Aerobic Respiration - staff.camas. 8/10/2011 ¢  AEROBIC RESPIRATION Aerobic respiration is the next

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  • AEROBIC

    RESPIRATION Chapter 8

  • AEROBIC RESPIRATION Aerobic respiration is the next step after Glycolysis if the cell can

    obtain oxygen.

     We won’t need it until the last step…but we still need it.

    Remember that the final product of Glycolysis is pyruvate.

    Aerobic respiration takes place in the mitochondria

    The first step is an intermediate reaction to prepare the pyruvate for

    the citric acid cycle

     (The intermediate step is only one step, and it’s not technically part

    of Glycolysis OR aerobic respiration. It’s just a preparatory step.)

     The pyruvate gives off a carbon as CO2, donates a H to form NADH, and the

    final molecule is an acetyl-CoA molecule

  • CITRIC ACID CYCLE

    The citric acid cycle takes place in the matrix of the

    mitochondria

    **Remember: each step in aerobic respiration happens

    TWICE—once for each PGAL formed in Glycolysis

    Step 1

    Acetyl CoA (2-carbon molecule) bonds with an oxaloacetate (4-

    carbon molecule) to form citric acid (6-carbon molecule)

  • CITRIC ACID CYCLE

    Step 2

    Citric acid gives off a CO2 The molecule now contains 5-carbons

    CO2 is not needed by the cell, so it is expelled out into the blood

    stream.

    Citric acid donates a hydrogen to an NADH

    Citric acid reforms to an alpha-ketoglutarate

  • CITRIC ACID CYCLE

    Step 3

    Alpha-ketogluterate gives off a CO2, a hydrogen for an

    NADH, and a phosphate for ATP

    The molecule then forms a succinate

    The molecule is now back to the 4-carbon molecule that the

    cycle started with

  • CITRIC ACID CYCLE

    Step 4

    Succinate donates a hydrogen for an FADH2 molecule.

    The succinate then rearranges to form a molecule of

    fumerate

  • CITRIC ACID CYCLE

    Step 5

    The fumerate rearranges to form a molecule called

    malate

  • CITRIC ACID CYCLE

    Step 6

    The malate donates a hydrogen to form NADH

    The malate then reforms to the original

    oxaloacetate molecule

    The oxaloacetate begins the cycle over again.

  • CITRIC ACID CYCLE SUMMARY

    Inputs…per cycle, (per glucose)

    Acetyl CoA…1 (2)

    Outputs

    ATP… 1 (2)

    FADH2… 1 (2)

    CO2… 2 (4)

    NADH… 3 (6)

  • ELECTRON CARRIERS

    A hydrogen is simply one proton and one electron. So, when a

    “hydrogen” is donated, it is also appropriate to say an “electron” is

    donated

    Electron carriers are molecules that transport a hydrogen from one

    location to another

     Typically, the electron of the hydrogen will be used as a cofactor for an

    enzyme

    NADH and FADH2 have been synthesized multiple times so far in

    cellular respiration.

    All will finally be used in the electron transport chain as reactants

  • ELECTRON TRANSPORT CHAIN

    The electron transport chain follows glycolysis and the citric

    acid cycle.

     It is taking place at the same time as glycolysis and citric acid cycle,

    but it uses the products of glycolysis and the citric acid cycle as

    reactants

    The ETC takes place in the inner membrane of the

    mitochondria.

    The ETC is powered thanks to the concept of diffusion and

    equilibrium

     Important fact to remember: diffusion and osmosis naturally occur

    in the universe, which means that these processes happen for free.

  • ELECTRON TRANSPORT CHAIN The ETC is a series of protein channels embedded in the cristae

    (inner mitochondrial membrane).

    The NADH and FADH2 give off their electron, which powers each

    protein channel in sequence.*

     The NAD+ and FAD+ then return to pick up another electron

     *REMEMBER: If we can’t do this step, then the cell has to do fermentation instead.

    These proteins move hydrogen atoms from inside the membrane to

    outside the membrane, against the concentration gradient.

     The energy for this comes from the NADH and FADH2 electrons.

     The hydrogen that cross the membrane are already present. They never leave.

    This creates an unequal ratio of hydrogen atoms along the membrane

    (more are outside than inside). The membrane is NOT in equilibrium

  • ATP SYNTHASE The only way for the hydrogen atoms to get back across

    the membrane (and reach equilibrium) is through a specific

    channel enzyme called ATP synthase.

    ATP synthase looks like an upside-down light bulb.

    As the hydrogen atoms pass through the ATP synthase

    from the outside of the membrane to the inside, they

    provide kinetic energy to the enzyme.

    With this energy, ATP synthase attaches phosphates to

    ADP molecules in the “bulb” part, building an ATP

    molecule.

  • ATP PRODUCTION Each molecule of NADH powers the ETC enough to build 3

    molecules of ATP

     FADH gives a little less power and can build only 2 ATP

    This means the ETC can produce a total of 32-34 ATP per glucose

    molecule.

    Add that to the four ATP already produced in glycolysis and the citric

    acid cycle, you have a maximum-possible net gain of 36-38 ATP

    molecules from 1 molecule of glucose.

    With fermentation: it’s two.

    To remove the electron from the ETC, the cell bonds it with a

    molecule of oxygen and forms H2O

    This is why you need to breathe. This is what the oxygen is used

    for.

  • ETC SUMMARY

    Inputs (per molecule of glucose)

    10 NADH

    2 FADH2

    O2

    Outputs

    28-30 ATP from NADH

    4 ATP from FADH2

    NAD+

     FAD+

    H2O

  • CELL RESPIRATION SUMMARY

    C6H12O6 + 6 O2  6 CO2 + 6 H2O + Energy

    C6H12O6 : For glycolysis

    6 O2 : To collect the electron in the ETC

    6 CO2 : Given off in intermediate step and Citric Acid Cycle

    6 H2O : Given off in the ETC

    Energy : In the form of ATP