Plants absorb dissolved mineral ions, such as nitrate (NO3−\text{NO}_3^-NO3−), from the soil to synthesise amino acids and nucleic acids. NRT2\text{NRT2}NRT2 is a high-affinity active transporter protein located in root cell membranes.
Scientists investigated the role of NRT2\text{NRT2}NRT2 in nitrate uptake using two types of barley (Hordeum vulgare) plants: Type W (wild-type plants with normal expression of the NRT2\text{NRT2}NRT2 gene) and Type M (mutant plants with a knock-out mutation in the NRT2\text{NRT2}NRT2 gene). To estimate the rate of nitrate uptake, the scientists placed the roots of Type W and Type M plants in a nutrient solution containing radioactively labelled nitrate (15N^{15}\text{N}15N). They measured the percentage of 15N^{15}\text{N}15N remaining in the external solution over a period of 16 hours.
The results are shown in the graph below:
Calculate the ratio of the percentage of 15N^{15}\text{N}15N remaining in the external solution of Type W to Type M plants 16 hours after providing the 15N^{15}\text{N}15N. Express your answer in the form N:1N : 1N:1, where N N\,N is rounded to two decimal places.
Practise AQA A Level Biology Transport across cell membranes with exam-style questions for A Level Biology. 11 questions covering Transport across cell membranes, matched to the AQA A Level Biology (7402) specification and written in Paper 1, Paper 2 and Paper 3 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.
