Rate of reaction with amalayse enzyme(at different pH values)

Aim

use continous samplying with iodine soultion in order to measure the time taken for starch(substrate) to be digested by amalayse enzyme at different pH values

Equipment

-water baths

-spotting tiles

5 cm cubed measring cylinder

-syringes

-glass rod

-satrch solution

-amalasye enzyme solution

-buffered solution

-iodine soltion

-therometer

Method

1. place single drops of iodine solution in rows on the tile

2. Label a test tube with the pH to be tested

3. Use the syringe to place 2 cm³ of amylase in the test tube

4. Add 1 cm³ of pH buffer solution to the test tube using a syringe

5. Use another test tube to add 2 cm³ of starch solution to the amylase and buffer solution, start the stopwatch whilst mixing using a pipette

6. After 10 seconds, use a pipette to place one drop of the mixture on the first drop of iodine solution, which should turn blue-black

7. Wait another 30 seconds and place another drop of the mixture on the second drop of iodine

8. Repeat every 30 seconds until iodine solution remains orange-brown

9. Repeat experiment at different pH values – the less time the iodine solution takes to remain orange-brown, the quicker all the starch has been digested and so the better the enzyme works at that pH

10. Calculate the rate of reaction at each pH as 1 ÷ time taken (e.g. 1 ÷ 120 s = 0.0083 s⁻¹). The shortest time gives the fastest rate. When you write a conclusion, describe the effect on the rate or enzyme activity, not the time

Adjustment to the method

• Temperature must be controlled (it is a control variable) by using a water bath, e.g. at 35 °C

  • All solutions that need to be used (starch, amylase, pH buffers) should be placed in a water bath and allowed to reach the temperature (using a thermometer to check) before being used

• Other control variables: the volume and concentration of the amylase, starch and buffer solutions, and the volume of mixture and of iodine solution used in each test

Control investigation

Distilled water is used in order to prove that the enzyme is the reason the strach is broken down

Risk assessment

-amalayse can cause irritation when in contact with the skin and iodine can irrate our eyes and stain our clothes

be careful when using hot water bath as it can burn skin

if using a busen burner tie hair back and wear goggles

Sources of error and fixes

reation starting before the timer is pressed

once the strach and amlayase has been mixed start the time immediately