[Maximum number: 7]

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.

(a)

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

Potato:
Carrot:

[ 2 ]

(b)

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

[ 1 ]

(c)

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

[ 2 ]

(d)

Explain one reason for calculating the percentage change in mass.

[ 2 ]

[Maximum number: 2]

The image was obtained with a mobile phone camera pointing down the eyepiece tube of a light microscope. It shows onion (Allium cepa) epidermal cells after immersion in a hypertonic salt solution during an experiment on osmosis.

$\times 150$

(a)

(i)

Explain the effect of the salt solution on these cells.

[ 2 ]

(a)

A study was done on the osmolarity of semen and sperm movement (motility).

[ 1 ]

(i)

The same study showed that blood plasma has a lower osmolarity than semen. Explain how that would affect the movement of water between blood plasma and semen.

[ 1 ]

(b)

Explain a change that would take place in sperm placed in a hypotonic solution.

[ 1 ]

[Maximum number: 2]

The micrograph shows part of a cardiac muscle cell.

(a)

Explain the changes that would occur in a cardiac muscle cell placed in a hypotonic solution.

[ 2 ]

[Maximum number: 5]

Data was collected on rabbit red blood cells that were exposed to sodium chloride (NaCl) and scorpion venom. Under some osmotic conditions red blood cells swell and burst, releasing hemoglobin (hemolysis). The graph shows the response of red blood cells to different concentrations of sodium chloride, with and without scorpion venom.

(a)

Outline the effect of the venom on the hemolysis of red blood cells.

[ 2 ]

(b)

Describe how the variables would be controlled in an experiment to estimate the osmolarity of plant tissue.

[ 3 ]

[Maximum number: 5]

An experiment was carried out to determine the change in mass due to osmosis. Potato cubes were soaked in different concentrations of sodium chloride for 12 hours. The table shows the mean data for the mass of potato before and after the 12-hour period.

(a)

Outline the conditions necessary for osmosis to occur.

[ 2 ]

(b)

Explain how the data may be used to determine the solute concentration of the potato tissue.

[ 2 ]

(c)

Estimate the solute concentration of the potato tissue.

[ 1 ]

[Maximum number: 3]

Solutions of ions, for example NaCl dissolved in water, can be used to investigate the concentration of solutes in plant tissues. After immersion in solutions of varying concentration, the percentage changes in mass of potato samples were measured. The graph shows the results.

(a)

(i)

Estimate the osmolarity of the plant tissue.
moles $\mathrm{dm}^{-3}$

[ 1 ]

(ii)

Identify which part of the graph represents samples measured in a hypotonic solution.

[ 1 ]

(iii)

State one possible source of error when collecting data during this experiment.

[ 1 ]

[Maximum number: 3]

An experiment was carried out to measure the osmolarity of cantaloupe (fruit of Cucumis melo) tissue by placing pieces in salt solutions of different concentrations. The results are shown in the graph.

Removed for copyright reasons

(a)

(i)

Identify the concentration of salt solution with an osmolarity equal to that of the cantaloupe tissue.

[ 1 ]

(b)

Describe two factors that should be kept constant in this experiment in order to obtain an accurate measurement of the osmolarity of the cantaloupe tissue.

[ 2 ]

[Maximum number: 1]

The micrograph shows a human cheek cell magnified with a light microscope.

(a)

Describe what would happen to the cheek cell if it was placed in a hypertonic salt solution.

[ 1 ]

[Maximum number: 1]

The salt concentration inside the Paramecium is 1.8 %. The salt concentration in the surrounding medium suddenly drops to 0.2 %. What will be the likely response?

The cell will lose salt to the medium.

The contractile vacuole will expel more water.

The cell will swell and eventually burst.

The membrane will become more permeable to salt.