AQA GCSE Biology Biology Paper 1 (Higher), June 2025: Question 2

✅ Acceptable Answers (Any one)

• Type 2 diabetes (best answer)
• Coronary heart disease (CHD) / heart disease / cardiovascular disease (CVD)
• High blood pressure (hypertension)
• Stroke
• Heart attack
• Osteoarthritis / arthritis
• Cancer (certain types)
• Liver disease / sleep apnoea

❌ Common Errors & What Is Rejected

• Writing just "diabetes" unqualified (NEVER give just "diabetes" – AQA specifies you must identify Type 2).
• Writing Type 1 diabetes (this is an autoimmune condition, not caused by lifestyle/obesity).
• High cholesterol or heart failure (ignored by the mark scheme).

💡 Data to Plot from Table 1

Points A (122, 18) and B (80, 9) are already done for you.

• C: x = 172, y = 25
• D: x = 150, y = 23
• E: x = 110, y = 15
• F: x = 144, y = 19
• G: x = 192, y = 32

🧠 Exam Technique: Step-by-Step Plotting

1. y-axis label: Must match Table 1 header exactly: Mean obesity rate in arbitrary units .
2. y-axis scale: Must be linear, starting at 0, reaching at least 32, using sensible intervals (e.g., 5 or 10 units per large grid block).
3. Plotting points: Use a sharp pencil and neat small crosses ( × ). You are allowed a tolerance of ±½ a small square.
4. Line of best fit: Use a transparent ruler. Draw a single straight line through the balance of points. Do not join point-to-point.

✅ Correct Responses

02.3: Type of graph [1 mark]

scatter graph / scatter diagram / scattergram

02.4: Relationship shown [1 mark]

☑ Positive correlation

💡 Scientific Reasoning

• Scatter graph: Used when displaying two continuous variables to see if there is an association or correlation between them.
• Positive correlation: As one variable increases (mean sugar intake per person per day), the other variable also increases (mean number of decayed teeth).

✅ Full Mark Model Response (4 marks)

At 30 °C:

• Observation: Iodine solution remains yellow-brown because starch is not present / has been broken down [1 mark].
• Explanation: Because the amylase / enzyme is active / working and digested the starch into sugars [1 mark].

At 90 °C:

• Observation: Iodine solution turns blue-black because starch is still present / has not been broken down [1 mark].
• Explanation: Because the high temperature caused the amylase / enzyme to denature (active site changed shape) [1 mark].

❌ Critical Scientific Vocabulary Warnings

• NEVER say "enzymes are killed" or "enzymes die": Enzymes are biological catalysts (proteins), not living organisms. You will lose the denaturation mark.
• Identify what iodine tests for: Iodine tests for starch, not amylase. Starch present = blue-black; starch absent = yellow-brown.
• Always link result to cause: Don't just say "it's denatured" without stating that starch was therefore not broken down.

✅ Correct Answer

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

🧠 Exam Technique: Reading the Evidence

Looking at Table 2:

• At 10 °C: Iodine was blue-black (starch not broken down in 5 mins).
• At 30 °C: Iodine was yellow-brown (starch broken down).
• At 60 °C: Iodine was blue-black (amylase inactive or denatured).

Amylase only worked completely within the range surrounding 30 °C. Therefore, the true optimum must lie somewhere between 10 °C and 60 °C. Testing narrower intervals (e.g. 20 °C, 35 °C, 40 °C, 50 °C) in this specific window allows you to find the exact optimum.

💡 Key Digestive Knowledge

• Pepsin in the Stomach: The stomach produces hydrochloric acid (HCl), providing a low pH of around 1.5–2, which is the optimum pH for pepsin to break down proteins into amino acids.
• Trypsin in the Small Intestine: Bile (made in the liver, stored in the gall bladder) neutralises stomach acid and emulsifies fats, creating an alkaline pH (around 7–8) suited to trypsin.

❌ Common Misconceptions

• Do not confuse where an enzyme is made with where it is active. Trypsin is made in the pancreas, but it is released into and active inside the small intestine.
• Writing "mouth" for pepsin: Saliva contains amylase (neutral pH), not protease.