Biology 9700/23 — May/June 2020
Cambridge AS Level · AS Level Structured Questions · worked solutions for every part, with the mark scheme
Topics Cell Membranes and Transport · Cell Structure · Transport in Plants · Infectious Diseases · Immunity · Transport in Mammals · +5 more
Water and mineral ions are transported up the stem of a plant to the leaves within xylem vessels.
Some water and mineral ions can pass out of xylem vessel elements to supply parenchyma tissue in the stem.
Fig. 1.1 is a plan diagram of a section through a stem.
Identify one location where xylem tissue occurs in the stem by drawing a label line and the letter X on Fig. 1.1.
Explain how hydrogen bonding between water molecules contributes to the movement of water within xylem vessels up the stem to the leaves.
Fig. 1.2 is a diagram of a photomicrograph showing three adjacent parenchyma cells in the stem. These parenchyma cells can be described as typical plant cells.
The arrows show the direction of movement of water between the cells.
Describe and explain the movement of water shown in Fig. 1.2.
Only some of the structures visible using the light microscope have been included in Fig. 1.2.
List the features that can be seen using the high power of a light microscope that help identify a parenchyma cell as a plant cell and not as an animal cell.
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