Short Answer Questions Type-II (Answer in about 30-40 words) :
1. How does the bacterium Lactobacillus help in curd formation ?
2. In bread making, why does dough rise when yeast is added to it ?
3. What is the role of bacteria in increasing soil fertility ?
4. What are the various advantages of food preservation ?
5. How does a vaccine work?
Answers
1.Ans:- When milk is heated to a temperature of 30-40 degrees centigrade and a small amount of old curd added to it, the lactobacillus in that curd sample gets activated and multiplies. These convert the lactose into lactic acid, which imparts the sour taste to curd.
2.Ans:- Yeast feeds on the sugar contained with the dough, producing carbon dioxide and alcohol, in a process called fermentation.
During bread making, the dough is left in a warm place.
3.Ans:-Bacteria increase soil fertility through nutrient recycling such as carbon, nitrogen, sulphur and phosphorus. Bacteria decompose dead organic matter and release simple compounds in the soil, which can be taken up by plants.
4.Ans:-It decreases the food wastage. It increases the storage period of perishable food materials. It ensures the all year availability of seasonal food materials.
5.Ans:-A vaccine works by training the immune system to recognize and combat pathogens, either viruses or bacteria. To do this, certain molecules from the pathogen must be introduced into the body to trigger an immune response. These molecules are called antigens, and they are present on all viruses and bacteria.
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