Vitamins: Organic substances which are essential in a small amount to regulate the metabolism and maintain the immune system are called vitamins.

Importance of vitamin A/Function of vitamin A:

Vitamin A was the first fat-soluble vitamin identified in 1913). It performs the following functions.

1. Vitamin A combines with a protein called opsin to form rhodopsin in the rod cells of the retina of the eye. When vitamin A is inadequate, the lack of rhodopsin makes it difficult to see in dim light.
2. It is involved in normal cell differentiation, a process through which embryonic cells transform into mature cells with highly specific functions.
3. Vitamin A supports male and female reproductive processes and bone growth. iv. It is essential for immune function and vitamin-A deficiency causes decreased resistance to infections.
4. It is essential for immune function and vitamin-A deficiency causes decreased resistance to infections.

Importance of vitamin C/Function of vitamin C (Ascorbic Acid):

1. Vitamin C participates in many reactions by donating electrons, essential to the activity of many enzymes. Collagen: Vitamin C is needed to form collagen (a fibrous protein) that gives strength to connective tissues. Collagen is also needed for the healing of wounds.
2. Vitamin C in white blood cells enables the immune system to function properly.

Importance of vitamin D/Function of vitamin D:

1. The best-known function of vitamin D is to help regulate blood levels of calcium and phosphorous
2. Vitamin D increases absorption of these minerals from the intestine and their deposition in bones.