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    We did an experiment in biology today investigating the effect of different respiratory substrates on yeast.
    Procedure:

    Add yeast separately to 5 different respiratory substrates (glucose, fructose, sucrose, galactose and maltose).

    Stir all 5 test tubes.

    Place them in water bath at 35 degrees.

    add paraffin layer to each tube to ensure yeast are respiring anaerobically.

    add indicator, when indicator turns pink, measure the rate of gas produced by inserting the glucose test tube into a manometer. measure the time it takes for each substrate to cause the fluid in the manometer to flow 15mm.

    Repeat for other substrates.

    My homework is to answer the following questions.

    What are the limitations for the experiment?

    I was thinking that acidic conditions could have caused the enzymes to denature.
    Therefore adding a pH buffer into each test tube to prevent enzymes becoming denatured would improve the accuracy of my results.

    I'm also thinking of a way to maintain the heat at a constant temperature.

    Suggest a suitable control.

    Is the experiment reliable?

    Ideas would be appreciated as i'm fairly stuck.
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    (Original post by Masderchef)
    What are the limitations for the experiment?

    I was thinking that acidic conditions could have caused the enzymes to denature.
    Therefore adding a pH buffer into each test tube to prevent enzymes becoming denatured would improve the accuracy of my results.

    I'm also thinking of a way to maintain the heat at a constant temperature.
    A couple of points. pH changes don't exactly 'denature' enzymes as such. They cause reversible conformational changes that can inhibit substrate binding at the active site. This is different to denaturation in that there's no permanent loss of tertiary structure. Also, acidic conditions may or may not inhibit the enzymes. Some enzymes work best in acidic conditions. Do you know the optimum pH of the enzymes? Without knowing that you can't choose a pH buffer.

    As for maintaining the heat at a constant temperature, that's what the waterbath is for
 
 
 
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