Notes

Question 1.
Name the groups in which microorganisms are broadly classified.
Answer
Microorganisms are broadly classified in four groups:
bacteria
fungi
protozoa
algae
question 2 Write a use of yeast.
Answer:
Yeast is used in the production of alcohol, wine, beer and other beverages.
Question 3.
What does yeast produce during respiration?
Answer:
Yeast produces carbon dioxide gas during respiration
question 4 Define food preservation.
Answer:
Food preservation is the method of preserving food from being spoiled by the microbes.
question 5 What is vaccine?
Answer:
A substance which is used in the production of immunity against various diseases in the living body is termed as vaccine
question 6 What is decomposition?
Answer:
Decomposition is the process in which organic materials are broken down into simple inorganic sub-stances by the microorganisms.
question 7 Classify bacteria on the basis of their shapes.
Answer:
On the basis of their shapes, bacteria are classified into four categories:
rod-shaped bacteria (bacilli)
spherical-shaped bacteria (cocci)
curved-shaped bacteria (vibrios)
spiral-shaped bacteria (spirilla
question 8 define communicable diseases. Give some examples.
Answer:
Communicable diseases are microbial diseases that can spread from an infected person to a healthy person through air, water, or other physical contacts; e.g., cholera, chicken pox, tuberculosis, common cold, etc.
question 9 What do you mean by food spoilage?
Answer:
The process in which food is deteriorated to such extent that it does not remain fit for human consumption is known as food spoilage.
Question 10.
What role does sugar play in the preservation of food?
Answer:
The role of sugar in food preservation is significant. By adding sugar in the food item, we reduce its moisture content and hence, it stops the growth of the microorganisms.
Question 11.
How are carriers harmful to us?
Answer:
Carriers take with them many harmful microorganisms or pathogens. They play a great role in transferring these pathogens to a healthy person, by sitting on the food items, or directly transferring the pathogens inside the body of a person. Hence they are harmful to us.
Question 12.
What is the role of bacteria in increasing the soil fertility?
Answer:
Some bacteria, which are present in the root nodules of leguminous plants or free-living fix the atmospheric nitrogen in the soil which is ultimately used up by the plants. Hence they increase the fertility of the soil. For example, Rhizobium, Azotobacter, Azospirillum, etc.
Question 13.
Define Ohmic heating.
Answer:
Ohmic heating is the process in which electric current of high voltage is passed through the food items to kill the microbes that cause the spoilage of food.
Question 14.
What is sterilisation?
Answer:
The process of killing all the microorganisms above the temperature of 100°C is known as sterilisation. It is one of the widely used methods to preserve food, and is often used for various food items.
Question 15.
What is pasteurisation?
Answer:
Pasteurisation can be defined as the partial sterilisation of foods at a temperature that destroys harmful microorganisms without major changes in the chemical property of the food.
Question 16.
Explain why antibiotics do not work against flu or any infection caused by viruses.
Answer:
Viruses cannot be killed by using antibiotics as their cell pathways are different from that of bacteria. It means taking antibiotics to get rid of flu or any other viral infection is useless, because it does not re-duce the strength of the virus, nor does it reduce the duration of the infection. But, however, antibiotic will work if we get attacks of viral infection and bacterial disease at the same time. Even then, it will cure bacterial disease only but not the viral infection.
Question 17.
Mention any three ways through which pathogens are transmitted.
Answer:
Three ways because of which pathogens are transmitted are as follows:

When a person sneezes or coughs, tiny droplets containing a number of disease-causing microorganisms come out of the mouth, and are released in the air. They are transmitted to a healthy person while breathing.
By making direct contacts with an infected person, pathogens are transferred to a healthy person.
Carriers of pathogens also help in their transmission. For instance, when a fly sits on animal excreta or garbage, harmful disease-causing microbes stick to its legs. And when this fly sits on the food items, pathogens get transferred to them. This contaminated food items cause serious diseases when it is eaten by a healthy person
Question 18.
What is the difference between Rhizobium and cyanobacteria in the way of fixing nitrogen for the plants?
Answer:
Rhizobium lives in the root nodules of leguminous plants in a symbiotic relationship whereas cyanobacteria lives freely in the soil and fixes nitrogen
Question 19.
Why oil is added while making pickle?
Answer:
Oil seals off the air from the item that is being pickled and thus inhibit the growth of most of the microorganisms.
Question 20.
Explain canning.
Answer:
Canning is a process used for food preservation. Heat, at a certain temperature and for a limited period of time, is used to kill the harmful microorganisms as well as enzymes. This method also involves the removal of oxygen gas, and to avoid post-process contamination by airtight sealing of food items.