Required practical: pH and amylase

Question 1

Aim of this experiment

Answer 1

To record how long it takes for different pHs of amylase to digest starch
And to find this out by seeing how many wells it takes for the iodine to remain brown = no starch because it has been digested

Question 2

Step 1

Answer 2

Place 1 drop of iodine solution (brown) into each well of a spotting tile

Question 3

Step 2

Answer 3

Get 3 test tubes.
One = 2cm³ of starch solution
One = 2cm³ of amylase solution
One = 2cm³ of pH 5 buffer solution

Question 4

Step 3

Answer 4

Place all test tubes in a water bath at 30°c for 10 mins
Allows to get to the right temperature as a control
Because temperatures can affect rate of digestion

Question 5

Step 4

Answer 5

Combine the 3 solutions then return them to the water bath.

Begin a stop watch

Question 6

Step 5

Answer 6

Every 10 seconds, add one drop of this solution to a spot in the iodine solution
This turns blue/black as starch is present

Question 7

Step 7

Answer 7

Repeat with pH buffer of 6, 7 and 8

Question 8

Step 6

Answer 8

Notice when the iodine remains brown
This shows us there is no longer starch in the solution as the reaction is complete and it has been broken down into simple sugars

Question 9

Conclusion

Answer 9

It took less spots for pH 7 to fully complete the reaction

This shows that the optimum pH for amylase to work is 7/neutral

Question 10

Problems with the experiment

Answer 10

Taking samples at 30 secs = only approximate idea as to when reaction is complete
Moment when iodine stays brown isn’t always obvious: colour change is gradual and mixed

Question 11

Independent variable

Answer 11

pH of the pH buffer solution

Question 12

Dependent variable

Answer 12

Time taken for amylase to digest starch solution

Question 13

Control variables

Answer 13

Temperature, volume of starch, volume of amylase, concentration of amylase and starch