Oxford Cambridge and RSA
Wednesday 18 June 2025 – Morning
A Level Biology A
H420/03 Unified biology
Time allowed: 1 hour 30 minutes
You can use:
• a scientific or graphical calculator
• a ruler (cm/mm)
Please write clearly in black ink. Do not write in the barcodes.
Centre number Candidate number
First name(s)
Last name
INSTRUCTIONS
• Use black ink. You can use an HB pencil, but only for graphs and diagrams.
• Write your answer to each question in the space provided. If you need extra space use the lined
pages at the end of this booklet. The question numbers must be clearly shown.
• Answer all the questions.
• Where appropriate, your answer should be supported with working. Marks might be given
for using a correct method, even if your answer is wrong.
INFORMATION
• The total mark for this paper is 70.
• The marks for each question are shown in brackets [ ].
• Quality of extended response will be assessed in questions marked with an asterisk (*).
• This document has 28 pages.
ADVICE
• Read each question carefully before you start your answer
OCR A Level Biology A H420/03 Unified biology Question paper &
Marking Scheme SUMMER 2025
, 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 10µm
• a length of 800µm.
(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 = πr2l
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
Wednesday 18 June 2025 – Morning
A Level Biology A
H420/03 Unified biology
Time allowed: 1 hour 30 minutes
You can use:
• a scientific or graphical calculator
• a ruler (cm/mm)
Please write clearly in black ink. Do not write in the barcodes.
Centre number Candidate number
First name(s)
Last name
INSTRUCTIONS
• Use black ink. You can use an HB pencil, but only for graphs and diagrams.
• Write your answer to each question in the space provided. If you need extra space use the lined
pages at the end of this booklet. The question numbers must be clearly shown.
• Answer all the questions.
• Where appropriate, your answer should be supported with working. Marks might be given
for using a correct method, even if your answer is wrong.
INFORMATION
• The total mark for this paper is 70.
• The marks for each question are shown in brackets [ ].
• Quality of extended response will be assessed in questions marked with an asterisk (*).
• This document has 28 pages.
ADVICE
• Read each question carefully before you start your answer
OCR A Level Biology A H420/03 Unified biology Question paper &
Marking Scheme SUMMER 2025
, 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 10µm
• a length of 800µm.
(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 = πr2l
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
