AQA GCSE Combined Science: Trilogy Biology Paper 1 (Foundation), 2024: Question 6

✅ Correct answers

• Less sugar is needed because fructose is sweeter.
• Cheaper to produce or buy the drink.
• Less energy / fewer calories in the drink.

Exam tip: Any two valid reasons score full marks.

💡 Key knowledge

• Fructose is sweeter than glucose, so manufacturers can use less of it.
• Using less sugar can reduce cost.
• Less sugar means less energy in the drink.

🧠 Exam technique

• Give two separate reasons.
• Keep each reason short and specific.
• If you say “cheaper,” link it to why: less sugar needed or cheaper to produce.

❌ Common errors

• Repeating the idea of sweetness — the question says do not refer to sweetness.
• Saying only “it is better” without explaining why.
• Writing one reason twice in different words.

✅ Correct answer

Test: Add Benedict’s reagent to the drink and heat it.

Colour of positive result: green, yellow, orange, brown or brick red (any of these).

💡 Key knowledge

• Benedict’s test is used for reducing sugars.
• The mixture must be heated for the test to work properly.
• A positive result changes from blue to a range of warm colours.

🧠 Exam technique

• Always name the reagent.
• Always include the heating step.
• Then give the positive colour.

❌ Common errors

• Saying “warm it” instead of clearly stating heat can lose the method mark if too vague.
• Using iodine test colours — iodine is for starch, not sugar.
• Forgetting to mention a positive colour.

✅ Correct answer

Test: Add Biuret reagent.

Colour of positive result: mauve / purple / lilac / pink-purple.

💡 Key knowledge

• Biuret test is for protein.
• Positive result is a purple / lilac colour change.

🧠 Exam technique

• One mark for the test, one mark for the colour.
• You can also say Biuret A and Biuret B, or sodium hydroxide + copper sulfate if asked in that way.

❌ Common errors

• Writing Benedict’s test instead of Biuret.
• Giving the wrong colour, such as blue-black.
• Forgetting the colour altogether.

✅ Full-mark answer

Protein digestion: Protease enzymes break protein down into amino acids. Protease is produced in the stomach, pancreas, and small intestine. In the stomach, hydrochloric acid provides the correct acidic pH for protease to work.

Fat digestion: Lipase breaks fat down into fatty acids and glycerol. Lipase is produced by the pancreas and small intestine. Bile is produced by the liver and released from the gall bladder. Bile emulsifies fat into small droplets, giving a larger surface area for lipase, and neutralises acid so enzymes work at the correct pH.

💡 Key knowledge

• Protein → amino acids by protease.
• Fat → fatty acids + glycerol by lipase.
• Bile does not digest fat itself; it helps by emulsifying it.
• Protease and lipase are made in the pancreas and small intestine; protease also works in the stomach.

🧠 Exam technique

• To reach the top level, you must describe both protein and fat.
• Include:
  • the enzyme name
  • what it breaks down into
  • where it is produced
• Try to link each enzyme to its job: “protease digests protein”, “lipase digests fat”.

❌ Common errors

• Saying fat is broken down by protease.
• Missing the products: amino acids, fatty acids and glycerol.
• Forgetting where enzymes are made.
• Thinking bile is an enzyme — it is not an enzyme.
• Only describing one nutrient. The mark scheme says top-level answers must cover protein and fat.

Food tests

• Sugar: Benedict’s + heat → green/yellow/orange/brown/brick red
• Protein: Biuret → mauve/purple/lilac

Digestion facts

• Protein → amino acids
• Fat → fatty acids + glycerol
• Protease digests protein
• Lipase digests fat
• Bile emulsifies fat