NCERT Solutions Curiosity Chapter 3 In-text Questions — — Proteins, and the two cases of Vitamin C and iodine

Book page 42 & 43 Updated on2026-09-05

Q1.

Which of these food components are part of your daily diet?

Answer

Check your own week's table from Activity 3.1 against the list of components. In most Indian homes the answer looks like this:

Component	In my daily diet?	From which food
Carbohydrate	Yes, at every meal	Rice, chapati, poha, potato
Protein	Yes, most days	Dal, rajma, chana, milk, curd, paneer; egg or fish in some homes
Fat	Yes	Cooking oil, ghee, butter, peanuts, coconut
Vitamins and minerals	Yes, but often too little	Green vegetables, lemon, amla, banana, milk, iodised salt
Roughage and water	Yes	Salad, whole grains, fruit; drinking water, buttermilk

What to look for honestly: almost every student's diet has enough carbohydrate. The two that often fall short are fruits and raw vegetables (vitamins, minerals, roughage) and pulses or milk (protein) — especially on days when snacks replace a proper meal.

Tip: Growing children need the right amount of protein for proper growth and development, so a bowl of dal, a glass of milk or a handful of roasted chana should not be skipped.

Q2.

Why do you think we are advised to include servings of fruits, vegetables and other plant-based foods in our daily diet?

Answer

Because fruits, vegetables and other plant foods bring us the components that cereals and oil cannot supply — the protective nutrients and roughage.

Vitamins — amla, guava, lemon and orange give Vitamin C; carrot, papaya and mango give Vitamin A; whole grains and seeds give Vitamin B₁. These protect the body from deficiency diseases.
Minerals — green leafy vegetables, beetroot and pomegranate give iron; sesame and green vegetables give calcium.
Dietary fibre (roughage) — fruits and vegetables keep the passage of stool smooth and prevent constipation.
Water — cucumber, tomato, watermelon and orange are mostly water.
Some protein and energy — pulses, beans, peas and nuts are excellent plant sources of protein.

Why plant-based food is doubly good: the book notes that eating food that is locally grown and plant-based, to the extent possible, is not only healthy for the body but is also good for our environment and our planet — it needs less land, less water and less transport.

Q3.

What do you interpret by reading Case 1? What cures scurvy?

Answer

Interpretation: the sailors' bleeding and swollen gums were not caused by the sea or by hard work — they were caused by something missing from their food. During long voyages the sailors ate only stored, dried food and no fresh fruit. James Lind noticed in 1746 that the sailors who ate lemons and oranges recovered, which showed that the missing thing was present in those fruits.

Long voyage → no fresh fruit → Vitamin C missing → bleeding, swollen gums → scurvy
Lemons and oranges eaten → Vitamin C supplied → the sailors recover

What cures scurvy: Vitamin C. Lemons and oranges cure scurvy because citrus fruits are rich in Vitamin C. Amla, guava and green chilli are even richer Indian sources.

The bigger idea in Case 1: this is the first clue in the chapter that a disease can be caused by a lack of something rather than by an infection. Such illnesses are called deficiency diseases, and the cure is food, not medicine.

Did you know? Lind's observation was also a neat piece of the scientific method — he observed, questioned, guessed, tested on the sailors and analysed the result, long before anyone knew what a vitamin was.

Q4.

What do you infer from Case 2?

Answer

Inference: the swelling at the front of the neck seen in the Himalayan region and the Northern plains — the disease goitre — was caused by a shortage of iodine, and it could be removed simply by putting iodine back into the food.

Soil of the region poor in iodine → crops and water of the region poor in iodine → people do not get enough iodine → swelling at the front of the neck (goitre)
Common salt supplemented with iodine (iodised salt) → symptoms visibly reduced

Three things follow from this case:

A deficiency can belong to a whole region, not just to one person, because it starts in the soil.
Iodised salt is simply common salt mixed with required quantities of salts of iodine. That is why the packet says “iodised”.
A very small quantity of a mineral can decide whether a person stays healthy — iodine also helps us perform physical and mental activities.

Did you know? Salt farming is a traditional practice of a tribal community named the Agariyas, who work for eight months in the extreme heat of the Little Rann of Kutch to get salt from seawater.

Q5.

How would you find out more about other food components that protect our body from various diseases?

Answer

By using several honest sources and then checking one against the other:

Study the chart in Fig. 3.5 in your book — it lists the food component, its function, some sources, the deficiency disease and the symptoms, all in one place.
Read the label on packets of food, salt and biscuits, where the nutrients are printed.
Survey your neighbourhood, as Activity 3.4 suggests, and link symptoms you see with the diet of that person — under a teacher's guidance.
Ask the right people — the school teacher, the doctor or the nurse at the health centre, or the ASHA worker in your village.
Look it up in the school library or on reliable websites, and note where each fact came from.

Why more than one source: a single source may be wrong or incomplete. If the chart, the label and the doctor all say that Vitamin C prevents scurvy, you can trust it. That cross-checking is itself a part of the scientific method.

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