Question

Predict the effect hypertonic, hypotonic and isotonic solution will have on animal cells (red blood cells) and plant cells (elodea)

Answer 1

When an animal cell or a plant cell is placed in a medium, which is a water solution, the possible consequences are listed below.

Effects of osmosis in animal cells

1) In a hypotonic solution, the water concentration of the cytoplasm of the cell is lower than that of the medium. The effective osmosis will result in the cell gaining water. The water molecules are free to pass across the cell membrane in both directions, but more water molecules will enter the cell than will diffuse out with the result that water enters the cell, which will then swell up and could possibly burst, as Animal cells do not have cell walls to prevent excess swelling.

3)In a hypertonic solution, the water concentration inside the cell is higher than that of the medium. The effective osmosis will result in diffusion water molecules out more than that entering the cells and the cell will shrink and shrivel.

2) In an isotonic solution, the water concentration inside the cell is the same as that in the surrounding medium. Therefore, there will exist a dynamic equilibrium between the number of molecules of water entering and leaving the cell and so the cell will retain its original size.

Effects of osmosis in plant cells

1) Plant cells are enclosed by a rigid cell wall. When the plant cell is placed in a hypotonic solution, it takes up water by osmosis and starts to swell, but the cell wall prevents it from bursting. The plant cell is said to have become "turgid" i.e. swollen and hard. The pressure inside the cell rises until this internal pressure is equal to the pressure outside. This liquid or hydrostatic pressure called the turgor pressure prevents further net intake of water.

2) When a plant cell is placed in a hypertonic solution, the water from inside the cytoplasm of the cell diffuses out and the plant cell is said to have become "flaccid". If the plant cell is then observed under the microscopic, it will be noticed that the cytoplasm has shrunk and pulled away from the cell wall.This phenomenon is called plasmolysis.

3) When a plant cell is placed in an isotonic solution, a phenomenon called incipient plasmolysis is said to occur. Although the cell is not plasmolyzed, it is not turgid as well.