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Teeth and the World of Microbes - Microbes: Useful and Harmful

Grade 4CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

Microbes are extremely tiny living organisms that can only be seen through a device called a microscope.

The four main types of microbes are Bacteria, Viruses, Protozoa, and Fungi.

Useful microbes include Lactobacillus which helps in turning milk into curd and Yeast which helps in making bread and cakes soft.

Harmful microbes are also known as germs or pathogens and cause various diseases.

Bacteria are responsible for diseases such as typhoid, tuberculosis, and tooth decay caused by the production of acid from sugars.

Viruses cause illnesses like the common cold, influenza, and COVID19COVID-19.

Protozoa are responsible for diseases like malaria and amoebic dysentery.

Fungi can cause skin infections such as ringworm and athlete's foot.

Microbes also play a vital role in nature by decomposing dead plants and animals, which enriches the soil with nutrients.

📐Formulae

MilkLactobacillusCurd\text{Milk} \xrightarrow{\text{Lactobacillus}} \text{Curd}

Sugar+BacteriaAcidTooth Decay\text{Sugar} + \text{Bacteria} \rightarrow \text{Acid} \rightarrow \text{Tooth Decay}

SugarYeastAlcohol+CO2\text{Sugar} \xrightarrow{\text{Yeast}} \text{Alcohol} + CO_2 \uparrow

💡Examples

Problem 1:

Explain how yeast makes the dough rise when baking bread.

Solution:

Yeast reacts with the sugar present in the dough to produce CO2CO_2 gas.

Explanation:

As the yeast consumes sugar, it undergoes fermentation and releases Carbon Dioxide (CO2CO_2). This gas gets trapped in the dough, forming bubbles that make the bread rise and become soft and fluffy.

Problem 2:

Which microbe is responsible for causing Malaria, and how is it spread?

Solution:

Malaria is caused by a type of Protozoan called Plasmodium.

Explanation:

The protozoan is carried by the female Anopheles mosquito. When the mosquito bites a person, it transfers the microbe into the bloodstream.

Problem 3:

How do microbes help in maintaining the cleanliness of the environment?

Solution:

Microbes act as decomposers.

Explanation:

Saprophytic microbes break down the complex organic matter of dead plants and animals into simpler substances. This process cleans the environment and recycles nutrients back into the soil.