Some fruits contain protease enzymes. These enzymes can denature the proteins in milk, causing the milk to clot. You will investigate the effect of protease concentration on the time taken for milk to clot. You will use your results to estimate the concentration of protease in a fruit extract. You are provided with the materials shown in Table 1.1. Table 1.1 labelled | contents | hazard | volume/cm³ --- | --- | --- | --- P | 100% protease solution | none | 50 M | milk | none | 30 W | distilled water | none | 100 U | fruit extract containing unknown protease concentration | none | 20 If any solution comes into contact with your skin, wash off immediately under cold water. It is recommended that you wear suitable eye protection. You will need to make different concentrations of protease solution, using proportional dilution of the 100% protease solution, P. You will need to prepare 10cm³ of each concentration, using P and W. Table 1.2 shows how to prepare one of the concentrations of protease you will use. Decide which other concentrations of protease you will use. Carry out step 1 to step 8. step 1 Stir the 100% protease solution, P. In the beakers provided, prepare the concentrations of protease as shown in Table 1.2. step 2 Label test-tubes with the concentrations of protease stated in Table 1.2. step 3 Put 2 cm³ of milk, M, into each labelled test-tube. step 4 Put 1 cm³ of the 100% protease solution, P, into the appropriately labelled test-tube. Start timing. step 5 Hold the test-tube at an angle and slowly rotate the test-tube as shown in [Figure 1.1]. Hold a piece of black card behind the test-tube and observe the thin layer of milk on the side of the test-tube. step 6 As soon as a number of small clots appear, stop timing and record the value in (a)(ii). If there are no clots after 180 seconds, stop timing and record as 'more than 180'. milk drains back smoothly from the sides of the test-tube small clots stick to the sides of the test-tube no clotting clotting [Figure 1.1] step 7 Repeat step 4 to step 6 with each of the other concentrations of protease you prepared in step 1. Record your results in (a)(ii). step 8 Repeat step 2 to step 7 using clean test-tubes.