Proteins, Vitamins and Nucleic Acids — Part 2: Vitamins and nucleic acids: visual lesson, ISC Class 12 Chemistry

Lesson

Small needs, big effects

Part 2 — vitamins, needed in tiny amounts, and the nucleic acids that carry the instructions for every protein.

In this lesson you will

Classify vitamins A, B, C, D, E and K as fat-soluble or water-soluble
Match each vitamin with its main function and deficiency disease
Name the purine and pyrimidine bases and describe the DNA double helix
Compare DNA and RNA in sugar, bases, structure and function

Concept

Vitamins: fat-soluble and water-soluble

Vitamins are organic compounds needed in small amounts in the diet for normal growth and health; most cannot be made in the body. Fat-soluble: A, D, E, K — stored in the liver and fatty tissue, so large excesses can be harmful. Water-soluble: B group and C — not stored (excess is excreted in urine), so they must be supplied regularly; they are also easily lost when vegetables are boiled and the water discarded. (Vitamin B₁₂ is an exception: it is stored in the liver.)

Table comparing fat-soluble and water-soluble vitamins by members, storage and supply
Group	Vitamins	Storage	Supply
Fat-soluble	A, D, E, K	Liver and fatty tissue	Excess can accumulate
Water-soluble	B group, C	Not stored (except B₁₂)	Needed regularly

Concept

Functions and deficiency diseases

Each vitamin has characteristic sources and a characteristic deficiency disease.

Table of vitamins A, B1, B2, B6, B12, C, D, E and K with sources and deficiency diseases
Vitamin	Good sources	Deficiency disease or symptom
A	Carrots, fish-liver oil, milk	Night blindness, xerophthalmia (hardening of cornea)
B₁	Whole cereals, yeast, milk	Beriberi (loss of appetite, retarded growth)
B₂	Milk, egg white, liver	Cheilosis (cracked lips), digestive disorders
B₆	Yeast, cereals, egg yolk	Convulsions
B₁₂	Meat, fish, eggs, curd	Pernicious anaemia
C	Citrus fruits, amla, green leafy vegetables	Scurvy (bleeding gums)
D	Sunlight on skin, fish, egg yolk	Rickets in children, osteomalacia in adults
E	Vegetable oils, sunflower seeds	Fragile red blood cells, muscular weakness
K	Green leafy vegetables	Increased blood-clotting time

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