Cellular Respiration

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Cellular Respiration
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Cellular Respiration The Big Picture

• We are energy beings cellular respiration is
  the process by which we gain energy.
• We normally run aerobic cellular respiration in
  which we harvest energy from organic compounds
  using oxygen (O2).
• The molecule of choice for fuel is glucose.
• C6H12O6 6O2 ? 6CO2 6H2O
• Glucose has an abundance of energy in its bonds.
  We must release it in a series of small REDOX
  reactions so the energy that is released does not
  increase cell temperature too much or the
  proteins may freak out!

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Cellular Respiration The Big Picture

• There are a variety of ways to carry out cellular
  respiration and not all of them require oxygen to
  assist in the breakdown of glucose.
• Obligate Aerobes They require oxygen to oxidize
  organic molecules to make energy.
• Obligate Anaerobes They oxidize inorganic
  molecules without oxygen to gain energy. (O2
  kills!)
• Facultative Anaerobes They oxidize inorganic
  molecules with or without oxygen.
• Note the type of molecule being oxidized
  organics give big energy boosts while inorganics
  do not yield much energy.

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Cellular Respiration The Details

• AKA The Hard Part!

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Cellular Respiration The Details

• Aerobic cellular respiration is as follows
• C6H12O6 6O2 ? 6CO2 6H2O
• From this, we can gather that
• cellular respiration involves breaking the bonds
  in glucose to make six carbon dioxide molecules.
• the hydrogens get torn off of glucose to make
  water.
• the free energy released in the breakdown of
  glucose is harnessed to make ATP.
• So how do we do these jobs?

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The Reactions Well See

• There are several types of reactions that we will
  encounter along the way.
• REDOX Electrons being taken from one and added
  to another.
• Phosphorylation/Dephosphorylation The
  adding/removal of a phosphate group (PO4).
• Carboxylation/Decarboxylation The
  adding/removal of a carbon.
• Hydration/Dehydration - The adding/removal of a
  water molecule (H2O).
• Isomerization Making a molecule into its isomer
  same parts, different arrangement.

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Order of Operations

• Here is what we have to doin order
• Glycolysis Cytosol Glucose splitting.
• Pyruvate Oxidation Matrix Connect to Krebs a
  la pyruvate ? Acetyl-CoA
• Krebs Cycle Matrix Energy given off mainly
  as NADH and FADH2.
• Electron Transport Chain (ETC) Mitochondrial
  inner membrane NADH FADH2 give their energy
  to the ETC to create a proton problem.
• Chemiosmosis Mitochondrial inner membrane We
  solve the proton problem and get a big bunch of
  ATP while were at it.

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Glycolysis

• Glycolysis means sugar splitting. It occurs in
  the cytoplasm.
• Glucose goes through a series reactions that see
  it eventually turning into two pyruvate
  molecules. These will go on to the next stage.
• We get a net gain of 2 ATP and 2 NADH. The ATP
  are ready to use and the NADH goes in our back
  pocket for later.
• Overall
• Glucose ??? 2 Pyruvate
• (2 ATP 2 NADH)

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2. Pyruvate Oxidation

• The pyruvate goes into the mitochondrion and
  makes it way to the matrix.
• Once in the matrix, the pyruvate is oxidized and
  turned into Acetyl-CoA (which will start the next
  stage).
• Along the way, a NAD becomes an NADH which we
  will put in our back pocket for later.
• Glucose gave us 2 pyruvate so we will end up with
  2 Acetyl-CoA and 2 NADHs.
• Overall
• 2 Pyruvate ? 2 Acetyl-CoA (2 NADH)

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Pyruvate Oxidation

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3. Krebs Cycle

• The two Acetyl-CoA molecules made by the previous
  stage now enters a cyclical series of reactions
  called the Krebs cycle.
• For each glucose, the Krebs cycle turns twice
  and we will get
• 2 ATP
• 6 NADH
• 2 FADH2
• The ATP are used immediately and the NADH and
  FADH2 molecules will go in our back pocket for
  later.

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The Krebs Cycle

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4. The Electron Transport Chain

• The ETC is basically a conga line of REDOX
  reactions pass the electrons to the right
  everybody! It all takes place on the
  mitochondrial inner membrane.
• Electrons from NADH and FADH2 are passed into the
  chain and are handed down the line hitting
  proton pumps along the way.
• The proton pumps take protons (H) from the
  matrix and pump them across the membrane into the
  intermembrane space of the mitochondrion.
• This is a problem as an electrostatic pH
  gradient is set up which is no good for the
  mitochondrion.
• NADH operates 3 proton pumps while FADH2 operates
  just 2 proton pumps.

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5. Chemiosmosis

• Most texts put this step and the ETC together as
  one for good reason.
• The proton problem created by the ETC is relieved
  by an enzyme, found embedded in the mitochondrial
  inner membrane, called ATP Synthase.
• ATP Synthase allows the protons (H) to come back
  into the mitochondrion were saved!
• But wait!It gets betterATP synthase fixes the
  problem and in doing so, it makes ATP!
• Its like a carpenter saying, Yeah, I can fix
  your roof but you have to let me pay you for it!.

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The ETC ATP Synthase
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The ATP Balance Sheet

• Heres how we get the 36 ATP from one molecule of
  glucose.
• 1 ATP 1 ATP (ATP is ATP already!)
• 1 NADH 3 ATP (goes through 3 H pumps)
• 1 FADH2 2 ATP (goes through 2 H pumps)
• This gives us 38 ATP! What the?!?!?
• The trick is the 2 NADHs made in glycolysis in
  the cytosol. They have to get into the
  mitochondrion first and when they enter it, they
  are converted into FADH2s.
• So what is the bottom line?

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The Bottom Line!
Stage of Cellular Respiration Molecule Produced of ATP Produced
Glycolysis 2 ATP 2 ATP
Glycolysis 2 NADH ? 2 FADH2 4 ATP
Pyruvate Oxidation 2 NADH 6 ATP
Krebs Cycle 2 ATP 2 ATP
Krebs Cycle 6 NADH 18 ATP
Krebs Cycle 2 FADH2 4 ATP

THE GRAND TOTAL THE GRAND TOTAL 36 ATP
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• FIN
• (You worked hard nice job!)