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ggfWednesday 18 June 2025 – Morningfgfgfgfgfgfgfgfgfgfgfgfgfgfgfg
uyuA Level Biology A A-Level OCR 2025 Biology A Paper 3
6t6uH420/03 Unified biology
gfgTime allowed: 1 hour 30 minutes
, 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
Hfgdf dfdfgdhg djdhjhg ddgjhdj gjdkg ddjaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
aaaaaaaaaaaaaaaaaaaaaaaaaa
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
ggfWednesday 18 June 2025 – Morningfgfgfgfgfgfgfgfgfgfgfgfgfgfgfg
uyuA Level Biology A A-Level OCR 2025 Biology A Paper 3
6t6uH420/03 Unified biology
gfgTime allowed: 1 hour 30 minutes
, 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
