Cellular Respiration

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Cellular Respiration
2
Cellular Respiration

• Cellular respiration releases chemical energy
  from sugars and other carbon-based molecules to
  make ATP.
• It is an aerobic process.
• needs oxygen to take place.

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Cellular Respiration

• Cell respiration takes place in the mitochondria.
• Foods are broken down into small molecules like
  glucose.
• Glucose is broken down during glycolysis.

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Glycolysis

• Glycolysis
• Takes place BEFORE cell respiration.
• Splits the glucose molecule into two three-carbon
  molecules and makes two molecules of ATP.
• It takes place in the cytoplasm of the cell.
• It is an anaerobic process.
• Does NOT require oxygen to take place.

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Glycolysis

• 1. Two ATP molecules are used to energize a
  glucose molecule.
• The glucose is then split into two three-carbon
  molecules.
• 2. Energized electrons from the three-carbon
  molecules are transferred to molecules of NAD.
• This makes NADH. (this is an enzyme that helps
  energy production)
• A series of reactions convert the three-carbon
  molecules into pyruvate. (used in cellular
  respiration)
• 4 ATP molecules are made.

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Krebs Cycle

• The first part of cellular respiration.
• Sometimes called the citric-acid cycle.
• Produces molecules that carry energy to the
  second part of cellular respiration. (NADH and
  FADH2)
• Takes place in the interior space (matrix) of the
  mitochondria.

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Krebs Cycle

• 1. Pyruvate broken down.
• Pyruvate is split into a two-carbon molecule and
  carbon dioxide (given off as waste).
• The two-carbon molecule donates high energy
  electrons to NAD, forming a molecule of NADH.
• This will move to the electron transport chain.
• 2. Coenzyme A
• Bonds to the two-carbon molecule made by the
  breakdown of pyruvate.

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Krebs Cycle

• 3. Citric acid formed.
• The two-carbon molecule binds to a four-carbon
  molecule to form citric acid.
• Coenzyme A returns to step 2.
• 4. Citric acid broken down.
• The citric acid molecule is broken down by an
  enzyme, and a five-carbon molecule is formed.
• A molecule of NADH is made and moves out of the
  Krebs cycle.
• A molecule of carbon dioxide is given off as
  waste.

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Krebs Cycle

• 5. Five-carbon molecule broken down.
• A four-carbon molecule, a molecule of NADH, and a
  molecule of ATP are formed.
• NADH leaves the Krebs Cycle.
• Carbon dioxide is given off as waste.
• 6. Four-carbon molecule rearranged.
• Enzymes rearrange the four-carbon molecule,
  releasing high-energy electrons.
• NADH and FADH2 (another enzyme/electron carrier)
  are made.
• They leave the Krebs cycle and the four-carbon
  molecule remains.

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Krebs Cycle Products

• The Krebs cycle will break down TWO pyruvate
  molecules at the same time.
• Products
• 6 carbon dioxide molecules.
• 2 molecules of ATP
• 8 molecules of NADH
• Will go to the electron transport chain.
• 2 molecules of FADH2
• Will go to the electron transport chain.

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Electron Transport Chain

• Second part of cellular respiration.
• Energy from the Krebs cycle (NADH and FADH2) is
  transferred to a chain of proteins in the inner
  membrane of the mitochondrion.
• A large number of ATP molecules are made.
• Oxygen is used to make water molecules.
• Water and heat are given off as a waste

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Electron Transport Chain

• 1. Electrons removed.
• Proteins inside the mitochondrion take
  high-energy electrons from NADH and FADH2.
• Two molecules of NADH and one of FADH2 are used.
• 2. Hydrogen ions transported.
• Hydrogen ions are built up along the inner
  mitochondrial membrane using energy from the
  electrons.

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Electron Transport Chain

• 3. ATP produced.
• The hydrogen pumps through a protein channel in
  the mitochondrial membrane with ATP synthase.
• ATP synthase adds phosphate groups to ADP to make
  ATP molecules.
• Each pair of electrons (hydrogen) that passes
  through results in an average of 3 ATP molecules
  made.
• 4. Water formed.
• Oxygen enters the cycle and picks up extraneous
  hydrogen, forming water.
• This is given off as a waste.

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Electron Transport Chain
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Electron Transport Chain Products

• For EACH molecule of glucose the ETC can make
• Up to 34 molecules of ATP

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Cellular Respiration Products

• Up to 38 ATP are made from the breakdown of ONE
  glucose molecule.
• 2 ATP from glycolysis
• 36-34 ATP from cellular respiration (Krebs Cycle
  and Electron Transport Chain)
• Other products include carbon dioxide and water.
• The equation for cellular respiration is
• C6H12O6 6O2 6CO2 6H2O

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Fermentation

• Fermentation is an anaerobic process that takes
  place when there is less oxygen in the body (i.e.
  during strenuous activity)
• Fermentation does NOT make ATP, but it allows
  glycolysis to continue.
• Glycolysis needs NAD to pick up electrons when
  it splits glucose into pyruvate.
• Fermentation removed electrons from NADH
  molecules and recycles NAD molecules for
  glycolysis.

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Lactic Acid Fermentation in Animals

• 1. Pyruvate and NADH from glycolysis enter
  fermentation.
• Two NADH molecules are used to convert pyruvate
  into lactic acid.
• As the NADH is used, it converts back to NAD.
• 2. TWO molecules of NAD are recycled back to
  glycolysis.
• This allows your body to continue to break down
  sugar for energy!

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Alcoholic Fermentation in Plants

• 1. Pyruvate and NADH from glycolysis enter
  alcoholic fermentation.
• The NADH molecules provide energy to break
  pyruvate into alcohol and carbon dioxide.
• As the NADH are used, they are converted to NAD.
• 2. The molecules of NAD are recycled back to
  glycolysis.
• The recycling of NAD allows glycolysis to
  continue.

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Cellular Respiration and Photosynthesis

• Cellular Respiration and Photosynthesis are
  approximately the reverse of each other.
• Photosynthesis stores energy.
• Cellular Respiration releases it.