Amylase is an enzyme found in the human body that catalyses the breakdown of starch into reducing sugars． Tea contains a chemical called tannin which affects amylase activity in the body． You are going to investigate the effect of tea on the enzyme amylase． Read all the instructions but DO NOT DO THEM until you have drawn a table for your results in the space provided in 1（a）（ii）． You should use the safety equipment provided while you are doing the practical work． Step 1 Label three test－tubes $$\(\mathbf{S 1}, \mathbf{S} 2\)$$ and $$\(\mathbf{S 3}\)$$ ． Step 2 Use a syringe to put $$\(2 \mathrm{~cm}^{3}\)$$ of starch suspension into all three test－tubes． Step 3 Label another three test－tubes A，AT and $$\(\mathbf{T}\)$$ ． Step 4 Use a clean syringe to put $$\(2 \mathrm{~cm}^{3}\)$$ of amylase solution into test－tube $$\(\mathbf{A}\)$$ and $$\(2 \mathrm{~cm}^{3}\)$$ of amylase solution into test－tube AT． Step 5 Use a clean syringe to put $$\(2 \mathrm{~cm}^{3}\)$$ of tea into test－tube AT and $$\(2 \mathrm{~cm}^{3}\)$$ of tea into test－tube $$\(\mathbf{T}\)$$ ． Step 6 Raise your hand when you are ready for hot water to be added to the beaker labelled water－bath． Step 7 Place all six test－tubes into the hot water－bath． Step 8 Use the marker pen to label three sections on a white tile，as shown in Fig．1．1． Fig． 1.1 Step 9 Add 10 drops of iodine solution to each section, as shown in Fig. 1.2. Fig. 1.2 Step 10 Start the stop-clock and pour the starch suspension in test-tube $$\(\mathbf{S} 1\)$$ into test-tube $$\(\mathbf{A}\)$$. Step 11 Use a pipette to immediately remove a drop of the mixture from test-tube $$\(\mathbf{A}\)$$ and place it onto the first drop of iodine solution in section $$\(\mathbf{A}\)$$ on the white tile. Return any mixture still in the pipette to test-tube $$\(\mathbf{A}\)$$. Step 12 Repeat step 11 every 30 seconds, until all 10 drops of iodine solution in section $$\(\mathbf{A}\)$$ have been used. Reset the stop-clock to zero. Step 13 Repeat steps 10 to 12 using test-tubes $$\(\mathbf{S 2}\)$$ and $$\(\mathbf{A T}\)$$. Step 14 Repeat steps 10 to 12 using test-tubes $$\(\mathbf{S 3}\)$$ and $$\(\mathbf{T}\)$$. For this investigation, you need to identify when all of the starch has been broken down in each test-tube. (i) Describe how you can tell if the starch has been broken down. ................................................................................................................................. (ii) Prepare a table for your results. Include in your table the time taken for starch to be broken down in all three test-tubes. If starch remained after testing with all 10 drops, record this as >300. (iii) State what can be concluded about the effect of tea on amylase activity. ....................................................................................................................................... . ....................................................................................................................................... . ................................................................................................................................. (iv) State the independent variable in this investigation. ................................................................................................................................. (v) Test-tube $$\(\mathbf{T}\)$$ did not contain amylase and was used as a control. Suggest a reason for including a control in this investigation. ....................................................................................................................................... . ....................................................................................................................................... . (vi) Explain why the test-tubes were placed in a water-bath in step 7 before the contents of the test-tubes were mixed in step 10. ....................................................................................................................................... . ....................................................................................................................................... . ................................................................................................................................. (vii) A student stated that there is an error in step 4 and step 5. Identify this error and suggest how the procedure should be improved. error ............................................................................................................................... ....................................................................................................................................... . improvement .................................................................................................................. ....................................................................................................................................... . ....................................................................................................................................... . (viii) Describe a test which would show that reducing sugars have been produced. ....................................................................................................................................... . ....................................................................................................................................... . .................................................................................................................................

Answer:

Knowledge points:

Solution: