Biology Required Practical - Enzymes

Question 1

Aim of investigation:

Answer 1

To determine the time taken to completely digest a starch solution. You will repeat the experiment at different pH levels to investigate how pH affects the time taken for this enzyme controlled reaction to occur

Question 2

Equipment required for this investigation: [14]

Answer 2

1. Test tubes
2. Test tube rack
3. Water bath
4. Spotting tiles
5. 5cm^3 measuring cylinder
6. Syringe
7. glass rod
8. stopwatch
9. starch solution
10. amylase solution
11. amylase solution
12. buffered solution
13. iodine solution
14. Thermometer

Question 3

Method for this investigstion:

Answer 3

1. On a tile, label each well with the time [ 0 onwards] and add a drop of iodine solution to each well.
2. Add 2cm^3 of each buffer solution with a syringe, into each labelled test tube.
3. Immerser the starch solution, amylase solution and the test tubes of buffer solution in a water bath of 25 degrees Celsius.
4. Allow a few minutes for the temperature to equilibrate.
5. Use a syringe to add 2cm^3 of amylase into a test tube.
6. Use a syringe to add 2cm^3 of starch into the same test tube.
   Start the timer.
7. Use the glass rod to transfer a drop of the mixture to the well labelled ‘0’ on the tile.
8. Repeat step 6 every 30 seconds, rinsing the glass rod every time, until the iodine solution remains brown and doesn’t turn blue.
9. Calculate the rate of enzyme reaction by using equation

1/[time taken for iodine solution to remain brown]

10. Repeat step 2-8 for buffer solutions, with different pH values.
11. Plot a graph of the rate of enzyme reaction, against pH.

Question 4

What could possibly be done wrong in this investigation?

Answer 4

Intervals between testing maybe too long, to accurately find the time taken, for starch to be completely broken down.

Question 5

Potential hazards in this practical

Answer 5

• Use of hot water
• Hair must be tired back, and goggle worn, if using Bunsen burner