Answer 1

1. Vitamins occur in plants, animals as well as microorganisms, i.e. it has widespread occurrence.
2. The plants and many microbes can synthesize all the vitamins, whereas only a few vitamins are synthesized in animals.
3. Human body can synthesize some vitamins. For eg. Vitamin A from precursor carotene and Vitamin D from ultraviolet irradiation of 7-dehydrocholesterol.  Some members of Vitamin B- complex are synthesized by micro-organisms present in the intestinal tract. Vitamin C is also synthesized in some animals such as rat.
4. All the cells of the body store vitamins to some extent.
5. Vitamins are partly destroyed and partly excreted.
6. Vitamins are non-antigenic.
7. Most of the vitamins are coenzymes, however few are haematopoietic.
8. Vitamins carry out functions in very low concentration; hence total daily requirement is very small.
9. Vitamins are effective when taken orally.
10. A lack of one or more vitamins (avitaminosis) leads to characteristic deficiency symptoms in humans as well as in animals.