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Harvesting Chemical Energy

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					Harvesting
 Chemical
  Energy
It's a very thin horse



   ●   Do you think it’s a fast
       horse?
   ●   Do you think it’s a
       healthy horse?
   ●   What does it need?
      Photosynthesis
● What's a cow made of?
● What does a cow eat?


● How come cows are not

  green?
●   Cellular respiration
     process   in which cells make
        ATP by breaking down
        organic compounds
       Both autotrophs and heterotrophs use cellular
        respiration
               What’d he just say?
How Cells Release Stored Energy
                   ●    An Africanized
                       honey bee can fly
                       from Bloomfield to
                       well past Sandy
                       Hook on a bellyful
                       of nectar
                   ●   Where did the
                       energy come from?
Overview of Cellular Respiration
        Overview of Cellular Respiration
●   Two stages:
       Glycolysis: organic compounds converted to pyruvate
          Anaerobic
          In the cytoplasm


         ● Small amounts ATP, NADH released




       Aerobic respiration: pyruvate broken down in presence
        of O2
          In the mitochondrion
         ● NADH->large amounts of ATP
Comparisons of the main types of
  energy-releasing pathways
                ●   Early atmosphere:
                    little oxygen
                ●   Anaerobic pathways
                    used:
                       Fermentation
                       Anaerobic e- transport
                ●   When oxygen
                    starved, human cells
                    use anaerobic paths
Fermentation
      ●   All respiration starts
          with glycolysis
      ●   If oxygen not available,
          pyruvate can enter other
          pathways
      ●   Fermentation is a
          combination of glycolysis
          and certain anaerobic
          pathways
Alcoholic Fermentation
Lactic Acid Fermentation
Aerobic Respiration
          ●   Two major stages:
                 Krebs cycle
                 Electron transport
                  chain
          ●   Take leftovers from
              glycolysis and move
              them here
                 What were the left
                  overs?
Aerobic Respiration
          ●   Initial step in
              mitochondrial matrix:
                 Pyruvate reacts with
                  CoA to form acetyl
                  CoA
                 1 carbon lost as CO2
                 NAD+ reduced to
                  NADH
Aerobic Respiration
          ●   Krebs cycle occurs in
              mitochondrial
              matrix

          ●   The electron transport
              chain is located on
              the inner membrane
The Krebs Cycle
    Aerobic Respiration: Recap
●   For each glucose molecule:
       Glycolysis:
         ●   2 NADH
       Preparatory steps converting pyruvate before
        Krebs cycle:
         ●   2 NADH
       Krebs cycle:
         ● 2 FADH2
         ● 6 NADH


       Total coenzymes sent to 3rd stage:
         ●   2 FADH2, 10 NADH per glucose molecule
Electron transport chain and
       chemiosmosis
              ●   Electron transport
                  systems and ATP
                  synthase needed
              ●   Both of the above
                  found in the inner
                  membrane of the
                  mitochondrion
              ●   Both interact with
                  hydrogen and
                  electrons
Electron Transport Chain and
       Chemiosmosis
               ●   Unbound H+ shuttled
                   to outside of inner
                   membrane, creating a
                   gradient
               ●   H+ flow through ATP
                   synthases, driving
                   ATP formation
               ●   Oxygen withdraws
                   spent electrons and
                   H+-->water
Electron Transport Chain and
       Chemiosmosis

               ●   Summary of energy
                   harvest:
                      32 ATP from 3rd stage
                      2 ATP from glycolysis
                      2 ATP from 2nd stage
                      Total: 36 ATP!
                      About 39% of energy
                       from glucose
                       captured; much lost
                       as heat
Electron Transport Chain and
       Chemiosmosis

               ●   Importance of
                   oxygen:
                      Without final electron
                       acceptor, whole chain
                       stops!
Efficiency of Cellular Respiration
                 ●   Maximum yield of
                     aerobic respiration is
                     38 molecules of ATP
                     per glucose molecule
                 ●   Each ATP about 7
                     kcal
                 ●   Complete oxidation of
                     glucose releases 686
                     kcal
Efficiency of Cellular Respiration

                  ●   Car engine only about
                      25% efficient in
                      extracting energy
                      from
                      gasoline

                  ●   Our cells are about
                      39% efficient!
Summary of Cellular Respiration
Summary of Cellular Respiration
Summary of Cellular Respiration
●   Glycolysis:
       Glucose is converted into pyruvic acid, producing a
        small amount of ATP and
        NADH

●   Aerobic respiration:
       Pyruvic acid is converted into CO2 and water in the
        presence of oxygen producing a large amount of
        ATP

●   C6H12O6 + 6O2 -> 6 CO2 + H2O + energy (ATP)

				
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posted:8/26/2012
language:English
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