Investigation: To find the effect of the concentration amylase on the rate of breakdown of starch

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Investigation:  To find the effect of the concentration amylase on the rate of breakdown of starch.

PREDICTION

        The lower the concentration of amylase, the slower the breakdown of starch will be.  If you double the amount of amylase, the breakdown of starch will be quicker because there are twice as many active sites.

        I expect to see a graph like:  

                        Rate of

Breakdown

                           

                                        Concentration of amylase

RESEARCH

Enzymes are made of long protein molecules, which are folded up so they have an irregular globular shape.  One part of the surface is the active site and fits exactly into the substrates, which then reacts.  When a substrate molecule collides with an enzyme it becomes attached to the active site of the enzyme and the reaction then takes place.  The products then leave the active site, which can be used again.

Temperature effects the efficiency of the enzymes.  The higher the heat the greater the proportion of damage on the enzyme.  The enzyme will no longer fit in the active site. Below normal temperatures, enzymes become less and less active, due to reductions in speed of molecular movement, but this is reversible, so enzymes work effectively when returned to normal temperature.

        In digestion the substance which is present at the beginning of the experiment is called the substrate.  The substance made at the end of the reaction is called the product.  For example, in saliva there is an enzyme known as amylase (which is being used in this investigation).  It catalyses the breakdown of starch to the complex sugar maltose.  In this reaction, starch is the substrate and the maltose is the product.

DEPENDENT VARIABLES 

The dependent variables of this investigation are as follows:

  • Measurement of time in seconds to breakdown starch.
  • Amount of starch kept the same.
  • The solution will be added to the tile with iodine solution every thirty seconds using a petite pipette.  (MUST make sure that pipette is changed for different test tubes so as to avoid contamination.)
  • Stop clock must be started as soon as amylase and starch mixed together.

INDEPENDENT VARIABLE

There is only one independent variable, which is:

  • The concentration of amylase will be changed in order to test the speed of starch breakdown in different ratios of water and amylase concentration.  However, the same quantity of enzyme will be added to the same amount of starch.
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NOTE        This ratio determines how many parts water to amylase.  If the concentration is too weak then the experiment will take too long.  The ratios of water to amylase must have an equal total; in the case above the totals are 10.  The concentrations must all have the same volume and the starch must also have a definite volume.

At the end of the experiment the rate of breakdown will be plotted on a graph against the concentration of amylase.  The rate of breakdown can be worked out by the equation on the ...

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