Question

A student prepared some plant cells taken from an onion. She placed the cells in a few drops of distilled water. She then used a camera attached to a microscope to photograph the cells. She then added a few drops of concentrated salt solution to the cells and waited a few minutes. She then took another photograph of the same cells. a) Describe the differences in the appearance of the cells in concentrated salt solution compared with the cells in distilled water. [2] b) The student thought that the differences in the cells were caused by osmosis. What is meant by the term osmosis? c) Explain what happens to the cells in concentrated salt solution to change their appearance. [3] d) Another student investigated the appearance of red blood cells in distilled water and in concentrated salt solution. Use your knowledge of osmosis and the structure of red blood cells to describe and explain what the red blood cells would look like i) in distilled water [2] ii) in concentrated salt solution​

Answer 1

Answer:

a)  When plant cells are placed in salt solution their appearance is different to when they are placed in distilled water. ... Therefore, water moves out of the cell across the partially permeable membrane by osmosis and the cell becomes flaccid as the cell membrane peels away from the cell wall..

2) Osmosis, the spontaneous passage or diffusion of water or other solvents through a semipermeable membrane (one that blocks the passage of dissolved substances—i.e., solutes)..

3) When a plant cell is placed in concentrated salt solution, water concentration inside the cell is greater than that which is outside the cell. Therefore, water moves through the cell membrane into the surrounding medium. ... The cell then swells to become turgid. It is called deplasmolysis..

i) Distilled water on the other hand is hypotonic to red blood cells. The red blood cell will therefore swell and haemoglobin, containing the haem that gives the red colour to erythrocytes, leaks from the cell resulting in a transparent red-pink-coloured solution..

ii) Red blood cells placed in a solution with a lower water concentration compared to their contents (eg 1.7 per cent salt solution) will lose water by osmosis and shrink. Water will diffuse from a higher water concentration inside the cell to a lower water concentration outside the cell...