ChemistryISC Class 12 · Biomolecules

Vitamins and Deficiency Diseases: ISC Class 12 Biomolecules

Updated 15 October 2026 · Fact-checked

Vitamins are organic compounds needed in small amounts in the diet for normal growth and health. Vitamins A, D, E and K are fat soluble and stored in the liver and fat tissue; the B group and C are water soluble, excreted in urine and needed regularly (B₁₂ excepted). Each deficiency causes a specific disease, such as scurvy.

Fat-soluble vitamins (A, D, E, K) are stored in the body; water-soluble ones (B group, C) are excreted, and each lack causes a specific disease.

Illustration drawn for QuestionBuddy.

Understand Vitamins and Deficiency Diseases

What vitamins are. Vitamins are organic compounds required in the diet in small amounts to perform specific biological functions for normal growth, maintenance and health. Most cannot be made in the body in sufficient amounts. They are named by letters (A, B, C, D, E, K), and the B vitamins by sub-numbers (B₁, B₂, B₆, B₁₂). The original name 'vitamine' came from 'vital amine', because the first ones found contained amino groups; most do not, so the final 'e' was dropped. Excess of vitamins is also harmful, so vitamin pills should not be taken without a doctor's advice. (CISCE does not require chemical names beyond common ones, or structures.)

Classification by solubility.
Fat-soluble vitamins: A, D, E and K. They dissolve in fats and oils but not in water, and are stored in the liver and adipose (fat-storing) tissue. Because they accumulate, a deficiency develops slowly, and an overdose can build up to harmful levels.
Water-soluble vitamins: the B group and C. They are readily excreted in urine and cannot be stored (except vitamin B₁₂), so they must be supplied regularly in the diet.

Sources and deficiency diseases (NCERT Table 10.3).
• Vitamin A — fish liver oil, carrots, butter, milk. Deficiency: xerophthalmia (hardening of the cornea) and night blindness.
• Vitamin B₁ (thiamine) — yeast, milk, green vegetables, cereals. Deficiency: beriberi (loss of appetite, retarded growth).
• Vitamin B₂ (riboflavin) — milk, egg white, liver, kidney. Deficiency: cheilosis (fissuring at the corners of the mouth and lips), digestive disorders, burning sensation of the skin.
• Vitamin B₆ (pyridoxine) — yeast, milk, egg yolk, cereals, grams. Deficiency: convulsions.
• Vitamin B₁₂ — meat, fish, egg, curd. Deficiency: pernicious anaemia (RBCs deficient in haemoglobin).
• Vitamin C (ascorbic acid) — citrus fruits, amla, green leafy vegetables. Deficiency: scurvy (bleeding gums).
• Vitamin D — exposure to sunlight, fish, egg yolk. Deficiency: rickets (bone deformities in children) and osteomalacia (soft bones and joint pain in adults).
• Vitamin E — vegetable oils such as wheat germ oil and sunflower oil. Deficiency: increased fragility of RBCs and muscular weakness.
• Vitamin K — green leafy vegetables. Deficiency: increased blood clotting time.

Reading a case. Exam questions usually describe a person and their symptoms or diet. Match the symptom to the vitamin, say whether it is fat or water soluble, name a source, and (if asked) explain storage. For example, bleeding gums point to vitamin C (water soluble, citrus fruits and amla), and bone pain in an adult who rarely goes out points to vitamin D (made in the skin in sunlight).

Vitamins and Deficiency Diseases: formulas and key facts

Fat-soluble vitamins: $A, D, E, K$; Stored in liver and adipose tissue; excess can accumulate.
Water-soluble vitamins: $B group, C$; Excreted in urine; needed regularly; B₁₂ is the exception (stored).
Eye and blood vitamins: $A \to night blindness, xerophthalmia; K \to clotting; B_{12} \to pernicious anaemia$; Common one-mark matches.
Bone and gum vitamins: $D \to rickets, osteomalacia; C \to scurvy$; Sunlight and citrus fruits.
Other B vitamins: $B_{1} \to beriberi; B_{2} \to cheilosis; B_{6} \to convulsions$; E → fragile RBCs, muscular weakness.

How to solve Vitamins and Deficiency Diseases questions

Vitamin questions in ISC are short recall and case-based items. Use a three-column table in your head: vitamin, source, deficiency.

1Identify the key symptom (bleeding gums, night blindness, bone deformity, slow clotting, anaemia, convulsions, cracked lip corners).
2Match it to the vitamin and name the disease (scurvy, xerophthalmia/night blindness, rickets/osteomalacia, increased clotting time, pernicious anaemia, convulsions, cheilosis).
3Classify the vitamin as fat or water soluble.
4Suggest a food source (or sunlight for vitamin D).
5For 'why regularly' questions, say water-soluble vitamins are excreted in urine and not stored (except B₁₂).
6Answer with one vitamin only when one is asked; extra choices cost marks.

Vitamins and Deficiency Diseases in real life

Each concept, met in an everyday situation. Read the situation, try the problem, then check the solution. The one-line hook is what to remember.

Vitamin K and blood clotting

Suppose a hospital routinely gives newborn babies a small dose of vitamin K soon after birth. A trainee nurse asks why, and why a single dose is enough for some time when a vitamin such as C must be eaten every day.

Explain the purpose of the dose, the effect of deficiency, and why one dose of this vitamin lasts longer than a dose of vitamin C.

Try it first, then show the solutionSolution

Vitamin K is needed for normal blood clotting; its deficiency increases blood clotting time, so bleeding is harder to stop.
Its dietary source is mainly green leafy vegetables, which a newborn does not eat, so a dose is given.
Vitamin K is fat soluble: it is stored in the liver and fat tissue and released slowly.
Vitamin C is water soluble: excess is excreted in urine and is not stored, so it must be taken regularly.

Answer: Vitamin K prevents prolonged clotting time (bleeding). Being fat soluble it is stored, so one dose lasts; water-soluble vitamin C is excreted and must be eaten regularly.

Memory hook: K for Koagulation (clotting), and fat-soluble vitamins wait in storage.

Tricks to remember Vitamins and Deficiency Diseases

Short memory aids. Say each one aloud once, then use it on a question the same day.

ADEK in the fat
Fat-soluble vitamins spell ADEK (A, D, E, K). Everything else (B group, C) is water soluble.
Use it when: Classification questions.
Body map
Eyes: A. Gums: C. Bones: D. Blood clotting: K. Blood cells: B₁₂ (anaemia) and E (fragile RBCs). Nerves (convulsions): B₆. Lips: B₂. Appetite/growth (beriberi): B₁.
Use it when: Symptom-to-vitamin matching.
Twelve is the odd one out
All water-soluble vitamins wash out in urine, except B₁₂, which is stored.
Use it when: Storage questions and assertion-reason items.

Vitamins and Deficiency Diseases: solved examples

Ordered from board level to HOTS. Try each one before you open the solution.

Example 1: Slow clotting · 1 mark · MCQBoard level

Deficiency of which vitamin increases blood clotting time?
(a) vitamin A
(b) vitamin C
(c) vitamin E
(d) vitamin K

Try it first, then show the solutionSolution

Vitamin K is needed for normal clotting of blood.
Its deficiency increases clotting time.

Answer: (d) vitamin K.

Example 2: Fat or water soluble · 2 marks · Short answerBoard level

Classify vitamins A, B₁, C, D, E and K as fat soluble or water soluble. Why must water-soluble vitamins be taken regularly in the diet?

Try it first, then show the solutionSolution

Fat soluble: A, D, E, K. Water soluble: B₁, C (1 mark).
Water-soluble vitamins are readily excreted in urine and cannot be stored in the body (except B₁₂), so they must be supplied regularly (1 mark).

Answer: A, D, E, K fat soluble; B₁, C water soluble; water-soluble vitamins are excreted and not stored.

Example 3: Three B vitamins · 3 marks · Short answerHarder board level

Name the vitamin whose deficiency causes each of the following, and give one source of each: (a) fissuring at the corners of the mouth and lips; (b) convulsions; (c) red blood cells deficient in haemoglobin.

Try it first, then show the solutionSolution

(a) Cheilosis: vitamin B₂ (riboflavin); milk, egg white, liver or kidney (1 mark).
(b) Convulsions: vitamin B₆ (pyridoxine); yeast, milk, egg yolk, cereals or grams (1 mark).
(c) Pernicious anaemia: vitamin B₁₂; meat, fish, egg or curd (1 mark).

Answer: (a) B₂ (riboflavin). (b) B₆ (pyridoxine). (c) B₁₂.

Example 4: Why excess can harm · 3 marks · Short answerHarder board level

A friend takes high-dose vitamin A and vitamin D tablets daily 'to be extra healthy'. Explain why this can be harmful, while taking extra vitamin C is less likely to build up in the body. Which water-soluble vitamin is an exception, and why?

Try it first, then show the solutionSolution

Vitamins A and D are fat soluble and are stored in the liver and adipose tissue, so repeated excess doses accumulate to harmful levels (1 mark).
Vitamin C is water soluble; excess is excreted in urine and does not build up (1 mark).
Vitamin B₁₂ is water soluble but is stored in the body, unlike the rest of the B group and C (1 mark).

Answer: Fat-soluble A and D accumulate; water-soluble C is excreted; B₁₂ is the stored exception. Vitamin pills should be taken only on medical advice.

Example 5: Diet analysis · 5 marks · Long answerHOTS / competency

Suppose a young adult follows a strict plant-only diet (no meat, fish, eggs or dairy), works night shifts and sleeps by day, and eats almost no green leafy vegetables.
(a) Which three vitamin deficiencies is this person most at risk of? Give the reason for each from the diet or lifestyle. [3]
(b) Name the deficiency disease or symptom for each. [1]
(c) For one of the three, explain why the body can tolerate a short gap in intake before symptoms appear. [1]

Try it first, then show the solutionSolution

(a) Vitamin B₁₂: its sources are meat, fish, egg and curd, all absent (1 mark).
Vitamin D: little exposure to sunlight, and no fish or egg yolk (1 mark).
Vitamin K: its source is green leafy vegetables, which are hardly eaten (1 mark).
(b) B₁₂: pernicious anaemia; D: osteomalacia (soft bones, joint pain); K: increased blood clotting time (1 mark).
(c) Vitamin D (or K) is fat soluble and stored in the liver and fat tissue; B₁₂ is also stored. Stored reserves delay the appearance of symptoms (1 mark).

Answer: (a) B₁₂, D and K. (b) Pernicious anaemia, osteomalacia, increased clotting time. (c) These vitamins are stored, so reserves last for a while.

Where students lose marks in Vitamins and Deficiency Diseases

The slips examiners see most often, and what to write instead.

Mistake: Naming the wrong vitamin for rickets
ISC examiners reported vitamin A or B given instead of vitamin D for rickets and joint pain (2024).
Do this: Bones: vitamin D (rickets in children, osteomalacia in adults).
Usually costs: 1 mark.
Mistake: Writing more than one vitamin
Examiners noted 'vitamin B' or more than one vitamin written for bleeding gums (2025).
Do this: Bleeding gums: vitamin C only. Give a single, specific answer.
Usually costs: 1 mark.
Mistake: Mixing up fat- and water-soluble groups
Students put vitamin C with the fat-soluble group or K with the water-soluble group.
Do this: Fat soluble: A, D, E, K. Water soluble: B group and C.
Usually costs: ½ to 1 mark.
Mistake: Using vague disease names
Students write 'weak bones' or 'blood disease' instead of the named condition.
Do this: Use the exact terms: scurvy, rickets, osteomalacia, beriberi, xerophthalmia, pernicious anaemia, cheilosis.
Usually costs: ½ mark each.

Exam tips

Learn Table 10.3 as a grid: vitamin, source, deficiency; ISC asks one cell at a time.
In case questions, quote the symptom given and link it to the vitamin explicitly.
When asked why a vitamin must be eaten regularly, mention excretion in urine and lack of storage.
Chemical names and structures of vitamins are not required by CISCE; common names (thiamine, riboflavin, pyridoxine, ascorbic acid) are enough.
Mention sunlight as a source of vitamin D; it often earns the mark.

Practice questions on Vitamins and Deficiency Diseases

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

Q1 · 1 mark · MCQBoard level
Scurvy is caused by deficiency of:
(a) vitamin B₁
(b) vitamin C
(c) vitamin D
(d) vitamin K
Hint
Bleeding gums.
Answer
(b) vitamin C (ascorbic acid).
Q2 · 2 marks · Short answerBoard level
What are vitamins? Why was the term 'vitamine' changed to 'vitamin'?
Hint
Vital + amine.
Answer
Organic compounds required in small amounts in the diet for specific biological functions, normal growth and health. 'Vitamine' (vital amine) was coined because early ones contained amino groups; most do not, so the 'e' was dropped.
Q3 · 2 marks · Short answerHarder board level
A child cannot see well in dim light, and the cornea of the eye is becoming hard. Name the vitamin lacking, the two conditions, and two good sources.
Hint
Think of carrots.
Answer
Vitamin A. Night blindness and xerophthalmia (hardening of the cornea). Sources: fish liver oil, carrots, butter, milk (any two).
Q4 · 3 marks · Short answerHarder board level
Distinguish between rickets and osteomalacia. Name the vitamin involved and explain why people who spend most of their time indoors are at greater risk.
Hint
Children versus adults.
Answer
Rickets: bone deformities in children. Osteomalacia: soft bones and joint pain in adults. Both are due to vitamin D deficiency. Exposure to sunlight is a main source of vitamin D, so people who stay indoors get less.
Q5 · 1 mark · Assertion-reasonHarder board level
Assertion (A): Vitamin B₁₂ need not be taken every day, although it is a water-soluble vitamin.
Reason (R): Vitamin B₁₂ is a fat-soluble vitamin.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Hint
B₁₂ is water soluble but stored.
Answer
(c). A is true because B₁₂ is stored in the body; R is false because B₁₂ is water soluble.
Q6 · 3 marks · Short answerHarder board level
Identify the vitamin from each description: (a) found in wheat germ and sunflower oil; deficiency makes RBCs fragile and muscles weak. (b) found in yeast, milk, green vegetables and cereals; deficiency causes loss of appetite and retarded growth. (c) found in citrus fruits and amla; deficiency causes bleeding gums.
Hint
One fat soluble, two water soluble.
Answer
(a) Vitamin E. (b) Vitamin B₁ (thiamine), beriberi. (c) Vitamin C (ascorbic acid), scurvy.
Q7 · 3 marks · Short answerHOTS / competency
Why should vitamin supplements not be taken without a doctor's advice? Use the classification of vitamins in your answer.
Hint
Think about storage.
Answer
Excess vitamins are harmful. Fat-soluble vitamins (A, D, E, K) are stored in the liver and fat tissue, so excess doses accumulate and can become toxic. A doctor can judge which vitamin is actually lacking and the right dose; taking the wrong vitamin also leaves the real deficiency untreated.
Q8 · 3 marks · Case-basedHOTS / competency
Read and answer.
Suppose a hostel cook boils green vegetables for a long time in plenty of water and then throws the water away. After some weeks, several students complain of bleeding gums and slow healing of small cuts.
(i) Which vitamin are the students probably lacking? Name the disease. [1]
(ii) Why does the cooking method reduce this vitamin in the food? [1]
(iii) Suggest one change in cooking and one food to add. [1]
Hint
Which vitamins dissolve in water?
Answer
(i) Vitamin C; scurvy. (ii) Vitamin C is water soluble, so it dissolves into the cooking water that is thrown away (and long heating destroys some of it). (iii) Cook vegetables briefly in less water (or use the water in soups); add citrus fruits or amla.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1.Which vitamins are fat soluble?Show answer
A, D, E and K.
2.Deficiency disease of vitamin B₁?Show answer
Beriberi.
3.Which water-soluble vitamin is stored in the body?Show answer
Vitamin B₁₂.
4.Deficiency of vitamin B₂ causes?Show answer
Cheilosis, digestive disorders and burning sensation of the skin.
5.Source of vitamin E?Show answer
Vegetable oils such as wheat germ oil and sunflower oil.
6.Deficiency of vitamin A causes?Show answer
Night blindness and xerophthalmia.

Vitamins and Deficiency Diseases: frequently asked questions

What is the difference between fat-soluble and water-soluble vitamins?

Fat-soluble vitamins (A, D, E, K) dissolve in fats and are stored in the liver and fat tissue; water-soluble vitamins (B group, C) dissolve in water, are excreted in urine and must be taken regularly (B₁₂ is stored).

Which vitamin deficiency causes bleeding gums?

Vitamin C (ascorbic acid); the disease is scurvy.

Can too many vitamins be harmful?

Yes. Excess of vitamins, especially the stored fat-soluble ones, is harmful, so supplements should be taken only on medical advice.

Why is vitamin D called the sunshine vitamin?

Exposure of the skin to sunlight is a main source of vitamin D.

Are structures of vitamins required for ISC?

No. The CISCE syllabus asks for classification (fat or water soluble) and deficiency diseases; chemical names and structures are not required.