# Explain how the structure of the xylem and phloem vessels are each adapted to carry out their functions in the transport system of a plant.

> WJEC A-Level Biology (Wales) — 2.1 Classification and biodiversity · Explain · 5 marks

## Mark scheme (5 marks)

1. Xylem is made from hollowed-out dead cells / has no living cell contents
2. The ends of xylem cells are removed to form a continuous tube, allowing water to pass through freely
3. Xylem cell walls are impermeable to water / strengthened with lignin, preventing water loss from the vessel
4. Phloem is made of living cells (sieve tubes) which are connected via their cytoplasm, allowing sugars to move between cells
5. Companion cells provide energy (from respiration) to aid the active transport of sugars in the phloem

## Key terms

- [xylem](https://www.gradenine.co.uk/glossary/xylem)
- [phloem](https://www.gradenine.co.uk/glossary/phloem)

## Related

- [Revision notes for WJEC A-Level Biology (Wales)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-structure-of-the-b38974ed) · Published by Druglandscape Ltd.