7.2. Transport mechanisms
A subsection of Biology, 9700, through 7. Transport in plants
Listing 10 of 310 questions
Thale cress, Arabidopsis thaliana, is used to study the roles of genes and proteins in plants. The cell membranes of the root hairs of A. thaliana contain proteins called aquaporins that allow the movement of water between the soil and the cytoplasm as shown in . cell wall soil cytoplasm aquaporin water molecule With reference to : explain how water is absorbed by root hairs of A. thaliana state why aquaporins are necessary in cell surface membranes. Describe the pathway taken by water from the cytoplasm of the root hair cell to a xylem vessel in the centre of the root. An investigation was carried out to find the effect of an enzyme in A. thaliana on the composition of the cuticle. The enzyme is involved in the production of lipid that accumulates in the cuticle. Plants were discovered with a mutation of the gene that codes for the enzyme. Some of these mutant plants (Group A) were grown in pots and their rate of transpiration was determined over three days. They were compared with control plants (Group B) in which the gene was switched on and the enzyme present. The results are shown in . 12.00 00.00 rate of transpiration / g h–1 g dry mass–1 12.00 00.00 time / hours 12.00 00.00 dark dark dark light light A B Key: mutant plants (A) control plants (B) With reference to , explain: why the rate of transpiration is higher during the day than at night in both groups of plants how the results show that the cuticle is less effective in the mutant plants.
9700_w12_qp_21
THEORY
2012
Paper 2, Variant 1
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Questions Discovered
310