories. 1 kilocalorie 1000
  calories.
• Cells use the energy in glucose by slowly
  releasing it.

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Chemical energy and food

• How many calories are in 2 crackers?
• How many calories are in 6 crackers?

60,000
180,000
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• This SLOW release of energy from glucose is
  called CELLULAR RESPIRATION

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• We think of respiration as breathing
• think of breathing as gas exchange (O2 in and CO2
  out) to help you do cellular respiration
• gas exchange occurs at the cellular level to
  drive cellular respiration
• O2 is a reactant of cellular respiration
• CO2 is a waste product of cellular respiration
• Breathing is just the way you get these gases
  into and out of your body.

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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.
• Oxygen glucose ? carbon dioxide water
  energy
• O2 C6H12O6 ? CO2 H2O ATP

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Overview of Cellular Respiration

• What is the balanced chemical equation for
  cellular respiration?
• 6O2 C6H12O6 ? 6CO2 6H2O 36 ATP

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• Energy released can be in the presence of oxygen
  or not. When oxygen is present, more energy can
  be released.
• The process always begins with Glycolysis, and
  will be followed by another process depending on
  whether or not oxygen is present.

Glycolysis
O2
no O2
Fermentation
Krebs Cycle
Electron Transport Chain
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• Mitochondria - Energy
• Inner membrane is highly folded to increase
  surface area

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Glycolysis (part 1)

• Glycolysis is the process in which one molecule
  of glucose (C6H12O6) is broken in half, producing
  two 3 carbon molecules of pyruvic acid (called
  pyruvate).
• Uses 2 ATP molecules but 4 ATP molecules are
  created. Net gain 2 ATP

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Glycolysis

• Glycolysis uses an electron carrier called
  similar to NADP called NAD.
• Similarly, the way it carries electrons is
• NAD 2 electrons H ? NADH
• Glycolysis occurs in the cytoplasm.

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Fermentation (part 2 option 1)

• Fermentation also occurs in the cytoplasm.
• Fermentation is the process by which cells
  release from food molecules in the absence of
  oxygen (anaerobic).
• After glycolysis, if there is no oxygen,
  fermentation may occur. Fermentation itself does
  not produce ATP, but it regenerates NAD to
  propel more glycolysis which does create ATP.

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There are two types of fermentation

• a. Alcoholic fermentation used by yeast. It
  produces alcohol as waste. It uses pyruvic acid
  produced in glycolysis.
• pyruvic acid NADH ? alcohol CO2 NAD

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• We can use this to help us make things such as
  bread and wine

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There are two types of fermentation

• b. Lactic acid fermentation occurs in cells
  other than yeast. Process produces lactic
  acid.
• pyruvic acid NADH ? lactic acid NAD

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• During rigorous exercise, your body gets behind
  in getting oxygen to your muscle cells.
• Your muscles switch from aerobic respiration
  (using oxygen) to anaerobic fermentation (does
  not use oxygen).
• Lactic acid can build up in your muscles- you
  feel a painful, burning sensation and may feel
  sore.

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• Lactic acid is also used by bacteria that are
  used to produce yogurt and other foods.
• Also used to make sourdough breads, sauerkraut,
  pickles and olives

?yogurt Sauerkraut ?
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Aerobic Cellular Respiration(part 2 option 2)

• The remaining 90 of the energy from the glucose
  molecule that was not used in glycolysis is used
  in the part of cellular respiration that requires
  oxygen (aerobic).

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The Krebs Cycle

• breaks down pyruvic acid from glycolysis into
  carbon dioxide (CO2) releasing energy as ATP,
  NADH, and FADH2.
• ATP stores energy in its phosphate bonds
• NADH and FADH2 store energy from high-energy
  electrons.

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In the Electron Transport Chain,

• the energy from electrons that is stored in NADH
  and FADH2 is transferred between electron carrier
  molecules and is used to make ATP.
• Used O2, NADH, FADH2
• Produced ATP, H2O

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• The Krebs Cycle and Electron Transport Chain
  occur in the mitochondria.

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The Totals

• Cellular respiration produces 36 ATP molecules.
• More ATP is produced with oxygen than without.
  Cellular respiration is more efficient using
  oxygen.

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Energy and Exercise Quick Energy

• Running a short race, you use ATP in your
  muscles, and produce new ATP by lactic acid
  fermentation and cellular respiration.
• When sprinting, you produce most of your ATP
  using lactic acid fermentation because you have
  run out of oxygen for the Krebs cycle.
• You breathe heavily after you finish a race to
  rebuild your ATP supply.

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Energy and Exercise Long-term Energy

• When running a long race, you use carbohydrate
  energy stored as glycogen from your muscles and
  other tissues. This will give you enough energy
  for up to 20 minutes of activity.
• After using up glycogen, your body will use up
  fats for energy.
• Aerobic exercises like running and swimming are
  beneficial for weight control.

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Comparing Photosynthesis and Cellular Respiration

• If storing energy is compared to money in a
  savings account, photosynthesis deposits the
  energy and cellular respiration withdraws the
  money.
• Cellular Respiration is the reverse reaction of
  photosynthesis.

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• What is the formula for photosynthesis?
• 6CO2 6H2O light ? 6O2 C6H12O6
• What is the formula for cellular respiration
  (think about the opposite)?
• 6O2 C6H12O6 ? 6CO2 6H2O ATP

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• Photosynthesis uses CO2 in the atmosphere, but
  cellular respiration puts it back
• Photosynthesis releases O2 into the atmosphere
  but cellular respiration using O2 to release
  energy from the food
• Cellular respiration occurs in all eukaryotes and
  some prokaryotes
• Photosynthesis occurs only in plants, algae, and
  some bacteria. Other organisms (heterotrophs) get
  their food by consuming other organisms.