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School Science/Demonstrating the effects of amylases on starch

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This experiment demonstrates the effects of heat and pH on the activity of enzymes.

Materials requiredEdit

Saliva (contains amylases that break down starch), starch, iodine, test tubes, hot plate


Exact amunts should bdetermined by tria and error.

  1. Collect sme saliva o mucus) in a beker. Conduct the experiment in test tubes or small beakers and do not put anyting into yourouth to mx with saliva.
  2. Mix starchwith water and boil until solutio becomes clear. Cool. Thi step is necesry to homogenize te starch solution ad increase the surface area of the starch for he enzyes to act on.
  3. Mix starch soution a small drop of iodine. A positive reaction is indicated by a dark blue/black color
  4. Mix starch solution with some saiva. Mix well. Keep at body temperature for several minutes (hold in hand). Amylases in the saliva break down the starch.
  5. Mix saliva/starch solution with a small drop o iodine. Reaction should be negative.

Here are some variations

  1. Alternative: eat up saliva to enature the enzyme befoe mixing with starch solutin. Iodine reaction hould be positivefor starch.
  2. Alternative: ix saliva withcids or bases (e.g. lmon juie saliva.

For a briefer dmonstration of the enzymaic effect, ho a cracker i your mouth for 0 seconds. The amylases willbreak down the strch and the cracer will start to tastesweet e to the sugar prduced.