Cellular Respiration

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• 6O2 C6H1206 6CO2 6H2O
  energy

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Cellular Respiration

• Biology
• Mrs. Volin

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Cellular Respiration

• The process of breaking down food molecules in
  the presence of oxygen

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Photosynthesis and Cellular Respiration Whats
the connection?
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When food is broken down, energy
is released.

• One way of measuring energy is in calories.
• One calorie
• Amount of energy it takes to raise the
  temperature of 1 gram of water 1 degree Celsius.
• A Calorie in food labeling refers to
• 1000 calories.

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• 6 O2 C6H1206 6 CO2 6 H2O
  ENERGY
• Cellular Respiration
• Requires oxygen
• Requires food
• Gives off carbon dioxide
• Gives off water
• Gives off energy
• Energy must be released a little bit at a time.
• Cells trap this energy and make ATP

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3 Steps to Cellular Respiration

• Glycolysis
• breaking sugar (Greek)
• Krebs cycle
• Electron transport chain

In cytoplasm
In mitochondria
In mitochondria
Each step captures some chemical energy and uses
it to produce ATP.
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Glucose
Krebs cycle
Electrontransport
Glycolysis
Alcohol or lactic acid
Fermentation (without oxygen)
Go to Section
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Glycolysis

• First step in cellular respiration
• Takes place in the cytoplasm of the cell
• Glucose is broken into 2 molecules of pyruvic
  acid.

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Figure 92 Respiration An Overview
Section 9-1
Mitochondrion
Electrons carried in NADH
Electrons carried in NADH and FADH2
Pyruvic acid
Glucose
Electron Transport Chain
Krebs Cycle
Glycolysis
Mitochondrion
Cytoplasm
Go to Section
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Figure 93 Glycolysis
Section 9-1
Glucose
2 Pyruvic acid
To the electron transport chain
Go to Section
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Figure 93 Glycolysis
Section 9-1
Glucose
2 Pyruvic acid
To the electron transport chain
Go to Section
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Figure 93 Glycolysis
Section 9-1
Glucose
2 Pyruvic acid
To the electron transport chain
Go to Section
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Two possible pathways after glycolysis

• If O2 is present Krebs Cycle
• (continue cellular respiration)
• If O2 is not present fermentation

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Fermentation

• Because fermentation does not require oxygen, it
  is anaerobic.

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Two types of Fermentation

• Lactic acid fermentation
• Alcoholic fermentation

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Figure 94 Lactic Acid Fermentation
Section 9-1
Lactic acid
Glucose
Pyruvic acid
Go to Section
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Figure 94 Lactic Acid Fermentation
Section 9-1
Lactic acid
Glucose
Pyruvic acid
Go to Section
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Figure 94 Lactic Acid Fermentation
Section 9-1
Lactic acid
Glucose
Pyruvic acid
Go to Section
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Lactic Acid Fermentation

• In muscles, the buildup of lactic acid causes
  painful, burning sensation

Muscle cells run out of oxygen. Cells produce
ATP for energy by lactic acid fermentation
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Oxygen debt

• Oxygen debt Extra oxygen must be taken in to
  metabolize the lactic acid
• Heavy breathing during and after exercise repays
  the oxygen debt

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(net)
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Alcoholic Fermentation

• Used in baking, brewing, and production of
  pharmaceuticals

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The Krebs Cycle and Electron Transport
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Cellular Respiration Flowchart
Section 9-2
Glucose(C6H1206) Oxygen(02)
Glycolysis
KrebsCycle
ElectronTransportChain
Carbon Dioxide (CO2) Water (H2O)
Go to Section
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Krebs Cycle takes place in the mitochodrial
matrix in eukaryotes
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Krebs Cycle

• Takes place within the mitochondrial matrix in
  eukaryotes
• In the cytoplasm in prokaryotes

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Krebs Cycle or Citric Acid Cycle

• Hans Krebs, German physician and researcher
• Worked out the details in 1937
• Received Nobel Prize in 1953

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Figure 96 The Krebs Cycle
Section 9-2
Citric Acid Production
Mitochondrion
Go to Section
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Figure 96 The Krebs Cycle
Section 9-2
Citric Acid Production
Mitochondrion
Go to Section
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pyruvic acid
CO2
Pyruvic acid from glycolysis enters
mitochondria Pyruvic acid is converted to
Acetyl-CoA and further converted to citric
acid Citric acid (citrate) breaks down to a 5-C
compound then a 4-C compound Along the way, 2
CO2 released, 1 NADH and 1FADH2 are formed 1 ATP
formed ------------------------------ Total
energy yield 4 NADH , 1 FADH2, 1
ATP

NAD NADH
The Krebs Cycle
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Figure 97 Electron Transport Chain
Section 9-2
Electron Transport
Hydrogen Ion Movement
Channel
Mitochondrion
Intermembrane Space
ATP synthase
Inner Membrane
Matrix
ATP Production
Go to Section
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The Totals

• Glycolysis 2 ATP per glucose molecule
• Krebs Cycle and Electron Transport
• 34 ATP per glucose
• TOTAL 36 ATP
• 62 of the energy in glucose is given off as heat

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Photosynthesis vs Cellular Respiration

• Photosynthesis deposits energy
• Cellular respiration withdraws energy
• Products of photosynthesis are the reactants for
  cellular respiration
• Products of cellular respiration are the
  reactants for photosynthesis

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Photosynthesis vs Cellular Respiration

• Cellular respiration in both eukaryotes and
  prokaryotes
• Photosynthesis only in plants, algae, and some
  bacteria

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• 2 ATPs needed in first step
• (an investment)
• 4 e- removed by NAD and NADH is produced
• 4 ATPs produced
• ______________________________net 2 ATP and 2
  NADH
• The amount of energy yielded from glycolysis is
  small.

NAD in cells can be used up quickly. Without
more NAD to carry electrons, glycolysis would
stop and ATP production would stop
pyruvic acid
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Fermentation

• Energy (ATP) is released
• No O2 present.

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Alcoholic Fermentation

• Waste products are
• ethyl alcohol
• carbon dioxide
• Equation for fermentation after glycolysis
• pyruvic acid NADH alcohol CO2 NAD

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Lactic Acid Fermentation

• Pyruvic acid is converted to lactic acid
• NAD is regenerated so that glycolysis continues
• Equation for lactic acid fermentation after
  glycolysis
• pyruvic acid NADH lactic acid NAD

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• The amount of energy yielded from glycolysis is
  small-----
• 90 of the chemical energy in glucose is still
  tied up in pyruvic acid
• To extract the remaining energy from pyruvic
  acid, OXYGEN is required (a powerful
  electron acceptor)

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Cellular Respiration is aerobic

• Pathways of cellular respiration require oxygen
• In the presence of oxygen, pyruvic acid from
  glycolysis enters the Krebs cycle

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Krebs Cycle

• Pyruvic acid is broken down into CO2
• Series of steps yields energy
• Also called citric acid cycle because first
  compound formed in cycle is citric acid

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Krebs Cycle

• 4 NADH each carry a pair of high energy
  electrons. FADH2 carries a pair of high energy
  electrons.
• In the presence of O2----HUGE amounts of ATP will
  be generated in electron transport chain

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Electron Transport Chain

• In the inner membrane of the mitochondria in
  eukaryotes
• In the cell membrane of prokaryotes
• Series of carrier proteins
• High energy e- are used to convert ADP to ATP

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• Electrons passed from one carrier to another.
• At the end of chain, O2 is the final acceptor of
  electrons and H
• Each time e- are handed over to another carrier,
  H moves across membrane.
• Intermembrane space becomes positively charged

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• H pass through ATP synthase molecules in
  membrane.
• Rotation of ATP synthase provides energy to add a
  P-group to ADP
• FORMS ATP
• Each pair of electrons converts 3 ADPs to 3 ATPs