1 The statements in the table below refer to three polysaccharide molecules. Complete the table. If the statement is correct, place a tick ( ) in the box and if the statement is incorrect place a cross ( ) in the box. Statement Starch Cellulose Glycogen glycosidic bonds present polymer of α-glucose unbranched chains only only found in plants 2 Figure 1 shows the structure of a molecule of lactose. (4 marks) Figure 1 a Draw a diagram to show the monosaccharides formed when lactose is hydrolysed. b Name the enzyme which catalyses the hydrolysis of lactose. c Lactose is a reducing sugar. Describe how you would test a liquid to show it contained reducing sugar. (3 marks) This resource sheet may have been changed from the original 1
3 Amylase is an enzyme. It catalyses the breakdown of starch to maltose. Students mixed a starch solution with amylase. The concentration of amylase and the concentration of starch were controlled. They recorded the concentration of maltose at intervals for 30 minutes. Figure 2 shows their results. Figure 2 a Suggest two other factors the students would have controlled. b Describe how the concentration of maltose changed over the period shown in Figure 2. c i A tangent has been drawn to the curve in Figure 2. Explain how you could use this line to calculate the initial rate of reaction. ii The rate of reaction was lower after 10 minutes than it was at the start. Explain why. This resource sheet may have been changed from the original 2
4 a Describe how you could carry out the emulsion test to show that olives contain lipids. (3 marks) Figure 3 shows the structure of a phospholipid molecule. Figure 3 b i Name the parts of the molecule labelled X and Y. X Y. ii Z is a fatty acid. Fatty acids can be saturated or unsaturated. Describe the difference between a saturated fatty acid and an unsaturated fatty acid. c Describe how a phospholipid molecule differs in structure from a triglyceride molecule. This resource sheet may have been changed from the original 3
5 Figure 4 shows a molecule of a protein called lactalbumin. Figure 4 a Give the name of the chemical group found at A. b Lactalbumin has a tertiary structure. Using evidence from the diagram, describe the tertiary structure of a protein. c Lactalbumin does not have a quaternary structure. Use the diagram to explain why. d Lactalbumin is not a conjugated protein. Use the diagram to explain why. 6 A student carried out an investigation using salivary amylase. Six wells (holes) of the same size were cut in a starch agar plate. Each well was filled with the same concentration and volume of amylase solution. An equal volume of buffer solution was added to produce a different ph in each well. The plates were incubated at 25 C for 24 hours and then covered with iodine solution. The iodine turned the starch blue-black. It was observed that there were clear rings around some wells. The width of these clear rings is shown in the table. This resource sheet may have been changed from the original 4
ph Width of clear ring / mm 1 0 3 2 5 6 7 11 9 5 11 0 a There are clear rings around some of the wells. Explain why. b Calculate the rate of reaction at ph 7. Show your working. c The student concluded that the optimum ph for amylase activity was ph 7. This conclusion may not be valid. Explain why. This resource sheet may have been changed from the original 5
d Use your knowledge of enzyme structure to explain the result obtained at ph 11. (3 marks) e Describe a control experiment for this investigation. This resource sheet may have been changed from the original 6