How pH Affects the Break Down of Starch by the Enzyme Amylase

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How pH Affects the Break Down of Starch by the Enzyme Amylase


The optimum pH for the reaction of starch with amylase is pH 7. PH values lower or higher than this value will result in a slower rate of reaction. Amylase works in the range pH 3 to pH 11.

Biological Knowledge ====================

PH changes affect the structure of an enzyme molecule and therefore affect its ability to bind with its substrate molecules. Changes in pH affect the ionic bonds and hydrogen bonds that hold the enzyme together, which naturally affects the rate of reaction of the enzyme with the substrate. On top if this, the hydrogen ions neutralise the negative charges of the R groups in the …show more content…

7 Corvettes

These are used instead of test tubes as corvettes are required if a colorimeter is to be used. One corvette is needed for each pH and one for the control. These can then be reused for the repeats.

Syringe calibrated at 0.1 cm³ intervals

This is vital to measure out the volumes of the starch and amylase solutions accurately using these calibrations to achieve precision. This apparatus is far more accurate than using a measuring cylinder, as there are minimal transference losses.

2 Syringes

As the volume of buffer solution of iodine is not being measured, only the number of drops, apparatus with calibrations is not required for this.


This is important for measuring the time. It is not important whether a digital or traditional stopclock is used as there will be the same percentage error either way.


* Measure out 1 cm³ amylase solution with calibrated syringe and put in corvette

* Add to this 5 drops of pH 4 buffer solution

* Measure out 2 cm³ starch solution

* Start stopclock and leave for 1 minute

* Measure out 1 cm³ amylase and place in second corvette

* Add to this 2 cm³ distilled water

* Add 3 drops of iodine solution

* Shake it well,

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