REQUIRED PRACTICAL 5:effect on pH on amylase

Question 1

what chemical do we use to test for the presence of starch?

Answer 1

Iodine

Question 2

describe fully how to test for the presence of starch in food

Answer 2

j

Question 3

describe fully how to investigate the effect of pH on the enzyme amylase

Answer 3

1. Place one drop of iodine solution into each well of a spotting tile

2. take 3 testubes and in the first test tube put
•2cm^3 of starch solution 
in the second test tube put 
•2cm^3 of amylase solution
in the third test tube put 
•2cm^3 of pH 5 buffer solution 

3. place all three testubes in a water bath at 30°C. leave them for 10mins to allow the solutions to reach the correct temperature.
4. Now combine the 3 solutions into 1 test tube and mix with a stirring rod.
5. Put the test tube immediately back into the water bath and start a stopwatch
6. After thirty seconds, use the stirring rod to transfer one drop of solution to a well in the spotting tile which contains iodine
7. the iodine should turn blue-black, showing that starch is present
8. We take a sample every 30 seconds and we continue until the iodine remains orange
9. when the iodine remains orange, this tells us that starch is no longer present( the reaction has completed) we then record the time for this in our results
10. we now repeat the whole experiment many times using different pH buffers for example pH 6,7 and 8

Question 4

what are buffet solutions used for in biology?

Answer 4

to control the pH

Question 5

why do we leave the three test tubes in a water bath for 10 mins

Answer 5

to allow solutions to reach the correct temperature

Question 6

what are some problems with this experiment? add the solution too

Answer 6

PROBLEM = we are only taking samples every thirty seconds meaning we only have an approximate time for the reaction to complete
SOLUTION = we could address this by taking samples every ten seconds 

PROBLEM =
we are looking for the time when iodine does not go blue-black, this isn’t always obvious. The colour change tends to be gradual. Some wells might have a small amount of blue-black mixed with orange, so it can be difficult to sed when the reaction is finished
SOLUTION = Ask some people go look at the spotting tile and decide when the reaction has completed