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Calorimetry - respiration action

  1. Aug 28, 2008 #1
    Hi there,

    I currently have an assignment on calorimetry. I chose to burn different kinds of potato chips and measure the energy that they produce. I am now in the process of writing up my report and I am struggling to understand the respiration reaction.

    The most common type of carbohydrate in a potato is starch. This is broken down into glucose through the digestive system, before been used in the respiration reaction to produce energy. What confuses me is that in a calirometer, there is no enzymes to break down the starch, so what is actually burning and releasing the energy?

    I guess what I am trying to ask is can starch be substituted for glucose in the respiration reaction?

    Secondly, why is there a flame if the respiration reaction occurs in humans and plants without them catching alight?

    If someone could explain what is actually going on it would be greatly appreciated.

    Many thanks,

  2. jcsd
  3. Aug 29, 2008 #2


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    Staff: Mentor

    Doesn't matter how you get from starch to CO2 and H2O, amount of energy produced is always the same.
  4. Aug 29, 2008 #3


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    The breakdown of starch has a somewhat high activation energy. In order to get over this energy barrier in the absence of enzymes, you need a flame. The enzymes in our body lower the activation energy of these processes, however, so that the thermal energy available at 37oC is sufficient to cross the barrier. Furthermore, the breakdown of starch into glucose and the metabolism of glucose occur in multiple steps (breaking the 6-carbon glucose into two 3-carbon molecules takes a total of 10 reactions). By having so many intermediate steps in the breakdown of glucose, the body can release the energy from the oxidation of glucose slowly and efficiently.
  5. Aug 29, 2008 #4
    thanks very much, I understand a lot better now.

    Also, are those 10 reactions available on the internet somewhere as my textbook doesnt cover it.
  6. Aug 29, 2008 #5


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  7. Aug 29, 2008 #6
  8. Aug 30, 2008 #7
    my teacher also told me that fatty acids and amino acids would also burn. do these undergo a respiration reaction too?
  9. Aug 30, 2008 #8
    http://en.wikipedia.org/wiki/Fatty_acid_metabolism" [Broken]

    http://en.wikipedia.org/wiki/Protein_catabolism" [Broken]
    Last edited by a moderator: May 3, 2017
  10. Aug 30, 2008 #9
    thanks Mike H
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