A LEVEL BIOLOGY A: Actual June 2025 PAST PAPER 3: Unified Biology. All Assessment
Questions & Mark Scheme [OCR H420/03]
Exam Resource Summary
The A Level Biology A June 2025 Unified Biology Paper (OCR H420/03) integrates the full official
examination paper with its detailed mark scheme to provide a focused and comprehensive revision
resource. This paper assesses students’ understanding of key biological concepts across all topic areas,
including cellular processes, genetics, physiology, ecology, and evolution, emphasizing the integration
and application of knowledge in unfamiliar contexts. By presenting each question alongside the
corresponding marking criteria, the resource offers clear guidance on analytical reasoning, practical
application, and the structured scientific argument required for high-band responses. This combined
format supports efficient revision, strengthens critical thinking and problem-solving skills, and serves as
an essential tool for preparing for the May/June 2026 OCR A Level Biology A Unified Biology
examination.
OCR is an exempt Charity
Turn over
, 2
1 The roots of plants contain a variety of cells and tissues.
(a) The photomicrograph shows a transverse section through the root of a herbaceous
dicotyledonous plant.
A
B
Name the cells labelled A and B in the photomicrograph.
A .......................................................................................................................................................
B .......................................................................................................................................................
[2]
© OCR 2025
, 3
(b) The outer surface of a root is made up of root epidermal cells.
A root hair cell is a type of root epidermal cell that has a hair‑ like extension called a root hair.
A typical root epidermal cell has a surface area to volume ratio (SA: V) of 0.3 : 1.
A root hair cell has a higher SA: V than a typical root epidermal cell.
The diagram shows a root hair cell. The diagram is not to scale.
Root hair
The root hair has:
• a diameter of 10 µm
• a length of 800 µm.
(i) Calculate the SA: V of the root hair.
Assume the root hair is cylindrical.
Use the equations:
Surface area of cylinder = 2πr(r + l )
Volume of cylinder = πr 2l
SA: V of root hair = .......................................................... [3]
(ii) State how a high SA: V helps a root hair cell perform its function.
..........................................................................................................................................................
. ................................................................................................................................................. [1]
© OCR 2025 Turn over
, 4
(c) Carbohydrates produced in palisade cells are transported in phloem to sinks, such as roots.
Describe how carbohydrates move from palisade cells into companion cells in phloem.
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
. ................................................................................................................................................. [3]
© OCR 2025
Questions & Mark Scheme [OCR H420/03]
Exam Resource Summary
The A Level Biology A June 2025 Unified Biology Paper (OCR H420/03) integrates the full official
examination paper with its detailed mark scheme to provide a focused and comprehensive revision
resource. This paper assesses students’ understanding of key biological concepts across all topic areas,
including cellular processes, genetics, physiology, ecology, and evolution, emphasizing the integration
and application of knowledge in unfamiliar contexts. By presenting each question alongside the
corresponding marking criteria, the resource offers clear guidance on analytical reasoning, practical
application, and the structured scientific argument required for high-band responses. This combined
format supports efficient revision, strengthens critical thinking and problem-solving skills, and serves as
an essential tool for preparing for the May/June 2026 OCR A Level Biology A Unified Biology
examination.
OCR is an exempt Charity
Turn over
, 2
1 The roots of plants contain a variety of cells and tissues.
(a) The photomicrograph shows a transverse section through the root of a herbaceous
dicotyledonous plant.
A
B
Name the cells labelled A and B in the photomicrograph.
A .......................................................................................................................................................
B .......................................................................................................................................................
[2]
© OCR 2025
, 3
(b) The outer surface of a root is made up of root epidermal cells.
A root hair cell is a type of root epidermal cell that has a hair‑ like extension called a root hair.
A typical root epidermal cell has a surface area to volume ratio (SA: V) of 0.3 : 1.
A root hair cell has a higher SA: V than a typical root epidermal cell.
The diagram shows a root hair cell. The diagram is not to scale.
Root hair
The root hair has:
• a diameter of 10 µm
• a length of 800 µm.
(i) Calculate the SA: V of the root hair.
Assume the root hair is cylindrical.
Use the equations:
Surface area of cylinder = 2πr(r + l )
Volume of cylinder = πr 2l
SA: V of root hair = .......................................................... [3]
(ii) State how a high SA: V helps a root hair cell perform its function.
..........................................................................................................................................................
. ................................................................................................................................................. [1]
© OCR 2025 Turn over
, 4
(c) Carbohydrates produced in palisade cells are transported in phloem to sinks, such as roots.
Describe how carbohydrates move from palisade cells into companion cells in phloem.
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
. ................................................................................................................................................. [3]
© OCR 2025
