Introduction
A Vitamins is an organic molecule which is required by a living organism in minute amounts for proper health. An organism deprived of all sources of a particular vitamin will eventually suffer from disease symptoms specific to that vitamin. Vitamins can be classified into two and they are water soluble, which means they dissolve easily in water and fat soluble, which means they are absorbed through the intestinal tract with the help of lipids. A vitamin forms an important nutrient of diet.
Functions: A Vitamins
The functions of a vitamin are as follows:
Vision: The retina is located at the back of the eye. When light passes through the lens, it is sensed by the retina and converted to a nerve impulse for interpretation by the brain. Retinol is transported through A Vitamins to the retina via the circulation, where it moves into retinal pigment epithelial cells.
Regulation of gene expression: Retinoic acid (RA) and its isomers act as hormones to affect gene expression and thereby influence numerous physiological processes. Through the stimulation and inhibition of transcription of specific genes, retinoic acid plays a major role in cellular differentiation, the specialization of cells for highly specific physiological roles. Most of the physiological effects attributed to A Vitamin appear to result from its role in cellular differentiation.
Immunity: A vitamins is commonly known as the anti-infective vitamin, because it is required for normal functioning of the immune system. The skin and mucosal cells (cells that line the airways, digestive tract, and urinary tract) function as a barrier and form the body's first line of defense against infection.
Growth and Development: A vitamins excess and deficiency are known to cause birth defects. Retinol and retinoic acid (RA) are essential for embryonic development
Red blood cell production: Red blood cells, like all blood cells, are derived from precursor cells called stem cells. These stem cells are dependent on retinoids for normal differentiation into red blood cells. Additionally, A vitamins appears to facilitate the mobilization of iron from storage sites to the developing red blood cell for incorporation into hemoglobin, the oxygen carrier in red blood cells
Conclusion
A vitamins is a fat-soluble vitamin which is involved in the formation and maintenance of healthy skin, hair, and mucous membranes. A vitamins also helps us to see in dim light and is necessary for proper bone growth, tooth development, and reproduction.

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