Cellular Respiration (2)

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Cellular Respiration (2)
The Details ?
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The Overall Equation for Cellular Respiration

• A common fuel molecule for cellular respiration
  is glucose

Glucose
Oxygen
Carbon dioxide
Water
Energy
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Redox Reactions

• Oxidation-reduction reactions chemical
  reactions that transfer electrons from one
  substance to another
• Shortened to redox reactions
• ?The loss of electrons during a redox reaction
  is called oxidation
• ?The acceptance of electrons during a redox
  reaction is called reduction
• (LEO the lion says GER!!)

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Oxidation
Glucose loses electrons (and hydrogens)
Glucose
Oxygen
Carbon dioxide
Water
Reduction
Oxygen gains electrons (and hydrogens)
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Metabolic Pathway

• A series of chemical reactions in cells (building
  up or degradation)
• Cellular respiration is an example of a metabolic
  pathway

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Overview of Cellular Respiration

• Stage One Glycolysis
• Stage Two Krebs Cycle
• Stage Three Electron Transport Chain

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Stage 1 Glycolysis

• a series of enzyme-catalyzed chemical reactions
  that breaks down glucose, forms pyruvic acid
  (pyruvate) and creates energy in the form of ATP.
• This stage does not require oxygen and takes
  place in the cytoplasm.
• ATP energy is used to start the process of
  glucose oxidation (break down).

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GLYCOLYSIS

• A 6-carbon molecule (glucose) is split into two
  3-carbon molecules (PGAL).
• 2 molecules of pyruvic acid are produced for each
  glucose molecule broken down
• Pyruvic acid now moves towards the mitochondria.

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Glycolysis

• The 3-carbon molecules now enter the
  energy-payoff phase.
• Chemical bonds are broken, and NAD picks up
  electrons and hydrogen ions, forming NADH.
• The energy released is used to attach phosphate
  groups. The phosphates are transferred to ADP,
  finally making some ATP.
• A couple more reactions rearrange the atoms in
  the 3-carbon molecules. More ATP is generated in
  the final reaction that yields pyruvic acid.
• For each glucose molecule broken down during
  glycolysis, a net of two ATPs are formed along
  with two NADH molecules.

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2 Pyruvic acid
Glucose
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Stage 2 Krebs Cycle

• The Krebs cycle completes the breakdown of sugar
• Pyruvic acid from glycolysis is changed into a
  usable form, Acetyl-CoA

2
CoA
1
3
Acetic acid
Acetyl-CoA (acetyl-coenzyme A)
Pyruvic acid
Coenzyme A
CO2
Figure 6.10
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Stage 2 Krebs Cycle

• The cycle generates 1 ATP per turn of acetyl co-A
  
• Also called the Citric Acid cycle (CAC)
• Most of the chemical energy is transferred during
  the redox reactions of NAD and FAD.
• NADH and FADH2 shuttle their cargo of high energy
  electrons to the ETC.
• What is FADH2?
• Another energy carrier like NADPH
• FAD (Flavin adenine dinucleotide) is a cofactor
  in the enzymes glucose oxidase.
• FADH and FADH2 are reduced forms of FAD.

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Input
Output
2
Acetic acid
1
2 CO2
ADP
3
Krebs Cycle
3 NAD?
4
FAD
5
6
Figure 6.11
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Stage 3 ELECTRON TRANSPORT CHAIN (ETC)

• The molecules of ETC are built into the inner
  membranes of mitochondria
• Is a series of proteins between which electrons
  are transferred which releases energy.
• In the ETC, higher energy forms NADH and FADH2
  are cashed in, producing ATP.
• The last electron receptor is O2 (it is what
  makes the process aerobic).

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Protein complex
Electron carrier
Inner mitochondrial membrane
Electron flow
ATP synthase
Electron transport chain
Figure 6.12
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Step ATP NADH FADH2

Total
ATP produced

2
2
0
Glycolysis
Transition Reaction
0
2
0
Krebs Cycle
2
2
6
4
10
2
4
4
30
Total production of ATP 38 molecules
Aerobic Cellular Respiration
C6H12O6 6O2 ? 6CO2 6H2O 38 ATP
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A Road Map for Cellular Respiration
Cytosol
Mitochondrion
High-energy electrons carried mainly by NADH
High-energy electrons carried by NADH
Glycolysis
Krebs Cycle
2 Pyruvic acid
Electron Transport
Glucose
Figure 6.7
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Adding Up the ATP from Cellular Respiration
Mitochondrion
Cytoplasm
Glycolysis
Krebs Cycle
2 Acetyl- CoA
2 Pyruvic acid
Electron Transport
Glucose
Maximum per glucose
Figure 6.14
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• PHOTOSYNTHESIS RESPIRATION
• Where? In cholorophyll-bearing cells In all
  cells
• When? In the presence of light All the time
• Input? Carbon dioxide and water Reduced carbon
  compounds and oxygen
• Output? Reduced carbon compounds, Carbon dioxide
  and water
• oxygen, and water
• Energy sources? Light Chemical bonds
• Energy result? Energy stored Energy released
• Reaction ? Reduction of carbon Oxidation of
  carbon compounds compounds
• Energy carrier(s) NADP NAD and FAD