CAIE A Level Biology 9700 · Transport in plants
Sieve tube elements and companion cells are two distinct cell types found in the phloem of herbaceous dicotyledonous plants.
(a) Compare the structures of a sieve tube element and a companion cell. (b) Explain why a sieve tube element requires a companion cell to function effectively.
4 marks, so the mark scheme is looking for about 4 separate creditworthy points. Making the same point twice in different words earns it once.
Compare means: Give similarities or differences between two things, and say which side each point belongs to. Write each point as a pair, for example: A is X, whereas B is Y. Two separate descriptions rarely earn the marks.
Written by Markquill to follow the Cambridge International syllabus. Markquill is independent and is not affiliated with or endorsed by Cambridge International.