2025 A Level Biology A H420/03 Unified biology (Verified Question Paper With Mark Scheme Combined June 2025)

Wednesday 18 June 2025 – Morning A Level Biology A H420/03 Unified biology Time allowed: 1 hour 30 minutes (Verified Question Paper With Mark Scheme Combined June 2025) 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 2025 [601/4260/1] DC (WW/CB) 345392/5 OCR is an exempt Charity Turn over 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] (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. 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] (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. .......................................................................................................................................................... ..........................................................................................................................................................