AQA Biology A-Level
Questions Students
Struggle With Most
— And How to Answer Them —
Covering all 8 major topic areas | Full mark-scheme logic
Diagrams • Worked examples • Exam tips
For AS and A2 students targeting Grade A / A*
Detailed · Visual · Student-Friendly
,AQA Biology A-level Exam Success Guide
TABLE OF CONTENTS
# Chapter Topic Page
1 Cell Biology Cell structure, transport, division 4
2 Biological Molecules Carbs, proteins, lipids, DNA 7
3 Enzymes Kinetics, inhibition, cofactors 10
4 Exchange & Transport Gas exchange, heart, circulation 13
5 Genetics & Inheritance Meiosis, Mendel, chi-squared 16
6 Ecology Populations, energy flow, succession 19
7 Homeostasis & Control Nerves, hormones, negative feedback 22
8 Photosynthesis & RespirationCalvin cycle, ETC, oxidative phos. 25
— Exam Strategy Command words, 6-mark structure 28
— Quick-Reference Sheet Key values and equations 29
How to Use This Guide
How to use this guide: Read the question first, study the model answer, note the mark-scheme logic in orange, then
try writing your own answer before moving on.
Page 2 | AQA Biology A-level: Questions Students Struggle With Most
, AQA Biology A-level Exam Success Guide
CHAPTER 1: CELL BIOLOGY
Why Students Lose Marks Here
Cell biology questions catch students out because they use vague descriptions instead of precise
biological language. Examiners want exact structure names, correct spelling, and answers that link
structure to function. Generic phrases like "it helps the cell" score zero.
Cell Membrane — Fluid Mosaic Model
Phospholipid bilayer
Protein
Question 1 (4 marks)
Describe how the structure of a cell surface membrane allows it to control which substances enter and
leave the cell.
Common Mistake
Students often say "the membrane is selectively permeable" — this is the conclusion, not the explanation. Always
explain HOW, not just WHAT.
Model Answer:
The phospholipid bilayer forms a hydrophobic core that prevents polar molecules and ions from diffusing
freely across it (1). Channel proteins form water-filled pores that allow specific ions to pass by facilitated
diffusion (1). Carrier proteins bind to specific molecules and change shape to move them across — either
passively or actively using ATP (1). The cholesterol molecules between phospholipids reduce fluidity and
prevent small ions from leaking through (1).
Mark-scheme logic: 1 mark per distinct, accurate mechanism — not just naming a protein.
Question 2 (6 marks)
Compare and contrast mitosis and meiosis, including the significance of each process.
Page 3 | AQA Biology A-level: Questions Students Struggle With Most
Questions Students
Struggle With Most
— And How to Answer Them —
Covering all 8 major topic areas | Full mark-scheme logic
Diagrams • Worked examples • Exam tips
For AS and A2 students targeting Grade A / A*
Detailed · Visual · Student-Friendly
,AQA Biology A-level Exam Success Guide
TABLE OF CONTENTS
# Chapter Topic Page
1 Cell Biology Cell structure, transport, division 4
2 Biological Molecules Carbs, proteins, lipids, DNA 7
3 Enzymes Kinetics, inhibition, cofactors 10
4 Exchange & Transport Gas exchange, heart, circulation 13
5 Genetics & Inheritance Meiosis, Mendel, chi-squared 16
6 Ecology Populations, energy flow, succession 19
7 Homeostasis & Control Nerves, hormones, negative feedback 22
8 Photosynthesis & RespirationCalvin cycle, ETC, oxidative phos. 25
— Exam Strategy Command words, 6-mark structure 28
— Quick-Reference Sheet Key values and equations 29
How to Use This Guide
How to use this guide: Read the question first, study the model answer, note the mark-scheme logic in orange, then
try writing your own answer before moving on.
Page 2 | AQA Biology A-level: Questions Students Struggle With Most
, AQA Biology A-level Exam Success Guide
CHAPTER 1: CELL BIOLOGY
Why Students Lose Marks Here
Cell biology questions catch students out because they use vague descriptions instead of precise
biological language. Examiners want exact structure names, correct spelling, and answers that link
structure to function. Generic phrases like "it helps the cell" score zero.
Cell Membrane — Fluid Mosaic Model
Phospholipid bilayer
Protein
Question 1 (4 marks)
Describe how the structure of a cell surface membrane allows it to control which substances enter and
leave the cell.
Common Mistake
Students often say "the membrane is selectively permeable" — this is the conclusion, not the explanation. Always
explain HOW, not just WHAT.
Model Answer:
The phospholipid bilayer forms a hydrophobic core that prevents polar molecules and ions from diffusing
freely across it (1). Channel proteins form water-filled pores that allow specific ions to pass by facilitated
diffusion (1). Carrier proteins bind to specific molecules and change shape to move them across — either
passively or actively using ATP (1). The cholesterol molecules between phospholipids reduce fluidity and
prevent small ions from leaking through (1).
Mark-scheme logic: 1 mark per distinct, accurate mechanism — not just naming a protein.
Question 2 (6 marks)
Compare and contrast mitosis and meiosis, including the significance of each process.
Page 3 | AQA Biology A-level: Questions Students Struggle With Most
