Water Potential (HL IB Biology)

The cell walls of three plant cells are in contact with each other. The water potentials inside each cell are shown in the table.

Describe how water will move between the three cells.

Some onion cells were placed in distilled water for several hours, a light micrograph image of the cells can be seen below:

Describe and explain the changes to water potential in these cells.

Another group of cells appears as follows under the microscope:

Explain why these cells differ in appearance from the cells shown in part (b).

Emphysematous pyelonephritis (EPN) is a very rare complication that can develop as a result of an untreated kidney infection. It is a severe infection during which bacteria destroy kidney tissue, eventually leading to kidney failure. If kidney failure is left untreated the kidneys are unable to regulate the amount of water in the body and the blood plasma becomes more dilute than normal.

Describe the effect that this would have on red blood cells.

Explain why changes in cell volume affect animal cells more severely than plant cells.

A group of students carried out an experiment to investigate water movement using the following method:

1. Dice potato into 1cm³ cubes and weigh them
2. Add potato cubes to 6 test tubes, each containing a solution with a different sucrose concentration
3. Wait 12 hours
4. Weigh the cubes from each test tube and plot a graph

The mean weight of the potato cubes was 2.5g before being added to the solution and the graph shows the weights of potato cubes after the experiment. 

Identify which sucrose concentration provides an isotonic solution.

Explain your answer to part (i)

With reference to the graph in part (a), describe and explain the changes in pressure potential observed in the potato cells between 0.3 M and 1 M sucrose solution.

Sketch one of the potato cells that was kept in the 1.00 M sucrose solution. Label the cell wall, cell membrane and cytoplasm in your diagram.

Using the data from (a), calculate the percentage change in mass for the potato cylinders in 0.2 M sucrose solution.