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Date	November 2019	Marks available	2	Reference code	19N.3.SL.TZ0.1
Level	Standard level	Paper	Paper 3	Time zone	TZ0 / no time zone
Command term	Evaluate	Question number	1	Adapted from	N/A

Question

An experiment was carried out on osmosis in carrot (Daucus carota) root tissue and potato (Solanum tuberosum) tuber tissue. Similar sized pieces of tissue were cut and soaked in different sucrose solutions for 24 hours. The results are shown in the graph below.

Using the graph, estimate isotonic sucrose solutions for potato tissue and carrot tissue.

Potato:

Carrot:

[2]

a.

Suggest a reason for the difference in the isotonic points for the potato and the carrot tissues.

[1]

b.

From the evidence provided by the graph, evaluate the reliability of these data.

[2]

c.

Explain one reason for calculating the percentage change in mass.

[2]

d.

Markscheme

potato: 0.26 mol dm^–3 ✔ Allow a range of 0.22–0.32
carrot: 0.50 mol dm^–3 ✔ Allow a range of 0.45–0.55 (Allow 1 max if no units or either unit is omitted)

a.

different dissolved solutes/sugars/sucrose/salts/molarities ✔
OR
may have been grown in different soils giving their tissues different contents ✔
OR
may have been stored under different conditions ✔
OR
may be more dehydrated / different water content ✔
OR
different types of tissue / different age ✔

Do not accept starch.

b.

a. the data show clear trends
OR
a trend line could be drawn through these data
OR
there are no outliers ✔

b. the error bars/standard deviations shown
OR
the error bars/standard deviations vary with concentration ✔

c. sample size is unknown ✔

c.

a. the change in mass indicates whether the tissue has gained/lost water ✔

b. the pieces of tissue will not be the same mass «at the beginning of the experiment» ✔

c. to compare the relative changes in mass ✔

d.

Examiners report

[N/A]

a.

[N/A]

b.

[N/A]

c.

[N/A]

d.

Syllabus sections

Core » Topic 1: Cell biology » 1.4 Membrane transport

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[Source: Zaidan, T. , de Matos, W. , Machado, É. , Junqueira, T. , Vicentini, S. , Presta, G. and Santos-Filho, S. (2010)
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