GCSE BIOLOGY • SPECIFICATION 1.1

Cell Biology

Aligned primarily to AQA GCSE Biology (8461/8464) and major UK exam boards.

Mastering command terms and mark-scheme precision.

1. Prokaryotic vs Eukaryotic Cells

Exam Definition (Learn this word-for-word):

"Prokaryotic cells are smaller than eukaryotic cells. They have cytoplasm, a cell membrane, and a cell wall. Their genetic material is NOT enclosed within a nucleus."

Rapid Recall: Command Term Drill

Name the organelle responsible for protein synthesis.

Ribosomes

State the function of the mitochondria.

Release energy through aerobic respiration.

2. Microscopy & Significant Figures
Magnification Formula: $\text{Magnification} = \frac{\text{Image Size}}{\text{Actual Size}}$

⚠️ The Precision Rule

Always give your answer to the appropriate number of significant figures shown in the data provided in the question. Rounding errors = 0 marks.

ConversionMethod
cm $\rightarrow$ mm$\times 10$
mm $\rightarrow$ $\mu m$$\times 1000$
$\mu m$ $\rightarrow$ nm$\times 1000$

Q: Describe the difference between resolution and magnification.

Magnification is how many times bigger the image is than the object. Resolution is the ability to distinguish between two separate points (the level of detail).

3. Transport: Osmosis & Active Transport

Mark-Scheme Osmosis:

"The net movement of water from a dilute solution to a concentrated solution through a partially permeable membrane."

Note: You can use "high water potential to low water potential", but do NOT mix both terminologies in one sentence.

[Image showing water molecules moving through a partially permeable membrane]

Explain how mineral ions are absorbed by root hair cells (3 Marks).

  1. Absorbed by Active Transport.
  2. Movement from low concentration (soil) to high concentration (cell) / against the gradient.
  3. This requires energy from respiration.
4. Stem Cells (6-Mark Evaluation Framework)

Scaffold: Evaluation Questions

Use this structure for coherence:

  • Para 1: Advantages (e.g., Can treat paralysis/diabetes; clones are not rejected).
  • Para 2: Ethical Disadvantages (e.g., Embryos have potential to develop into a human; some religious groups believe life begins at conception).
  • Para 3: Risks/Other (e.g., Potential for transfer of viral infections).
  • Para 4: Justified Conclusion (Summarise based on evidence).
5. Required Practical: Microscopy (The "Why" Factor)

Method questions often shift to "Explanations". Know the reason for every step.

Action Reasoning (The "Why")
Use Iodine solution To stain sub-cellular structures (like the nucleus) to make them visible.
Lower coverslip at an angle To prevent air bubbles which obscure the view of the cells.
Select lowest power lens first To provide a wider field of view and make it easier to find the cells.

Final Exam Guardrail

• Never say "water concentration"; use "dilute/concentrated solution".
• Mitosis produces genetically identical cells for growth and repair.
• Ensure you mention "Energy from respiration" for every Active Transport answer.
• Check if the question asks for a "Description" (what) or "Explanation" (why).

📚 Index Topic 2: Organisation →