Cell Biology: Osmosis and Osmosis Required Practical

Question 1

Define osmosis.

Answer 1

Osmosis is the spreading out of water molecules across a partially permeable membrane, from an area of high water concentration to an area of lower water concentration.

Question 2

Describe how you would prepare 3 identical cyclinders to investigate the effect of osmosis on plant tissue.

Answer 2

1. Peel potato.
2. Use a cork borer to produce 3 cylinders of potato.
3. Use a scalpel to trim the cylinders to the same length (3cm)
4. Measure the length and mass of each cylinder using a ruler and a balance.

Question 3

How would you investigate the effect of osmosis on plant tissue once you’ve prepared 3 identical cylinders?

Answer 3

1. Place each cylinder into a test tube.
2. Add 10cm³ of 0.5, 0.25 molar solution and distilled water to each test tube.
3. Leave cylinders overnight to allow osmosis to take place.
4. Remove cylinders and gently roll them on a paper towel to remove any surface moisture.
5. Measure the length and mass of cylinders again.
6. Calculate the percentage change in length and mass.

Question 4

How would you use a graph plotting percentage change in mass against concentration of sugar solution to estimate the concentration of water inside the cell? Why?

Answer 4

The point where the line crosses the x axis.
This shows no change in mass. as the concentration outside the cell is the same as the concentration inside.
Therefore no overall osmosis has taken place.