Cellular Respiration

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Cellular Respiration

• C6H12O6 6 O2? 6 CO2 6H2O 38 ATP

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Cellular Respiration An Overview

• Process by which cells convert the energy in food
  (usually glucose) into usable ATP.
• Terms to Know
• Oxidation the loss of electrons
• Compound becomes more positive
• Reduction the gain of electrons
• Compound becomes more negative
• Electrons and protons (H) travel TOGETHER
• NAD coenzyme derived from niacin acts as a H
  and e- acceptor. AN ENERGY CARRIER!

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Leo the Lion!

• LEO the lion says GER
• Loss of electrons is oxidation, gain of electrons
  is reduction

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Cellular Respiration An Overview
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Substrate-Level Phosphorylation

• An enzyme transfers a phosphate group directly
  from an organic molecule to ADP to form ATP
• The ATP produced in Glycolysis the Krebs Cycle
  is produced by this method.

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Oxidative Phosphorylation(ETC Chemiosmosis)

• The production of ATP by using energy derived
  from the redox reactions of the Electron
  Transport Chain.
• The enzyme ATP synthase is needed to
  phosphorylate the ADP to produce ATP.
• Almost 90 of the ATP produced from cellular
  respiration is produced this way.

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Cellular Respiration
Glucose
Glycolysis
ATP
Oxygen Absent
Oxygen Present
Anaerobic Respiration (Fermentation)
Aerobic Respiration (Krebs Cycle ETC)

• ATP

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Glycolysis

• glucose-splitting
• Big Picture
• Glucose (6-C) is broken down into 2 molecules of
  pyruvate (3-C)
• Occurs in the cytosol
• Occurs with or without oxygen
• Made up of 2 phases
• Energy investment phase
• Energy yielding phase

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Glycolysis Energy Investment Phase

• Glucose is converted into 2 G3P
  (Glyceraldehyde-3-phosphate)
• Requires 2 ATP

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Glycolysis Energy-Yielding Phase

• 2 G3P are converted into 2 Pyruvate (3C)
  molecules.
• Dehydrogenase enzymes remove H from intermediate
  compounds and attach them to 2 NAD to produce
  2NADH

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Net Gain in Glycolysis

• 2 ATP
• - 2 ATP (Energy investment phase)
• 4 ATP (Energy yielding phase)
• 2 ATP
• 2 NADH
• Electron carriers
• Will be used to make ATP later ?

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Choices, Choices! ?

• If oxygen is absent, anaerobic respiration occurs
• Fermentation
• Yeast some bacteria ? alcoholic fermentation
• Animal muscle? lactic acid fermentation
• If oxygen is present, aerobic respiration occurs
• Krebs Cycle and Electron Transport Chain

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Cellular Respiration
Glucose
Glycolysis
ATP
Oxygen Absent
Oxygen Present
Anaerobic Respiration (Fermentation)
Aerobic Respiration

• ATP

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Fermentation

• 2 major types
• Alcoholic and lactic acid fermentation
• NAD acts as a hydrogen acceptor during
  glycolysis
• If the supply of NAD runs out, then glycolysis
  would have to stop.
• Fermentation occurs as simply a means of
  recycling the NAD, so that glycolysis can occur
  again.

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Alcoholic Fermentation

• Occurs in some BACTERIA and YEAST
• 2 step process
• Carbon dioxide is released from pyruvate (3-C),
  forming acetaldehyde (2-C)
• Acetaldehyde is reduced by NADH (gains an
  electron), forming ethyl alcohol (ethanol)
• NAD is regenerated, thereby allowing glycolysis
  to continue
• Used to produce beer and wine

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Lactic Acid Fermentation

• Occurs in ANIMALS
• 1 step process
• Pyruvate is reduced by NADH (gains an electron),
  forming lactic acid
• NAD is regenerated, thereby allowing glycolysis
  to continue
• Occurs in muscle cells, causing muscle pain and
  fatigue

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Cellular Respiration
Glucose
Glycolysis
ATP
Oxygen Absent
Oxygen Present
Anaerobic Respiration (Fermentation)
Aerobic Respiration

• ATP

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Aerobic Respiration

• After glycolysis, most of the energy from glucose
  remains locked in 2 molecules of pyruvate
• If oxygen is present, the pyruvate enters the
  mitochondrial matrix to complete the Krebs Cycle
• Pyruvate (3-C) is converted to Acetyl CoA (2-C)
• CO2 is released as a waste product
• NADH is produced

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The Krebs Cycle

• Yield per pyruvate molecule
• 4 NADH
• 1 FADH2
• 1 ATP
• 2 CO2
• Yield per glucose molecule (two turns of Krebs
  Cycle)
• 8 NADH
• 2 FADH2
• 2 ATP
• 6 CO2
• CO2 released as a waste product

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Electron Transport Chain

• The ETC converts the NADH and FADH2 from
  glycolysis and the Krebs Cycle into ATP
• Occurs in inner membrane of mitochondrion
• The energy in each NADH molecule moves enough
  protons (H) into the mitochondrial matrix to
  create 3 ATP
• 1 FADH2 ? 2 ATP

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The Electron Transport Chain

• The electrons from NADH and FADH2 are passed from
  one electron acceptor molecule to another.
• Each electron acceptor is more electronegative
  than the last.
• Oxygen is the final electron acceptor
• e-
• ETC

oxygen
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Chemiosmosis

• Similarly to photosynthesis, the energy the
  electrons lose along the way moves H out of the
  matrix and into the intermembrane space of the
  mitochondrion
• As H ions diffuse through the membrane, ATP
  synthase uses the energy to join ADP and a
  phosphate group ? ATP

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Oxidative Phosphorylation ETC Chemiosmosis
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Aerobic Respiration Total Energy Yield

• Glycolysis
• 2 ATP (Net)
• 2 NADH ? 6 ATP
• Krebs Cycle
• 2 ATP
• 8 NADH ? 24 ATP (ETC)
• 2 FADH2 ? 4 ATP (ETC)
• TOTAL
• 8 ATP 30 ATP ? 38 ATP