Cellular Respiration: Harvesting Chemical Energy

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Cellular Respiration Harvesting Chemical Energy
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Respiration is the process of extracting stored
energy from glucose and storing it in the high
energy bonds of ATP.
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Cellular Respiration Equation
Reactants
Products

• C6H12O6 6 O2 6 CO2 6 H2O
  and energy
• As a result of respiration, energy is released
  from the chemical bonds and used for
  phosphorylation of ATP.
• Phosphorylation is the process of adding a
  phosphate group to a molecule. By adding a
  phosphate ADP it becomes ATP.
• The respiration reactions are controlled by
  ENZYMES.

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Cellular Respiration

• There are two types of Respiration Anaerobic
  Respiration and Aerobic Respiration
• Some organisms use the Anaerobic Respiration
  pathway, and some organisms use the Aerobic
  Respiration pathway.

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Anaerobes

• Anaerobes are organisms that use the Anaerobic
  Respiration pathway
• Most anaerobes are bacteria (not all).
• Anaerobes do NOT require oxygen.

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Aerobes

• Aerobes are organisms that use the Aerobic
  Respiration pathway.
• Aerobes require oxygen.

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Anaerobic Respiration

• Anaerobic Respiration does
• NOT require oxygen!
• The 2 most common forms of Anaerobic Respiration
  are
• 1. Alcoholic Fermentation, and
• 2. Lactic Acid Fermentation

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The First Stage of Respiration for ALL living
organisms, anaerobes or aerobes, is called
Glycolysis and takes place in the Cytosol.
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Glycolysis

• glyco means glucose/sugar, and
• lysis means to split. Therefore,
• glycolysis means to split glucose
• This process was likely used to supply energy for
  the ancient forms of bacteria.

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Glycolysis

• Function - to split glucose and produce NADH, ATP
  and Pyruvate (pyruvic acid).
• Location - Cytosol
• Occurs in 9 steps- 6 of the steps use magnesium
  (Mg) as a cofactor.

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Glycolysis
4 ATPs are produced
Pyruvic Acid (3 Carbons)
Glucose (6 carbons)
2 ATPs supply the activation energy
Pyruvic Acid (3 Carbons)
2 NAD 2 e- 2 NADH
4 ATP Yield 2 ATP Net Gain
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Products of Glycolysis

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

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Alcoholic Fermentation

• is carried out by yeast,
• a kind of fungus.

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Alcoholic Fermentation

• Uses only Glycolysis.
• Does NOT require O2
• Produces ATP when O2 is not available.

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Alcoholic FermentationC6H12O6
2 C2H5OH 2 CO2
(Ethyl Alcohol or Ethanol)
As a result of Alcoholic Fermentation, Glucose
is converted into 2 molecules of Ethyl Alcohol
and 2 Molecules of Carbon Dioxide.
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Alcoholic Fermentation
Glycolysis
Released into the environment
4 ATPs are produced
CO2
(C2H5OH)
Pyruvic Acid (3C)
Ethyl Alcohol (2C)
Glucose (6 carbons)
Released into the environment
CO2
Pyruvic Acid (3C)
2 ATPs supply the activation energy
Ethyl Alcohol (2C)
(C2H5OH)
2 NAD 2 e- 2
NADH 2 NAD 2 e-
4 ATP Yield 2 ATP Net Gain
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Question

• Why is the alcohol content of wine always around
  12-14?
• Because Alcohol is toxic and kills the yeast at
  high concentrations.
• Oh Yeah..The Holes in Swiss Cheese are bubbles
  of CO2 from fermentation.

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Importance of Fermentation

• 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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Lactic Acid Fermentation

• Uses only Glycolysis.
• Does NOT require O2
• Produces ATP when O2 is not available.

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Lactic Acid Fermentation

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

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Lactic Acid Fermentation
Glycolysis
4 ATPs are produced
Pyruvic Acid (3C)
Lactic Acid (3C)
Glucose (6 carbons)
Pyruvic Acid (3C)
2 ATPs supply the activation energy
Lactic Acid (3C)
2 NAD 2 e- 2
NADH 2 NAD 2 e-
4 ATP Yield 2 ATP Net Gain
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Fermentation - Summary

• Releases 2 ATP from the breakdown of a glucose
  molecule
• Provides ATP to a cell even when O2 is absent.

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Aerobic Respiration

• Aerobic Respiration
• requires oxygen!

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There are three phases to Aerobic Respiration ...
they are

• 1. Glycolysis (same as the glycolysis of
  anaerobic respiration)
• 2. Krebs cycle (AKA - Citric Acid cycle)
• 3. Oxidative Phosphorylation and The Electron
  Transport Chain

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Phase One Glycolysis(takes place in the
cytoplasm)
Glycolysis
4 ATPs are produced
Pyruvic Acid (3C)
Glucose (6 carbons)
Pyruvic Acid (3C)
2 ATPs supply the activation energy
2 NAD 2 e- 2
NADH
4 ATP Yield 2 ATP Net Gain
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• In order for Aerobic Respiration to continue the
  Pyruvic acid is first converted to Acetic Acid by
  losing a carbon atom and 2 oxygens as CO2.
• The Acetic acid then must enter the matrix region
  of the mitochondria. The CO2 produced is the CO2
  animals exhale when they breathe.

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Phase Two The Krebs Cycle(AKA the Citric Acid
Cycle)
Once the Acetic Acid enters the Matrix it
combines with Coenzyme A to form a new molecule
called Acetyl-CoA. The Acetyl-CoA then enters the
Krebs Cycle.
CoA breaks off to gather more acetic acid. The
Acetic acid is broken down.
Sir Hans Adolf Krebs
Produces most of the cell's energy in the form of
NADH and FADH2 not ATP Does NOT require O2
3H
3 NADH
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• Summary
• As a result of one turn of the Krebs cycle the
  cell makes
• 1 FADH2
• 3 NADH
• 1 ATP
• However, each glucose produces two pyruvic acid
  molecules. So the total outcome is
• 2 FADH2
• 6 NADH
• 2 ATP

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Comparing Aerobic and Anaerobic Respiration

• Aerobic Respiration-
• requires a mitochondrion and oxygen
• is a three phase process
• Anaerobic
• does not require oxygen
• consists of one phase only-Glycolysis

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Strict vs. Facultative Respiration

• Strict - can only carry out Respiration only
  one way aerobic or anaerobic. Ex - you
• Facultative - can switch respiration types
  depending on O2 availability. Ex yeast
• Aerobes organisms that require oxygen
• Anaerobes - organisms that DO NOT require oxygen
• Obligate Anaerobes oxygen is LETHAL to these
  organisms
• Facultative organisms that can live with or
  without oxygen

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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 (2 ATPs) is used to shuttle the NADH
  from Glycolysis into the mitochondria..So, some
  biologists teach there is an actual ATP yield of
  36 ATPs per glucose.