describe the general role n defence simplons of vitamin A,D,E,K,
Answers
Answer:
Small amounts of vitamins are required in the diet to promote growth, reproduction, and health. Vitamins A, D, E, and K are called the fat-soluble vitamins, because they are soluble in organic solvents and are absorbed and transported in a manner similar to that of fats.
Explanation:
Vitamin D
The active form of vitamin D promotes intestinal absorption of calcium and phosphorus and influences bone mineralization. Vitamin D occurs in two forms that are equally well utilized in the body. Vitamin D2 (ergocalciferol) is produced commercially by ultraviolet (UV) irradiation of the plant sterol ergosterol; vitamin D3 (cholecalciferol) is formed by the action of sunlight on the precursor 7-dehydrocholesterol in the skin. The human body utilizes both forms of vitamin D by hydroxylating first the 25-position in the liver and then the 1α-position in the kidney, producing the biologically active 1α,25-dihydroxycalciferols.
Vitamin E
Vitamin E is an important antioxidant that is thought to protect polyunsaturated fatty acids from oxidative destruction in cell membranes. Vitamin E activity in foods is due to the presence of tocopherols and tocotrienols—compounds of plant origin. The most important of these is α-tocopherol; less active are β-tocopherol, γ-tocopherol, and α-tocotrienol. Vegetable oils are the richest source of vitamin E. Other good sources include nuts, seeds, whole grains, and wheat germ. The vitamin E content of animal foods is generally low.
Vitamin K
Vitamin K is needed in the liver for formation of several blood clotting factors. Vitamin K1, (phylloquinone) is synthesized by plants, whereas vitamin K2 homologs (menoquinones) are synthesized by bacteria. The human body can obtain vitamin K from dietary sources as well as through synthesis by the gut microflora.