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Q68 (IAS/2022) Science & Technology › Biotechnology & Health › Human nutrition and health Official Key

Consider the following statements in respect of probiotics : 1. Probiotics are made of both bacteria and yeast. 2. The organisms in probiotics are found in foods we ingest but they do not naturally occur in our gut. 3. Probiotics help in the digestion of milk sugars. Which of the statements given above is/are correct ?

Result
Your answer: —  ·  Correct: C
Explanation

The correct answer is Option 3 (1 and 3) because of the following reasons:

  • Statement 1 is correct: Probiotics are live microorganisms intended to provide health benefits. While bacteria (like Lactobacillus and Bifidobacterium) are the most common, certain types of yeast, such as Saccharomyces boulardii, are also widely recognized and used as probiotics.
  • Statement 2 is incorrect: Probiotics are not foreign to the human body. Many of the organisms found in probiotic supplements and fermented foods already occur naturally in the human gut microbiota. They are part of the existing internal ecosystem that maintains digestive health.
  • Statement 3 is correct: Probiotics, particularly lactic acid bacteria, produce the enzyme lactase. This enzyme helps break down lactose (milk sugar), thereby assisting in the digestion of dairy products and reducing symptoms for individuals with lactose intolerance.

Since statements 1 and 3 are scientifically accurate and statement 2 is factually wrong, Option 3 is the right choice.

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Don’t just practise – reverse-engineer the question. This panel shows where this PYQ came from (books / web), how the examiner broke it into hidden statements, and which nearby micro-concepts you were supposed to learn from it. Treat it like an autopsy of the question: what might have triggered it, which exact lines in the book matter, and what linked ideas you should carry forward to future questions.
Q. Consider the following statements in respect of probiotics : 1. Probiotics are made of both bacteria and yeast. 2. The organisms in pro…
At a glance
Origin: From standard books Fairness: High fairness Books / CA: 10/10 · 0/10

This is a classic 'Science in Everyday Life' question derived directly from lower-standard NCERTs (Class 7 & 8). The strategy is simple: Do not ignore the 'Activity' boxes and 'Did You Know' sections in basic science books. The question tests fundamental biological literacy (gut flora, fermentation) rather than advanced biotechnology.

How this question is built

This question can be broken into the following sub-statements. Tap a statement sentence to jump into its detailed analysis.

Statement 1
Are probiotics composed of both bacteria and yeast?
Origin: Direct from books Fairness: Straightforward Book-answerable
From standard books
Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 2: The Invisible Living World: Beyond Our Naked Eye > Activity 2.8: Let us perform > p. 21
Presence: 4/5
“In addition to yeast, some bacteria, such as Lactobacillus, help in fermentation of batter for making idli and dosa, and dough for making bhatura.”
Why this source?
  • Explicitly names yeast and bacteria (Lactobacillus) as separate microbes that both assist fermentation of food.
  • Shows both groups perform beneficial fermentation roles in similar food contexts (idli, dosa, dough).
Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 2: The Invisible Living World: Beyond Our Naked Eye > Table 2.4: Testing for curd formation using milk in different conditions > p. 22
Presence: 4/5
“Fig. 2.12: Root nodules of Cowpea plant which contain Rhizobium You will observe that in bowl A, the milk has turned into curd after a few hours and has become little sour. Whereas in bowl B, the milk has not curdled, but it might be a little sour. Do you know why this happens? The curd contains several types of bacteria. One of them is Lactobacillus. This bacterium feeds on the sugar in the milk (lactose), multiplies, and ferments the milk to form curd. Instead of producing alcohol (like yeast), these bacteria produce lactic acid, which makes curd sour. These bacteria grow well in warm conditions.”
Why this source?
  • Describes Lactobacillus as a bacterium used in curd formation (a beneficial microbial process).
  • Contrasts bacterial lactic acid production with yeast alcohol production, demonstrating both types have distinct useful roles.
Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 2: The Invisible Living World: Beyond Our Naked Eye > Snapshots > p. 25
Presence: 4/5
“• Microorganisms can be beneficial or harmful to us.• Some microorganisms decompose the plant and animal waste into simple substances and clean up the environment.• Some microorganisms reside in the root nodules of legumes, such as peas, beans, and lentils. They trap nitrogen from the air and increase the soil fertility.• Yeasts are fungi which are used in the process of making breads, cakes, pastries, idlis, dosas, and bhaturas.• Lactobacillus is used in the curd formation at home and fermentation process in food industry.”
Why this source?
  • States yeasts are used in making breads and similar foods and separately names Lactobacillus for curd formation, showing both are used beneficially in food.
  • Affirms microorganisms can be beneficial, linking both yeast and bacteria to beneficial uses.
Statement 2
Are the microorganisms used in probiotics found in foods that humans ingest?
Origin: Direct from books Fairness: Straightforward Book-answerable
From standard books
Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 2: The Invisible Living World: Beyond Our Naked Eye > Snapshots > p. 25
Presence: 5/5
“• Microorganisms can be beneficial or harmful to us.• Some microorganisms decompose the plant and animal waste into simple substances and clean up the environment.• Some microorganisms reside in the root nodules of legumes, such as peas, beans, and lentils. They trap nitrogen from the air and increase the soil fertility.• Yeasts are fungi which are used in the process of making breads, cakes, pastries, idlis, dosas, and bhaturas.• Lactobacillus is used in the curd formation at home and fermentation process in food industry.”
Why this source?
  • Identifies yeast and Lactobacillus as microorganisms used directly in making bread and curd — common foods eaten by humans.
  • Names Lactobacillus (a common probiotic genus) in the context of food fermentation and curd formation.
Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 2: The Invisible Living World: Beyond Our Naked Eye > Discover, design, and debate > p. 27
Presence: 4/5
“• z India has a long history of biogas production. One of our oldest biogas plant was set up in late 1850s. Find out about the Biogas Program initiated by the Ministry of New and Renewable Energy, Government of India.• z Fermented food items like fermented soybeans and fermented bamboo shoots are consumed as traditional food in some parts of India. With the help of your parents and teachers, list some traditional food items from your area that utilise the process of fermentation. Investigate the ingredients used in the preparation of these fermented food items; the method of preparing them; the microorganism responsible for the fermentation of the food, and the cultural and nutritional importance of the fermented food.• z Study the different parts of a macro fungus mushroom using a magnifying glass and microscope/foldscope.”
Why this source?
  • States that fermented food items are consumed as traditional foods and links specific microorganisms to their fermentation.
  • Encourages listing the microorganism responsible for fermentation of edible items, showing microbes are integral to foods humans eat.
Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 2: The Invisible Living World: Beyond Our Naked Eye > 2.4 How Are We Connected to Microbes? > p. 18
Presence: 4/5
“Can we find microorganisms in other places, too? Let us have a discussion: Have you ever seen a lemon, tomato, orange, or any other food item rot after being left outside for some time? If yes, you may have noticed a powdery or cotton-like growth on them (Fig. 2.9). This happens because they have been infected by microbes. But where did these microbes come from? How did they come in contact with the food? This happens because microorganisms can be found everywhere, be it in water, soil, air, or even in some food items. But why do microorganisms not infect the pickles and murabbas?”
Why this source?
  • Affirms that microorganisms are found in water, soil, air, and in some food items (e.g., causing fruit rot).
  • Demonstrates that microbes are present on/within foods that humans handle or consume.
Statement 3
Do the microorganisms used in probiotics naturally occur in the human gut?
Origin: Direct from books Fairness: Straightforward Book-answerable
From standard books
Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 2: The Invisible Living World: Beyond Our Naked Eye > 2.4 How Are We Connected to Microbes? > p. 18
Presence: 5/5
“18 This is because you add many spices with salt or sugar to it which act as preservatives. High concentration of salt or sugar do not allow these organisms to grow on them. You can use a foldscope or a microscope to explore surfaces of leaves, stems, roots, or any other part to see them. Like plants and animals, microorganisms also show great diversity. Some of them can even be found in extreme climatic conditions, such as hot water springs and snow cold zones as well as at moderate temperatures. You already know some of these organisms live inside our bodies, especially in our gut!”
Why this source?
  • Explicitly states that some microorganisms live inside our bodies, especially in our gut.
  • Directly establishes the human gut as a natural habitat for microorganisms.
Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 2: The Invisible Living World: Beyond Our Naked Eye > Snapshots > p. 25
Presence: 4/5
“• Microorganisms can be beneficial or harmful to us.• Some microorganisms decompose the plant and animal waste into simple substances and clean up the environment.• Some microorganisms reside in the root nodules of legumes, such as peas, beans, and lentils. They trap nitrogen from the air and increase the soil fertility.• Yeasts are fungi which are used in the process of making breads, cakes, pastries, idlis, dosas, and bhaturas.• Lactobacillus is used in the curd formation at home and fermentation process in food industry.”
Why this source?
  • Names Lactobacillus as a microbe used in curd formation, linking a known food-associated genus to the discussion.
  • Connects microbes used in foods (common probiotic sources) to the broader topic of microbial roles relevant to humans.
Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 2: The Invisible Living World: Beyond Our Naked Eye > 2.3 What Are Microorganisms? > p. 15
Presence: 4/5
“Some living organisms are made up of just one or very few cells. They are so small that they can not be seen with the naked eye. These are called microorganisms. Some microorganisms, like bacteria and Amoeba, are made of just one cell (unicellular). Others, like some fungi and algae, have many cells (multicellular). They are found all around us—in water, soil, air, and even inside our body! But what do their cells look like? Are they like the plant and animal cells we just learnt about, or are they different? To observe the cells of a microorganism, again, we need to use a microscope which magnifies their size and makes them visible to us.”
Why this source?
  • Affirms microorganisms are found all around us, including inside our body.
  • Reinforces the general point that the human body (and by extension the gut) naturally hosts microbes.
Statement 4
Do probiotics help in the digestion of milk sugars (lactose) in humans?
Origin: Direct from books Fairness: Straightforward Book-answerable
From standard books
Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 2: The Invisible Living World: Beyond Our Naked Eye > Table 2.4: Testing for curd formation using milk in different conditions > p. 22
Presence: 5/5
“Fig. 2.12: Root nodules of Cowpea plant which contain Rhizobium You will observe that in bowl A, the milk has turned into curd after a few hours and has become little sour. Whereas in bowl B, the milk has not curdled, but it might be a little sour. Do you know why this happens? The curd contains several types of bacteria. One of them is Lactobacillus. This bacterium feeds on the sugar in the milk (lactose), multiplies, and ferments the milk to form curd. Instead of producing alcohol (like yeast), these bacteria produce lactic acid, which makes curd sour. These bacteria grow well in warm conditions.”
Why this source?
  • Identifies Lactobacillus as a bacterium that feeds on the sugar in milk (lactose) and ferments milk to form curd.
  • Explains the biochemical outcome: lactose is consumed and lactic acid is produced, demonstrating microbial breakdown of milk sugar.
Science-Class VII . NCERT(Revised ed 2025) > Chapter 9: Life Processes in Animals > FASCINATING FACTS > p. 127
Presence: 4/5
“The large intestine contains various small living organisms, such as bacteria, that help in digestion. They help in keeping our digestive system healthy. They break down undigested food, especially fi bre, and produce essential nutrients. Fibre-rich food, and especially 'fermented foods' (like curd, buttermilk, shrikhand, kanji, pickles, gundruk, and poita bhat) are good for a healthy digestive system and overall well-being.”
Why this source?
  • States that intestinal bacteria help digestion and keep the digestive system healthy.
  • Specifically highlights fermented foods (like curd) as beneficial for digestive health, linking fermented microbes to digestive aid.
Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 2: The Invisible Living World: Beyond Our Naked Eye > 2.4 How Are We Connected to Microbes? > p. 18
Presence: 3/5
“You have studied in the chapter 'Life Processes in Animals' in Curiosity, Grade 7 that our intestine has many bacteria that help in digestion. Like plants and animals, microorganisms vary in shape, size, and structure. In Tables 2.1 and 2.2, you would have observed microorganisms of different shapes—spherical, rod-shape, or irregular. How does the diversity of microorganisms play a role in our daily life? How do they help clean the environment?”
Why this source?
  • Affirms that the human intestine contains many bacteria that help in digestion.
  • Links microbial diversity to roles in daily life including assistance in digestive processes.
Pattern takeaway: UPSC creates 'High-Tech' sounding questions from 'Low-Tech' General Science textbooks. They frame statements that sound plausible to a layman but contradict basic biological principles (like the existence of the human microbiome). Trust basic NCERT logic over complex current affairs magazines.
How you should have studied
  1. [THE VERDICT]: Sitter. Direct lift from NCERT Class VIII Science, Chapter 2 ('Microorganisms: Friend and Foe') and Class VII ('Nutrition in Animals'). If you know basic biology, Statement 2 is logically absurd.
  2. [THE CONCEPTUAL TRIGGER]: 'Application of Microbiology in Daily Life'. UPSC loves asking about things you eat (Probiotics, Trans fats, Artificial Sweeteners) or household chemistry.
  3. [THE HORIZONTAL EXPANSION]: 1. Prebiotics (fiber/food for bugs) vs Probiotics (live bugs) vs Synbiotics (both). 2. Key Strains: Lactobacillus (Lactic acid) vs Saccharomyces cerevisiae (Yeast/Alcohol). 3. Gut Flora functions: Synthesis of Vitamin K and B12. 4. Nitrogen Fixers: Rhizobium (Symbiotic) vs Azotobacter (Free-living). 5. Food Preservatives in NCERT: Sodium benzoate, Sodium metabisulphite.
  4. [THE STRATEGIC METACOGNITION]: When reading Science NCERTs, categorize microbes into 3 buckets: Industrial (Curd/Alcohol), Medicinal (Antibiotics/Vaccines), and Agricultural (Nitrogen fixation). Statement 2 was a logic trap—if probiotics 'restore' gut health, they must be native to the ecosystem. A foreign invasive species wouldn't be a 'probiotic'.
Concept hooks from this question
📌 Adjacent topic to master
S1
👉 Microorganisms in food fermentation
💡 The insight

Both yeast and bacteria are used as agents of fermentation in making breads, idlis, dosas and curd.

High-yield for questions on food technology, nutrition and microbiology; links to agriculture and industry (fermentation, dairy processing). Understanding which microbes are used where helps answer applied and policy-style questions on food security and processing.

📚 Reading List :
  • Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 2: The Invisible Living World: Beyond Our Naked Eye > Activity 2.8: Let us perform > p. 21
  • Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 2: The Invisible Living World: Beyond Our Naked Eye > Snapshots > p. 25
  • Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 2: The Invisible Living World: Beyond Our Naked Eye > Table 2.4: Testing for curd formation using milk in different conditions > p. 22
🔗 Anchor: "Are probiotics composed of both bacteria and yeast?"
📌 Adjacent topic to master
S1
👉 Basic cellular differences: bacteria vs fungi (yeast)
💡 The insight

Yeast are unicellular fungi with cell walls, while bacteria lack a well-defined nucleus—key for distinguishing the two groups.

Core for classification and biotechnology topics; aids in questions on microbial physiology, antibiotic targets and industrial use of microbes. Clarifies why bacteria and yeast behave differently in fermentation and reproduction.

📚 Reading List :
  • Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 2: The Invisible Living World: Beyond Our Naked Eye > 2.5 Why Is Cell Considered to Be a Basic Unit of Life? > p. 24
  • Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 2: The Invisible Living World: Beyond Our Naked Eye > 2.5 Why Is Cell Considered to Be a Basic Unit of Life? > p. 23
🔗 Anchor: "Are probiotics composed of both bacteria and yeast?"
📌 Adjacent topic to master
S1
👉 Beneficial versus harmful roles of microbes
💡 The insight

Microorganisms encompass both helpful agents (fermentation, nitrogen fixation) and harmful agents, so beneficial microbes include bacteria and yeast.

Important for environment, public health and agriculture segments of the syllabus; enables reasoning on interventions (probiotics, bioremediation, crop management) and framing policy/ethical questions on microbial use.

📚 Reading List :
  • Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 2: The Invisible Living World: Beyond Our Naked Eye > Snapshots > p. 25
  • Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 2: The Invisible Living World: Beyond Our Naked Eye > Activity 2.8: Let us perform > p. 21
🔗 Anchor: "Are probiotics composed of both bacteria and yeast?"
📌 Adjacent topic to master
S2
👉 Microbes in fermented foods
💡 The insight

Fermented foods routinely contain microorganisms that perform fermentation and are consumed by humans.

High-yield for questions on food technology, nutrition, and traditional practices; links microbiology to agriculture and public health. Mastery helps answer questions on food processing, cultural foods, and microbial roles in industry.

📚 Reading List :
  • Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 2: The Invisible Living World: Beyond Our Naked Eye > Discover, design, and debate > p. 27
  • Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 2: The Invisible Living World: Beyond Our Naked Eye > Snapshots > p. 25
🔗 Anchor: "Are the microorganisms used in probiotics found in foods that humans ingest?"
📌 Adjacent topic to master
S2
👉 Key beneficial food microbes: Lactobacillus and yeast
💡 The insight

Lactobacillus and yeast are explicitly used in curd and bread production and represent microbes people ingest in foods.

Important for questions on probiotics, fermentation, and biotechnology applications; connects to human health, gut microbiota, and food industries. Enables targeted answers about specific genera used in food production.

📚 Reading List :
  • Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 2: The Invisible Living World: Beyond Our Naked Eye > Snapshots > p. 25
  • Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 2: The Invisible Living World: Beyond Our Naked Eye > Activity 2.8: Let us perform > p. 21
🔗 Anchor: "Are the microorganisms used in probiotics found in foods that humans ingest?"
📌 Adjacent topic to master
S2
👉 Ubiquity of microorganisms including in food items
💡 The insight

Microorganisms occur in the environment and on some foods, causing both spoilage and beneficial fermentation.

Useful for environment and sanitation topics, decomposition, and food safety; helps frame policy or science questions about preservation, contamination, and microbial ecology.

📚 Reading List :
  • Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 2: The Invisible Living World: Beyond Our Naked Eye > 2.4 How Are We Connected to Microbes? > p. 18
  • Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 2: The Invisible Living World: Beyond Our Naked Eye > 2.3 What Are Microorganisms? > p. 15
🔗 Anchor: "Are the microorganisms used in probiotics found in foods that humans ingest?"
📌 Adjacent topic to master
S3
👉 Microbes inhabit the human gut
💡 The insight

The human gut is a natural habitat for many microorganisms, which is the essential context for asking whether probiotic microbes occur there.

High-yield for questions linking microbiology to human physiology, health, and nutrition; helps explain host–microbe interactions, digestion, and immunity. Mastery allows candidates to connect biological facts to public health and food policy questions.

📚 Reading List :
  • Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 2: The Invisible Living World: Beyond Our Naked Eye > 2.4 How Are We Connected to Microbes? > p. 18
  • Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 2: The Invisible Living World: Beyond Our Naked Eye > 2.3 What Are Microorganisms? > p. 15
  • Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 2: The Invisible Living World: Beyond Our Naked Eye > Keep the curiosity alive > p. 26
🔗 Anchor: "Do the microorganisms used in probiotics naturally occur in the human gut?"
🌑 The Hidden Trap

From the same NCERT Chapter 2: The distinction between 'Antibiotics' (bacteria/fungi derived) and 'Antibodies' (body produced). Expect a question on specific antibiotic sources (Penicillin from Fungi/Mold) or the 'Pasteurization' process (heating to 70°C then sudden chilling) which is on the very next page.

⚡ Elimination Cheat Code

Apply the 'Restoration Logic' to Statement 2. The statement says probiotic organisms 'do not naturally occur in our gut.' If they were alien to our gut, the body would attack them as pathogens. The entire medical concept of probiotics is to *replenish* natural flora lost due to antibiotics or illness. This contradiction eliminates Statement 2, leaving Option C (1 and 3) as the only answer.

🔗 Mains Connection

Link Gut Microbiome to GS-2 (Health) & GS-3 (Economy/Agriculture). Poor gut health (Environmental Enteropathy) due to lack of sanitation reduces nutrient absorption, leading to 'Stunting' and 'Malnutrition' despite food intake. This links Swachh Bharat Abhiyan directly to nutritional outcomes.

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SIMILAR QUESTIONS

IAS · 2008 · Q42 Relevance score: 3.98

Consider the following statements about probiotic food: 1. Probiotic food contains live bacteria which are considered beneficial to humans. 2. Probiotic food helps in maintaining gut flora. Which of the statements given above is/are correct?

CDS-I · 2013 · Q63 Relevance score: 1.37

Consider the following statements regarding antibiotics: 1, They are used to destroy disease causing bacteria. 2. They can be applied to the skin, swallowed or injected to fight micro-organisms inside the body, 3. They are effective against disease-causing viruses. 4. The first antibiotic to be discovered was tetracycline. Which of the statements given above is/are correct ?

CDS-I · 2003 · Q113 Relevance score: 0.46

With reference to the digestion of food in human beings, consider the following statements: I. Digestion of the milk protein, casein is initiated in the duodenum with its coagulation. II. Trypsin hydrolyses casein into paracasein and whey proteins Which of these statements is/are correct?

CAPF · 2019 · Q5 Relevance score: -0.08

Which one of the following statements is correct?

IAS · 2004 · Q12 Relevance score: -0.21

Consider the following statements: 1. Toothless mammals such as pangolins are not found in India. 2. Gibbon is the only ape found in India. Which of the statements given above is are correct?