vitamin A Flashcards
what are the forms of vitamin A
-retinol: easily absorbed. stored in the liver
-beta-carotene: not easily absorbed. converted to retinol in the lining of the intestine
what are the properties of retinol
-a yellow-fat soluble alcohol/ insoluble in water
-soluble in organic solvents, e.g. acetone
-heat stable, but affected by prolonged high temperatures
-destroyed by oxygen
what are the sources of retinol
-offal -butter
-milk -eggs
what are the properties of beta-carotene
-a yellow or orange fat-soluble oil/insoluble in water
-soluble in fat solvents, e.g. alcohol
-heat stable, but affected by prolonged high temperatures
-unaffected by oxygen
-ability to counteract the damaging effects of free radicals
what are the sources of beta-carotene
-carrots -sweet potatoes
-tomatoes -red peppers
what are the biological functions of vitamin A
-required to manufacture the pigment rhodopsin found in the retina, which helps the eye to adapt to dim light
-helps maintain healthy skin and the mucous membrane, e.g. the eyes
-aids growth and development of children
- beta-carotene acts as a powerful antioxidant that can counteract the damaging effects of free radicals
what are the effects of deficiency of vitamin A
-night blindness, in which a person will struggle to see dim light due to lack of rhodopsin
-follicular hyperkeratosis, a condition that results in rough, dry skin and inflamed hair follicles
- xerophthalmia can occur on the surface of the eye due to lack of mucous. this causes eyes to dry out and become infected with bacteria which will lead to blindness
-stunted or delayed growth in children
-risk of damage to cells by free radicals, increasing the risk of some cancers. coronary heart disease and strokes
what is the RDA of vitamin A
children: 400-500
teens and adults: 600-700
pregnancy: 700
lactation: 950
