Biology 9700 · AS & A Level · Transport mechanisms
Transport mechanisms — practice question
Fig. 1.1 shows an electron micrograph of a transverse section through palisade mesophyll tissue from the leaf of the flowering plant Zinnia elegans.
(a)[3]
Name the structures labelled A, B and C.
(b)[2]
Calculate the width of the vacuole across line X-Y. Show your working and state your answer to the nearest micrometre ($\mu\text{m}$).
(c)[4]
The membrane around the vacuole, known as the tonoplast, has a fluid mosaic structure. Describe the structure of this membrane.
(d)[3]
Palisade mesophyll cells contain very large vacuoles. Explain how water passes from the xylem in the leaf into these vacuoles.
Worked solution & mark scheme
This 12-mark question has a full step-by-step worked solution and mark scheme. One marking point: “A = chloroplast; or, if A points to a thylakoid stack, granum / grana.” …