CAIE A Level Biology 9700 · Biological molecules
A student investigates the effect of placing plant cells in a concentrated salt solution. The cells lose water and their cytoplasm shrinks, but the cell walls do not collapse. Instead, the cell walls retain their shape and resist the inward pull from the shrinking protoplast.
Explain how the structure of cellulose and its arrangement in plant cell walls enable them to withstand high internal pressures and resist deformation.
6 marks, so the mark scheme is looking for about 6 separate creditworthy points. Making the same point twice in different words earns it once.
Explain means: Give the reasons or the mechanism: why or how something happens. Link each point to the next with because, so or which means. A list of facts with no links usually loses the reasoning marks.
Written by Markquill to follow the Cambridge International syllabus. Markquill is independent and is not affiliated with or endorsed by Cambridge International.