1. 1
   A food scientist tests a sample of a processed snack in the laboratory using iodine solution, Benedict's solution and Biuret solution to determine which nutrients it contains.

   (a)

   When iodine solution is added to a sample of the snack and it turns from browning-orange to blue-black, which nutrient does this indicate is present?

   [1 mark]

   • AProtein
   • BStarch
   • CLipid
   • DGlucose

   (b)

   Which chemical element is found in proteins but not in carbohydrates or lipids?

   [1 mark]

   • ACarbon
   • BHydrogen
   • COxygen
   • DNitrogen

   (c)

   Describe the results that would indicate a positive test for a reducing sugar, such as glucose, using Benedict's solution.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   An athlete's diet is analysed by a nutritionist. Their pasta and bread test positive for starch, their chicken breast tests positive for protein, and their olive oil tests positive for lipid content.

   (a)

   Which monomer units make up the starch found in the athlete's pasta and bread?

   [1 mark]

   • AAmino acids
   • BFatty acids and glycerol
   • CSimple sugars (glucose)
   • DNucleotides

   (b)

   Which two components combine to form the lipid molecules found in the athlete's olive oil?

   [1 mark]

   • AFatty acids and glycerol
   • BAmino acids and glucose
   • CGlucose and glycerol
   • DAmino acids and fatty acids

   (c)

   Describe the basic building blocks of the protein found in the chicken breast, and explain how they combine to form a large protein molecule.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A laboratory technician investigates how the rate of breakdown of starch by the enzyme amylase changes when the reaction is carried out at different temperatures, from 10°C up to 80°C, testing samples at regular time intervals using iodine solution.

   (a)

   Explain why the rate of starch breakdown by amylase increased as the temperature rose from 10°C towards the optimum temperature, then decreased sharply above this temperature.

   [3 marks]

   (b)

   Describe how the technician could adapt this method to investigate the effect of pH, rather than temperature, on the rate of amylase activity, and explain what results would be expected.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A biochemist studies a rare genetic condition in which a patient's digestive enzyme, lactase, does not function correctly, leading to lactose intolerance. The biochemist investigates the enzyme's structure and how a mutation to its gene affects its activity.

   (a)

   Using the lock-and-key model, explain how enzymes work as biological catalysts, and why a change in temperature or pH affects their function.

   [6 marks]

   (b)

   Explain how a mutation affecting the structure of the lactase enzyme could result in lactose intolerance, and describe how a food scientist could test whether a food sample contains lactose.

   [6 marks]

   Total for question 4: 12 marks

End of questions