1
Q
Explain the phenomenon of plant wilting. (5)
A
- excessive use of fertilisers may cause wilting in plants
- dissolved fertiliser causes soil water to be hypertonic to the sap cell of roots
- water diffuse by osmosis from the roots’ cell sap to the soil
- cells become plasmolysed
- if period of plasmolysis is prolonged, wilted plants will eventually die
2
Q
What are the applications of movement of substances across a plasma membrane in our daily life? (4)
A
- rehydration drinks help to recover loss of water & electrolytes in individuals with diarrhoea
- isotonic drinks help athletes recover water loss & electrolytes through perspiration
- saline solutions are isotonic to the blood plasma
- liposomes (vesicles that contain aqueous solution surrounded by phospholipid bilayer membrane) are used to protect drug/active substances taken orally from being destroyed by gastric juices. Hence, drugs can reach they’re target cells
3
Q
What is reverse osmosis & how is it done? (4)
A
- a technology used to extract fresh water from seawater using desalination process
- pressure is applied to push the seawater through a semi-permeable membrane
- the membrane allows water particles to pass through it but not foreign particles, salt & microorganisms
- Hence, only pure fresh water is released
