Help in Making Different Foods


Help in Making Curd

Curd is prepared by small amount of curd in warm milk

This curd contains bacteria called  (Lactobacillus) which multiplies in milk and convert it into curd.Lactose is a sugar present in the milk. (It converts lactose in milk to lactic acid which makes curd)



Help in Making Bread

Yeast is a kind of fungus(called khamir in hindi)

It is mixed in dough

Yeast reproduces rapidly and gives Carbondioxide during respiration

This makes bread to rise and increase volume

Rice idli,Dosa Batter and breads are prepared by fermentation of bacteria and yeast






Help in Making Alcohol

Note - yeast is a kind of fungus(called khamir in hindi)

Yeast is grown on natural sugars present in grains like wheat,barley,maize etc

Yeast converts sugar into alcohol by process called fermentation(Fermentation was discovered by Louis Pasteur in 1857)





Help in Making Medicines


They are used in preparation of antibiotics

Antibiotic medicines contain these good microorganisms which enter our body and kill harmful microorganisms

Example - Penicillin, Streptomycin, tetracycline and erythromycin.

Antibiotics are also used to control many plant diseases. 



They also help in preparing vaccines which prevents diseases

These vaccines help the body in making antibodies which fight these microorganisms and prevent diseases in future


Polio Drops are given to children


Help in Increasing Fertility of Soil


Help in Cleaning Environment

Plants and Animal Wastes are decomposed into manure with the help of bacteria



NCERT Question Q2 (e) - Tick the correct answer:

The bread or idli dough rises because of

(i) heat (ii) grinding (iii) growth of yeast cells (iv) kneading

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NCERT Question  Q3 - Match the organisms in Column I with their action in Column II

Column II

Column II

(i) Bacteria

(a) Fixing Nitrogen

(ii) Rhizobium

(b) Setting of curd

(iii) Lactobacillus

(c) Baking of bread

(iv) Yeast

(d) Causing Malaria

(v) A protozoan

(e) Causing Cholera

(vi) A Virus

(f) Causing AIDS


(g) Producing antibodies

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NCERT Question Q1 (c) -  Alcohol is produced with the help of __________.

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NCERT Question Q2 (a) - Tick the correct answer:

Yeast is used in the production of

(i) sugar (ii) alcohol (iii) hydrochloric acid (iv) oxygen

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NCERT Question Q2 (f) - Tick the correct answer:

The process of conversion of sugar into alcohol is called

(i) nitrogen fixation (ii) moulding (iii) fermentation (iv) infection

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NCERT Question Q7 - Write 10 lines on the usefulness of microorganisms in our lives

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Maninder Singh

CA Maninder Singh is a Chartered Accountant for the past 14 years and a teacher from the past 18 years. He teaches Science, Economics, Accounting and English at Teachoo