AQA GCSE Biology Biology Paper 1 (Foundation), June 2024: Question 5

✅ Correct Answers

05.1: Tick two boxes:

• Ionising radiation [1 mark]
• Viruses [1 mark]

05.2: Tick one box:

• Mitosis [1 mark]

💡 Key Knowledge

• Cancer is uncontrolled cell growth and division forming a tumour.
• Carcinogens (cancer-causing agents) include ionising radiation (e.g. UV rays, X-rays) and certain viruses (e.g. HPV causes cervical cancer).
• Cancerous human body cells divide by mitosis. Binary fission is cell division in prokaryotes (bacteria), and fertilisation is the fusion of gametes.

❌ Common Errors

• Selecting Salmonella: while bacteria cause disease, they do not directly trigger cancer.
• Selecting Antibiotics: these kill bacteria, they do not cause cancer.
• Ticking only one box for 05.1 despite the question explicitly requiring two.

✅ Correct Answers

05.3 [2 marks]:

• "Before a cell divides, the cell needs to grow." [1 mark]
• "Before a cell divides, the DNA in the nucleus needs to replicate." [1 mark]

05.4 [1 mark]: Tick 40%

05.5 [1 mark]: Tick Chromosomes are pulled to each end of the cell.

💡 Cell Cycle Stages

• Stage 1 (Interphase): The cell increases in size and sub-cellular structures (e.g., mitochondria, ribosomes) multiply, then DNA replicates to form two copies of each chromosome.
• Stage 2 (Mitosis / Stage X): One set of chromosomes is pulled to each end of the cell and the nucleus divides.
• Stage 3 (Cytokinesis): The cytoplasm and cell membranes divide to form two identical cells.

🧠 Exam Technique: Reading the Pie Chart

In Figure 4, the circle is marked with tick marks dividing it into equal 10% tenths (10 segments total).

• Count the segments spanned by the "Cell growth stage": it covers 4 sections out of 10.
• 4 / 10 = 40% .
• Stage X represents active mitosis (nuclear division), so chromosomes are being pulled apart.

✅ Correct Answers

05.6 [1 mark]: (cell) membrane

05.7 [3 marks]: 62.5 µm

📐 Step-by-Step Calculation

Step 1: Use the magnification equation

Real size = Image size / Magnification

Real size = 50 mm / 800 [1 mark]

Step 2: Calculate the real size in mm

50 / 800 = 0.0625 mm [1 mark]

Step 3: Convert mm to micrometres (µm)

Since 1 mm = 1000 µm, multiply by 1000:

0.0625 × 1000 = 62.5 µm [1 mark]

❌ Common Errors

• 05.6: Calling Z the "cell wall". Animal cells do not have a cell wall.
• 05.7: Forgetting to convert units and leaving the answer as 0.0625 .
• Dividing by 1000 instead of multiplying when converting mm to µm.

✅ Correct Answers

05.8 [2 marks]:

• "Preclinical testing of cancer drugs is done using cells." [1 mark]
• "To check if the drug is safe, the drug is tested on people." [1 mark]

05.9 [1 mark]: placebo

💡 Drug Testing Stages

• Preclinical trials: Done in the lab on human cells and tissues, followed by live animals to test for toxicity and efficacy.
• Clinical trials: Tested on healthy human volunteers (people) at very low doses to check for safety and side effects, then on patients to find the optimum dose.
• Placebo: An inactive substance (e.g. sugar pill) identical in appearance to the drug, used as a control to eliminate psychological bias.

🧠 Exam Tip

Notice the box options in 05.8: cells, people, plants, viruses. Carefully link "preclinical" to isolated biological systems (cells) and "checking safety in patients/volunteers" to people.