Chapter 9 Cellular Respiration: Harvesting Chemical Energy

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Chapter 9 Cellular Respiration Harvesting
Chemical Energy
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Is this a process of turning food into energy?
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Rs - Equation

• C6H12O6 6 O2 6 CO2 6 H2O
  and energy
• The energy is released from the chemical bonds in
  the complex organic molecules.

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Respiration - Preview

• The process of releasing Energy from food.
• Food - Stored Energy in chemical
  bonds.
• ATP - Useable Energy for cell work.

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Focus of Chapter

• 1. Purpose - what is the reaction suppose
  to do?
• 2. Location - where is it at?
• 3. Requirements - what is needed to make it
  run?
• 4. Products - what does it produce?

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Oxidation - definitions

• Loss of electrons.
• Loss of energy.
• Loss of Hydrogens from Carbons.

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Reduction - definitions

• Gain of electrons.
• Gain of energy.
• Gain of Hydrogens to Carbons.
• Comment - be careful not to use reduction in
  lay terms.

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Redox reactions
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Redox reactions

• Reactions are usually paired or linked together.
• Look for these links as we study Rs.
• Many of the reactions will be done by
  phosphorylation

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Phosphorylation

• Adding a phosphate group to a molecule.
• The phosphate group adds energy to the molecule
  for chemical reactions.

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Phosphorylation
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Cell Respiration - parts

• 1. Glycolysis
• 2. Krebs Cycle
• 3. Electron Transport Chain

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Glycolysis

• Glyco- glucose.
• -lysis to split
• Universal step in all Rs types.
• Likely to earliest type of cell energy processes.

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Glycolysis

• Function - To split glucose and produce NADH and
  ATP.
• Location - Cytoplasm.

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Electron Carrier Compounds

• Molecules that transport or shuttle electrons
  within the cell.
• Exist it two forms
• Oxidized (ox)
• Reduced (red)

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NAD

• Nicotinamide Adenine Dinucleotide
• NAD 2 e- NADH
• NAD oxidized form
• NADH reduced form

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Glycolysis -Requirements

• Glucose
• 2 ATP
• 4 ADP
• 2 NAD

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Glycolysis - Products

• 2 Pyruvic Acids (a 3C acid)
• 2 ADP
• 4 ATP
• 2 NADH

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Net Result

• 2 ATP per glucose
• 2 NADH

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Energy Investment Phase
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Energy Harvest Phase
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Krebs Cycle

• Also called
• Citric Acid Cycle
• Tricarboxylic Acid Cycle

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Krebs Cycle

• Function Oxidize pyruvic acid to CO2
• Produce NADH and FADH2
• Location Mitochondria matrix

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Formation of Acetyl CoA
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Krebs Cycle -Requirements

• Pyruvic acid (3C acid)
• Coenzyme A
• 4 NAD
• 1 ADP
• 1 FAD
• Double this list for each glucose.

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Krebs Cycle - Products

• 3 CO2
• Acetyl CoA
• 4 NADH
• 1 ATP
• 1 FADH2
• Double this list for each glucose.

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Krebs Cycle

• Produces most of the cell's energy in the form of
  NADH and FADH2
• Does NOT require O2

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Comment

• The ATPs produced directly in Krebs Cycle and in
  Glycolysis are by
• Substrate-level phosphorylation
• The Pi group is transferred from a substrate to
  ADP.

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Electron Transport Chain

• ETC or Electron Transport System (ETS).
• A collection of proteins that are structurally
  linked into units.

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ETC

• Uses sets of Cytochromes, Fe containing proteins
  to pass electrons.
• The Cytochromes alternate between RED and OX
  forms and pass electrons down to O2

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ETC

• Function Convert NADH and FADH2 into ATP.
• Location Mitochondria cristae.

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ETC - Requirements

• NADH or FADH2
• ADP
• O2

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ETC - Products

• NAD and FAD
• ATP
• H2O

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ETC - ATP Yields

• Each NADH -- 3 ATP
• Each FADH2 -- 2 ATP

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Chemiosmotic Hypothesis

• ETC energy is used to move H (protons) across
  the cristae membrane.
• ATP is generated as the H diffuse back into the
  matrix.

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ATP Synthase

• Uses the flow of H to make ATP.
• Works like an ion pump in reverse, or like a
  waterwheel under the flow of H water.
• Oxidative phosphorlaytion

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Alcoholic Fermentation

• Done by yeast, a kind of fungus.

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Alcoholic Fermentation

• Uses only Glycolysis.
• An incomplete oxidation - energy is still left in
  the products (alcohol).
• Does NOT require O2
• Produces ATP when O2 is not available.

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Lactic Acid Fermentation

• Uses only Glycolysis.
• An incomplete oxidation - energy is still left in
  the products (lactic acid).
• Does NOT require O2
• Produces ATP when O2 is not available.

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Lactic Acid Fermentation

• Done by human muscle cells under oxygen debt.
• Lactic Acid is a toxin and causes soreness and
  stiffness in muscles.

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Fermentation - Summary

• Way of using up NADH so Glycolysis can still run.
• Provides ATP to a cell even when O2 is absent.

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Aerobic vs Anaerobic

• Aerobic - Rs with O2
• Anaerobic - Rs without O2
• Aerobic - All three Rs steps.
• Anaerobic - Glycolysis only.

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Strict vs. Facultative

• Strict - can only do Rs this one way.
• Facultative - can switch Rs types depending on O2
  availability. Ex - yeast

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Question

• Since yeast can do both aerobic and anaerobic Rs,
  which is the better process if given a choice?
• Check the ATP yields from both processes.

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ATP yields by Rs type

• Anaerobic - Glycolysis only Gets 2 ATPs per
  glucose.
• Aerobic - Glycolysis, Krebs, and ETC. Generates
  many more ATPs per glucose.

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Aerobic ATP yield

• Glycolysis - 2 ATPS, 2 NADHs
• Krebs - 2 ATPS, 8 NADHs, 2 FADH2
• Each NADH 3 ATP
• Each FADH2 2 ATP

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ATP Sum

• 10 NADH x 3 30 ATPs
• 2 FADH2 x 2 4 ATPs
• 2 ATPs (Gly) 2 ATPs
• 2 ATPs (Krebs) 2 ATPs
• Max 38 ATPs per glucose

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However...

• Some energy is used in shuttling the NADH from
  Glycolysis into the mitochondria.
• Actual ATP yield 36/glucose

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Yeast

• Would rather do aerobic Rs it has 18x more
  energy per glucose.
• But, anaerobic will keep you alive if oxygen is
  not present.

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Importance of Rs

• Convert food to ATP.
• Provides materials for use in other cellular
  pathways.

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Other Importances of Respiration

• Alcohol Industry - almost every society has a
  fermented beverage.
• Baking Industry - many breads use yeast to
  provide bubbles to raise the dough.

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Question

• Why is the alcohol content of wine always around
  12-14?
• Alcohol is toxic and kills the yeast at high
  concentrations.

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Swiss Cheese

• Holes are bubbles of CO2 from fermentation.

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Summary

• Know the 3 main reactions of Rs and the 4
  required items for each.
• Appreciate the importances of Rs.

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Rs - Equation

• C6H12O6 6 O2 6 CO2 6 H2O
  and energy
• Which part of the equations represent which of
  the 3 Rs reactions?