Formative Practice 3.4 (Form 4 Biology Textbook Exercise and Answer)

Question 1:
Explain why green chillies are preserved using vinegar and sugar.

The concentrated sugar solution is hypertonic to the cell sap of chili. Water diffuses out of the chili via osmosis. The chilli undergoes dehydration. Bacteria is unable to survive without water. Thus, pickled green chili can be kept for a long time.

Vinegar reduces pH. Bacteria also cannot live in an acidic environment.

Question 2:
Pickled pineapples are prepared by soaking the pineapple pieces in a thick sugar solution. State two advantages and disadvantages of this method as compared with keeping fresh pineapples.

Two advantages:
• Prevents wastage due to spoilage.
• Preserved pineapples last longer.

Two disadvantages:
• Pineapples contain too much sugar.
• Nutrients are damaged by oxidation during preparation. This causes the preserved pineapple pieces to have low nutrients.

Question 3:
Ariana had diarrhoea after eating stale food. Suggest something that can help her to recover.

Ariana can take rehydration drinks such as oral rehydrating salts. Ingestion of this drink can replace the water and electrolytes lost due to diarrhoea.

Question 4:
A liposome is a vesicle that contains an aqueous solution that is surrounded by a phospholipid bilayer membrane. Explain the use of liposomes in everyday life.

Liposomes are used to protect medicine or active substances that are eaten orally from being destroyed by gastric juices. This way, the medicine can reach target cells effectively.

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