Three pieces of potato Ussue of a similar shape and size were cut from
the same potato, Each piece of tissue was bloted, weighed on a balance
and placed m one of three solutions of sucrose (A, B and C) The pieces
of potato were left in the solutions for an hour, then removed, Worted
again and reweighed. The results are shown in Table 2.1.
Solution Starting mass / B
Final mass /
Change in mass / %
Table 2.1
1. Copy the table and complete it by calculating the change in mass
for the pieces of potato in solutions B and C.
2. Explain the results for the potato in solution
3. Which solution is hypotonic to the potato cells?
4. Which solution is nearly isotonic to the potato cells?
Which solution has a lower water potential than the potato cells?
The cell membrane of plant cells is partially permeable Explain the
meaning of this term with reference to sucrose solution
6.
Answers
Answer:
Osmosis, the process in which solvent molecules move from an area of lower solute concentration to an area of higher solute concentration, can easily be demonstrated with potato experiments. Potatoes are full of both water and starch, and will gain water when immersed in watery solutions. Conversely, they will lose water when in concentrated solutions, such as those containing a great deal of starch. You can use potatoes to set up osmosis experiments for students of all ages and levels. and for the third solution, simply use tap water. Make three thin potato slices — 1/2 cm thick. Place each potato slice into each of the solutions, and leave the slices in the solutions for a half hour.Observe that the slice placed in salt is very flexible, while the slice placed in sugar is flexible, but less so. Since potatoes already contain sugar, less water will diffuse out of the potato placed in sugar water. The slice placed in water will be rigid, since it will absorb water.
Explanation:
Osmosis is the movement of water through membranes by diffusion. Scientists first observed and studied osmosis in the 1700s, but it is today a basic scientific concept learned at school. Through this phenomenon, animals, plants and other living beings can keep their cells hydrated. Simple experiments using potatoes can help children to understand the concept of osmosis and its importance for cell maintenance and survival.
Blackcurrant Squash
Cut four potato slices, dry them with a paper towel and weigh them. Prepare four solutions of different concentrations using black-currant or other concentrated fruit drink and water. Place one potato slice in each solution; leave for at least 15 minutes. Remove the potato slices from the solutions, dry with a paper towel and weigh them again. Compare the weights of potato slices from different solutions. Also observe the relation between the concentration of the solution and the firmness of the potato slices.
Salt and Sugar Solutions
Prepare two concentrated solutions. Add 2 tbsp. salt to a cup of water and the same quantity of sugar in another cup of water. Cut three potato cylinders or slices. Weigh and measure them. Put one potato slice in the salt solution and other in the sugar solution. The third potato slice put in a cup with water. After 24 hours, remove the potato slices and dry, weigh and measure them. Compare results and write down a hypothesis to explain them.
Salt Solutions of Different Concentrations
Use two soup plates to prepare two salt solutions. Fill the plates with water. Add 1 tbsp. salt to one plate and 1 tsp. salt to the other. Cut two slices from a potato and place one in each plate. Leave them for about two to three hours. Remove the potato slices from the water and try to bend them. Compare the results.
Effects of Temperature
Observe the effect of osmosis in potato cells in solutions with different temperatures. Prepare two identical solutions with a cup of water and 2 tbsp. salt. Heat one of the solutions in the microwave for about 30 to 45 seconds, until it is warm. Cut out two slices from a potato and place each one of them in one solution. Leave for 10 minutes, take them out and compare the results