Yeast cells contain enzymes that hydrolyse sucrose into reducing sugars, as shown in Fig. 1.1. enzymes in yeast cells sucrose → reducing sugars Fig. 1.1 You will investigate the activity of the enzymes in yeast cells. The yeast cells will be immobilised in sodium alginate beads. You are provided with the materials shown in Table 1.1. Table 1.1 labelled contents hazard volume/cm³ Y yeast cell suspension none 30 A sodium alginate solution harmful irritant 20 C calcium chloride solution harmful irritant 30 S sucrose solution none 100 B Benedict's solution harmful irritant 30 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 investigate the activity of yeast enzymes by using different numbers of beads of immobilised yeast cells in sucrose solution, S. Carry out step 1 to step 9 to immobilise the yeast cells in sodium alginate beads. step 1 Put 10 cm³ of A into a beaker. step 2 Stir the yeast cell suspension Y with a glass rod. step 3 Put 10 cm³ of Y into the beaker containing A and mix well. step 4 Put 20 cm³ of C into another beaker. step 5 Use a 10cm³ syringe to collect 10cm³ of the mixture of A and Y. step 6 Hold this syringe over the beaker containing 20 cm³ of C (step 4), as shown in Fig. 1.2. slowly press down to release one drop at a time -plunger -barrel of syringe mixture of A and Y. calcium chloride solution, C Fig. 1.2 one drop released step 7 Hold the barrel of the syringe with one hand while slowly pressing down on the plunger with the other hand so that a drop of the mixture is released into solution C. The drop will form a bead. step 8 Repeat step 7 to make at least 31 beads. The immobilised yeast beads must be left in the beaker for 5 minutes. step 9 After 5 minutes tip the beads and the solution into a Petri dish. You will test the activity of the yeast enzymes by using different numbers of beads (1, 2, 4, 8 and 16) in sucrose solution. Carry out step 10 to step 20. step 10 Label five beakers 1, 2, 4, 8 and 16 and label five test-tubes 1, 2, 4, 8 and 16. step 11 Put 1, 2, 4, 8 or 16 beads into each of the appropriately labelled beakers, as shown in Fig. 1.3. 1 2 4 8 16 yeast bead 00 0 000 Fig. 1.3 step 12 Put 10cm³ of sucrose solution, S, into each of the beakers containing the beads. step 13 Start timing and leave for 5 minutes. While you are waiting set up a water-bath ready for step 14 and step 19. In step 19 you will use the water-bath to carry out the test for reducing sugars using Benedict's solution, B.