Transport mechanisms: past paper questions
Real questions on transport mechanisms
The newest 20 of 22 written questions. Open one to see it on the real paper.
- 9700/22 · October/November 2023 · Q6b[2]
Explain how tension is created in the xylem vessels.
See it on the paper → - 9700/22 · October/November 2023 · Q6c(i)[2]
The walls of the cells forming the xylem vessel walls become lignified during development. Explain how this feature is important for the efficient transport of water.
See it on the paper → - 9700/22 · October/November 2023 · Q6c(ii)[1]
During the development of xylem vessels, the end walls of the cells forming the vessels break down. This contributes to minimising resistance to the flow of water. Describe one other main change that needs to occur to these cells so that their structure becomes suited to their function.
See it on the paper → - 9700/41 · October/November 2023 · Q3c(i)[2]
In 2016, a study measured the atmospheric CO 2 concentration as 400 μmol mol –1 . In the future, climate change may reduce water availability and increase atmospheric CO 2 concentrations in some habitats. Suggest how the stomatal response shown in Fig. 3.2 would allow I. pes-caprae to survive the effects of climate cha...
See it on the paper → - 9700/41 · October/November 2023 · Q3c(ii)[4]
Under certain conditions, the closure of stomata is controlled by abscisic acid. Describe how abscisic acid causes the closure of stomata.
See it on the paper → - 9700/41 · October/November 2023 · Q3d(i)[3]
Scientists investigated the effect of different concentrations of abscisic acid on root elongation in seedlings of thale cress, Arabidopsis thaliana. The seedlings were divided into four groups: a control group (0.0 μmol abscisic acid) three experimental groups, each treated with a different concentration of abscisic a...
See it on the paper → - 9700/41 · October/November 2023 · Q3d(ii)[2]
The passage outlines the role of auxin in elongation growth in plants. Complete the passage by using the most appropriate scientific terms. The binding of auxin to receptors causes to be pumped into cell walls. This activates proteins called expansins, which disrupt the links between microfibrils. The cell walls are th...
See it on the paper → - 9700/23 · May/June 2023 · Q5b(i)[4]
Describe how sucrose is transported in phloem sieve tubes from photosynthesising leaves to other parts of the plant.
See it on the paper → - 9700/22 · May/June 2022 · Q6a[3]
The source of mineral ions for the plant is the soil solution. These mineral ions are transported from the roots in the xylem. Mineral ions are also found in the phloem sap within phloem sieve tubes. Suggest why mineral ions are found within phloem sieve tubes and state how they are transported within phloem sieve tube...
See it on the paper → - 9700/22 · February/March 2022 · Q1b(iii)[1]
Name the pathway for the movement of water shown by the arrows in Fig. 1.1.
See it on the paper → - 9700/22 · February/March 2022 · Q1c[3]
Water enters the xylem vessels shown in Fig. 1.1. Explain how water moves up the xylem vessels to the leaves in a continuous column.
See it on the paper → - 9700/22 · May/June 2021 · Q2a[3]
As the young leaf matures, the quantity of sugar taken up by the leaf decreases to zero, but the need for water increases. Suggest and explain why the quantity of sugar taken up by the developing leaf decreases to zero over time, but the need for water increases.
See it on the paper → - 9700/22 · October/November 2020 · Q1a(i)[1]
Name the cell structures through which water passes from cell A to cell B without crossing their cell walls.
See it on the paper → - 9700/22 · October/November 2020 · Q1a(ii)[1]
Explain what causes water to move from cell B to cell C.
See it on the paper → - 9700/22 · October/November 2020 · Q1a(iii)[1]
Name the pathway taken by water between cell A and cell C.
See it on the paper → - 9700/22 · October/November 2020 · Q1b[4]
Most of the water that arrives at the leaf passes to the external atmosphere. With reference to Fig. 1.1, describe and explain the sequence of events occurring between point P and point Q.
See it on the paper → - 9700/23 · May/June 2019 · Q2c[3]
In the leaves of plants, both gas exchange and transpiration occur through open stomata. Suggest how the arrangement of cells in the leaf of a dicotyledonous plant contributes to the loss of water by transpiration.
See it on the paper → - 9700/23 · May/June 2019 · Q2d(ii)[2]
Suggest why the transpiration rate changed between 09:00 and 10:00.
See it on the paper → - 9700/23 · May/June 2019 · Q4a[2]
Describe two differences between the structure of a phloem sieve tube element and a xylem vessel element.
See it on the paper → - 9700/23 · May/June 2019 · Q4b[2]
Sucrose is transported in phloem sieve tubes. A student carried out a test to identify the presence of sucrose in a sample of sap taken from inside a phloem sieve tube. One of the steps in the procedure instructed the student to heat the phloem sap with hydrochloric acid. Explain why it is necessary to carry out this s...
See it on the paper →
What examiners said
Transpiration pull was frequently included in the answer for this question, and many also showed an understanding of the importance of the cohesive and adhesive forces of water. Some could have improved their description of water loss in the leaf, for example by stating that evaporation of water occurred from the surface of the spongy mesophyll cells rather than stating this was from the mesophyll...
— Examiner report, October/November 2023, 9700/22 Q6(b) (Cambridge)
There were some good answers to this question. Candidates needed to relate lignification to the concept of structure to function of xylem vessels. Reference to the waterproof nature of lignin and helping to prevent the collapse of xylem vessels were the two most common points given. Adhesion of water molecules to lignin was not credited unless it was noted that this occurred with the hydrophilic p...
— Examiner report, October/November 2023, 9700/22 Q6(c)(i) (Cambridge)
Most were able to answer this question correctly and a wide range of acceptable answers were seen.
— Examiner report, October/November 2023, 9700/22 Q6(c)(ii) (Cambridge)
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