10. Read the passage and answer the following questions.
It was a cold winter evening. John
was helping his mother in the kitchen. His mother was about to set
John was confused how milk will convert into curd and how a woollen cloth helps in this process. Help
him by answering the following questions.
a. Microorganisms such as a type of bacteria help in the conversion of milk to curd. Are bacterial
cells similar to plants and animals? Give reasons to your answers.
(1.5)
b. What is the type of change taking place here: physical or chemical? Give evidence to support
your answer. (1.5)
C. Why did mother ask John to bring the woollen cloth to set the curd?
(1)
Answers
Explanation:
a)ans
bacteria like lactobacillus help in the process of converting milk into curd
Answer:
a) Lactic acid bacteria(LAB) helps in the conversion of milk
to curd.There are some similarities between bacterial
and animal plant cells.Those are the cell wall( but
different composition) , cell membrane.
There are more differences between them.Cell wall
composition is different, cell membrane type is
different, type of ribosomes are different and etc.
b) It is a chemical change.The bacteria breakdown the
lactose in milk to lactic acid.This increases the acidity
of milk due to which the milk protein casein coagulates
as curd.
c) The temperature must be warm enough for the microbe
to multiply.So, woollen cloth helps to maintain warm
temperature.