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Enzyme Question

  1. Feb 7, 2007 #1
    I originally posted this in the homework help section but I didn't get a response so I'm going to post it here. Please don't remove it if you are a moderator because I need this answered as soon as possible and I don't think I was gonna get an answer from the homework help section.

    1. The problem statement, all variables and given/known data
    I’m currently working on a biology lab involving enzymes. Here is some of the information concerning the lab: One of the enzymes necessary in the respiratory cycle, in which fuel molecules are ultimately reduced to carbon dioxide and water, is succinic dehydrogenase. Its specific job is to remove hydrogen from a chemical donor. Ultimately, hydrogen is transported to the acceptor molecule, oxygen.
    In the lab, three test tubes were filled with 20 mL of solution. Here are the materials in two of the test tubes:
    #2- 5 mL of 0.1 M sodium succinate solution;3.5 mL water; 10 mL yeast suspension; and 1.5 mL sodium iodoacetate plus 1.5 mL blue dye
    #3- 5 mL sodium succinate solution, 2.0 mL water; 10 mL yeast suspension; and 1.5 mL sodium iodoacetate, plus 1.5 mL blue dye
    Pretty much, after two days, test tube#2 was almost completely discoloured and turned into a clear colour while test tube#3 was only partially discoloured.
    Anyways, here are my questions concerning the lab:
    1.) What effect would iodoacetate have on the lifespan of any living cell? Explain your answer?
    2.) What purpose did iodoacetate serve in this experiment?
    3.) How does one explain the partial decolouration of test tube#3 (in which iodoacetate was present)
    4.) What factor will determine how long this partial decolouration can be maintained before tube#3 stays blue as it will at the end of the experiment?

    Also what conclusions can be drawn based on these results and observations?
    I’d really appreciate any help since most of my friends and class are lost about this lab.

    Here's what I've done so far to the above questions but am not sure if it's right:
    1.)The effect of iodoacetate will decrease the life span of any living organism such as yeast cells. Iodoacetate can affect the semi-permeable membrane of a cell by causing the cell to swell up or shrink. It can also be a metabolic inhibitor. The yeast cells in test tube#3 of this experiment died because of the presence of sodium iodoacetate.
    2.)The presence of sodium iodoacetate helps prove that yeast cells are responsible for allowing sodium succinate to produce water. The sodium iodoacetate in test tube#3 prevented all of the yeast cells present in the test tube to be reduced with sodium succinate to water. This is proven by the lack of discolouration in test tube#3 compared to the high amount of test tube#2 which did not contain sodium iodoacetate. This proves that a chemical such as sodium iodoacetate can interfere with an enzyme such as succinic dehydrogenase.
    3.)The iodoacetate prevented all of the fuel cells from being reduced to water because of its harmful effects on living cells such as yeast cells. Full instead of partial discolouration could occur in test tube#2 because of the absence of iodoacetate. Iodoacetate may also effect the pH of the solution by acting as a buffer and preventing the solution from being a clear colour. It could also denature enzymes which consist of protein.
    4.)The amount of yeast cells compared to the volume of the iodoacetate present will dictate the amount of discolouration which occurs in test tube#3. The higher the amount of yeast cells and the lower the amount of iodoacetate, the longer the discolouration occurs.
  2. jcsd
  3. Feb 8, 2007 #2


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    Staff Emeritus
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    You haven't provided enough information for anyone to help you. What was the "blue dye?" If the tubes are turning clear, it must be an indicator of some sort, but you haven't told us for what, and by just calling it a "blue dye" we wouldn't know from the name of it either. Also, why did you leave out the contents and results of tube #1? Was that a control tube that did not have iodoacetate? How can anyone help you interpret your findings without a control?

    The only difference described between tubes #2 and #3 is the amount of water added. Is that really correct? That would make the total volume in the tube different, but you still have the same amounts of succinate and iodoacetate. Please check those details.
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