Important Questions for Class 8 Chapter 2 - Microorganisms : Friend and Foe

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Important questions based on NCERT syllabus for Chapter 2 - Microorganisms : Friend and Foe:

Question-1: Why are antibiotics not effective against cold and flu? Why do antibiotics work on bacterial infections only?

Solution: Cold and flu are caused by viruses.
Viruses insert their genetic material into a human cell's DNA in order to reproduce. Antibiotics cannot kill viruses, unlike bacteria, viruses have different mechanisms and machinery to survive and replicate. The antibiotic has no “target” to attack in a virus. In a bacteria, the antibiotic works by keeping a bacterium from building a cell wall.The bacterium is unable to replicate and dies.

Question-2: How are vaccines related to antibodies produced by our body? Are vaccines safe?

Solution: When a disease-carrying microbe enters our body, the body produces antibodies to fight the invader. The antibodies remain in the body and we are protected from the disease-causing microbes. This is how a vaccine works.

Vaccines can sometimes cause a mild reaction, such as soreness at the injection site or a slight fever. However, there are usually no serious adverse events associated with immunisation. Severe allergic reactions or serious side effects very rarely occur. But people with weakened immune systems and pregnant women are vulnerable to the disease and should consult their doctor before being vaccinated.

Question-3: Give two examples of food items that’s prepared by the help of microorganism other than curd? How is curd formed?

Solution: The examples for food items that are produced with the help of microorganisms other than curd are

  1. Cheese
  2. Pickle
    When pasteurised milk is heated to a temperature of 30-40 °C, or even at room temperature and a small amount of old curd or whey added to it, the lactobacillus in that curd starts to grow. These convert sugars that is lactose into lactic acid by means of fermentation into lactic acid and curd is formed.