AQA GCSE Biology Biology Paper 1 (Foundation), June 2025: Question 7

✅ Correct Answers (Any one)

• Type 2 diabetes (best answer)
• Coronary heart disease (CHD) / Cardiovascular disease (CVD)
• High blood pressure
• Heart attack
• Stroke
• Osteoarthritis / arthritis
• Certain cancers (e.g. bowel, breast)
• Liver disease / sleep apnoea

❌ Common Errors & Lost Marks

• Writing just "diabetes" without stating Type 2 (ignored by examiners).
• Stating Type 1 diabetes (an autoimmune disorder, not caused by obesity).
• Stating "high cholesterol" or "heart failure" (these are not credited).

✅ Requirements for Full Marks (4/4)

1. y-axis Label & Scale [1 mark]:
   • Label: Mean obesity rate in arbitrary units
   • Scale: Linear, starting at 0, going up in equal steps (e.g., 5, 10, 15, 20, 25, 30, 35) taking up more than half the grid.
2. Plotting Points [2 marks]:
   • All 5 points plotted correctly to within ±½ small square:
   C: (172, 25) | D: (150, 23) | E: (110, 15) | F: (144, 19) | G: (192, 32)
   (3 or 4 points plotted correctly scores 1 mark).
3. Line of Best Fit [1 mark]:
   • A single straight line drawn with a ruler passing evenly through or between the points.

🧠 Exam Technique for Graph Drawing

• Copy the table header exactly: Write the entire text from the column header for the axis label.
• Use sharp pencil & neat 'x' marks: Large blobs can exceed the ±½ small square tolerance.
• Line of best fit: Never join dots dot-to-dot with jagged segments unless asked. Balance points evenly above and below the line.

✅ Correct Answers

07.3: Scatter graph (or scattergram / scatter diagram) [1 mark]

07.4: ☑ Positive correlation [1 mark]

💡 Key Knowledge: Interpreting Scatter Graphs

• Positive correlation: As variable X increases, variable Y increases (dots trend from bottom-left to top-right).
• Inversely proportional: As X doubles, Y halves (a specific curved relationship, not a straight upward trend).
• No correlation: Points are scattered randomly with no clear trendline.

✅ Model Answer [4 marks]

At 30 °C:

• Observation explanation: Starch is no longer present / has been broken down [1 mark].
• Enzyme activity: The enzyme (amylase) is active / working close to its optimum temperature, breaking starch into sugars [1 mark].

At 90 °C:

• Observation explanation: Starch is still present [1 mark].
• Enzyme state: The enzyme (amylase) has denatured (active site shape has changed), so it cannot bind or break down starch [1 mark].

❌ Common Misconceptions to Avoid

• Never write "enzymes are killed": Enzymes are proteins/molecules, not living organisms. The mark scheme explicitly states: "do NOT accept amylase / enzyme has been killed". Always write denatured.
• Missing the indicator link: Iodine stays yellow-brown when starch is absent, but turns blue-black when starch is present. Clearly state whether starch is present or absent in each explanation.

💡 Lock-and-Key Mechanism at High Temperatures

At 90 °C, high thermal energy breaks the bonds holding the enzyme's 3D tertiary structure together. The active site changes shape, meaning the starch substrate is no longer complementary and cannot fit to form enzyme-substrate complexes.

✅ Correct Answer

☑ Test more temperatures between 10 °C and 60 °C.

🧠 Exam Technique: Locating the Optimum

Table 6 shows amylase worked at 30 °C (iodine remained yellow-brown), but starch was not fully broken down at 10 °C or 60 °C (blue-black). The true optimum temperature must lie somewhere between the highest and lowest temperatures where activity changed: between 10 °C and 60 °C. Testing smaller temperature intervals in this range narrows down the peak rate.

💡 Site of Production vs. Site of Action

Pay close attention to what the question asks! It asks for the organ where the enzyme is active, not where it is produced. Trypsin is produced by the pancreas, but it is secreted into and active in the small intestine.