EDEXCEL A-LEVEL BIOLOGY
Biology
A-Level Questions
Students Struggle With Most
& How to Answer Them
Full model answers · Examiner tips · Mark scheme breakdowns
30 8 50+ 100%
Pages Topics Questions Exam Board
For personal revision use · Year 12 & 13 · Edexcel Specification
,Edexcel A-Level Biology | Questions & Answers Guide 2
Contents
# Topic Page
1 Biological Molecules 4
2 Cells & Microscopy 7
3 Enzymes 10
4 Cell Transport & Membranes 13
5 DNA, Genetics & Inheritance 16
6 Respiration & Photosynthesis 19
7 Evolution, Biodiversity & Classification 23
8 Ecology, Populations & Ecosystems 26
— Revision Checklist 29
— Top Mistakes & How to Fix Them 30
This guide zeroes in on the questions that consistently trip up Edexcel A-Level Biology students.
Every question here is paired with a full model answer — the kind of answer that earns all the
marks — plus a focused examiner tip telling you exactly what the mark scheme rewards. Read
each question, attempt it yourself, then check your answer against the model. Use the checklist at
the back to track your progress.
Edexcel A-Level Biology Revision Guide Know It · Explain It · Ace It
, Edexcel A-Level Biology | Questions & Answers Guide 3
CHAPTER 1
Biological Molecules
Students lose marks here by being too vague. 'It stores energy' is not enough. You need to link
specific molecular features to specific functions.
Key Terms
Monomer A small unit that bonds with others to form a larger polymer molecule.
Polymer A large molecule built from many monomers joined by condensation reactions.
Condensation A reaction that joins two molecules by removing a water molecule, forming a covalent
bond.
Hydrolysis A reaction that breaks a covalent bond by adding water.
Reducing sugar A sugar that can donate electrons to reduce another compound — detected by
Benedict's test.
Phosphodiester bond The covalent bond linking nucleotides in a DNA or RNA strand (between sugar and
phosphate groups).
Hydrogen bond A weak electrostatic attraction between a slightly positive hydrogen atom and a
slightly negative atom (O or N).
Questions & Model Answers
Explain why cellulose is suitable for its role as a structural component of plant
Q1 [4 marks]
cell walls.
✔ MODEL Cellulose is made of beta-glucose monomers joined by 1,4-glycosidic bonds. Because
ANSWER alternate beta-glucose molecules are rotated 180°, the chains are straight rather than
coiled. Straight chains can run parallel and form hydrogen bonds between adjacent
chains, bundling into strong microfibrils. These microfibrils give the cell wall high
tensile strength, preventing the cell from bursting under internal water pressure
(turgor). The many hydrogen bonds collectively provide rigidity despite each individual
bond being weak.
★ EXAMINER Mention: beta-glucose → straight chains → hydrogen bonds between chains → microfibrils →
TIP tensile strength. Each of those steps is typically a separate mark point.
Describe how you would test for the presence of a non-reducing sugar in a
Q2 [4 marks]
food sample.
Edexcel A-Level Biology Revision Guide Know It · Explain It · Ace It
Biology
A-Level Questions
Students Struggle With Most
& How to Answer Them
Full model answers · Examiner tips · Mark scheme breakdowns
30 8 50+ 100%
Pages Topics Questions Exam Board
For personal revision use · Year 12 & 13 · Edexcel Specification
,Edexcel A-Level Biology | Questions & Answers Guide 2
Contents
# Topic Page
1 Biological Molecules 4
2 Cells & Microscopy 7
3 Enzymes 10
4 Cell Transport & Membranes 13
5 DNA, Genetics & Inheritance 16
6 Respiration & Photosynthesis 19
7 Evolution, Biodiversity & Classification 23
8 Ecology, Populations & Ecosystems 26
— Revision Checklist 29
— Top Mistakes & How to Fix Them 30
This guide zeroes in on the questions that consistently trip up Edexcel A-Level Biology students.
Every question here is paired with a full model answer — the kind of answer that earns all the
marks — plus a focused examiner tip telling you exactly what the mark scheme rewards. Read
each question, attempt it yourself, then check your answer against the model. Use the checklist at
the back to track your progress.
Edexcel A-Level Biology Revision Guide Know It · Explain It · Ace It
, Edexcel A-Level Biology | Questions & Answers Guide 3
CHAPTER 1
Biological Molecules
Students lose marks here by being too vague. 'It stores energy' is not enough. You need to link
specific molecular features to specific functions.
Key Terms
Monomer A small unit that bonds with others to form a larger polymer molecule.
Polymer A large molecule built from many monomers joined by condensation reactions.
Condensation A reaction that joins two molecules by removing a water molecule, forming a covalent
bond.
Hydrolysis A reaction that breaks a covalent bond by adding water.
Reducing sugar A sugar that can donate electrons to reduce another compound — detected by
Benedict's test.
Phosphodiester bond The covalent bond linking nucleotides in a DNA or RNA strand (between sugar and
phosphate groups).
Hydrogen bond A weak electrostatic attraction between a slightly positive hydrogen atom and a
slightly negative atom (O or N).
Questions & Model Answers
Explain why cellulose is suitable for its role as a structural component of plant
Q1 [4 marks]
cell walls.
✔ MODEL Cellulose is made of beta-glucose monomers joined by 1,4-glycosidic bonds. Because
ANSWER alternate beta-glucose molecules are rotated 180°, the chains are straight rather than
coiled. Straight chains can run parallel and form hydrogen bonds between adjacent
chains, bundling into strong microfibrils. These microfibrils give the cell wall high
tensile strength, preventing the cell from bursting under internal water pressure
(turgor). The many hydrogen bonds collectively provide rigidity despite each individual
bond being weak.
★ EXAMINER Mention: beta-glucose → straight chains → hydrogen bonds between chains → microfibrils →
TIP tensile strength. Each of those steps is typically a separate mark point.
Describe how you would test for the presence of a non-reducing sugar in a
Q2 [4 marks]
food sample.
Edexcel A-Level Biology Revision Guide Know It · Explain It · Ace It
