Fat Soluble Vitamins Flashcards
What are vitamins?
Vitamins are organic nutrients required in small quantities in the diet. They can not be synthesized in the body.
They are involved in metabolic processes in the human body.
List the fat soluble vitamins
Vit A (retinol)
Vit D (cholecalciferol. It is derived from cholesterol)
Vit E (tocopherol)
Vit K
Describe the chemical of vitamin A
It exists in 3 forms retinol, retinadehyde and retinoic acid. It is made up a six membered ring( trimethy cyclohexenyl) to which is attached an unsaturated hydrocarbon chain( isoprenoid chain) with the following functional groups( CHO, COOH, CH2OH)
Describe the metabolic role of vitamin A
It is important in vision. It is found in the cones and the rods which are located in the retina.
i) Cones: in the cones, the retinol combines with opsin to form iodopsin which are specialized in color and detailed vision. Cones are responsible for vision during the day.
ii) Rods : in the rods, the retinol combines opsin with to form rhodopsin which is responsible for visual acuity in dim light. Rods are responsible for night vision.
State the recommended daily requirements and sources of vitamin A
Recommended Daily requirements.
- 5000 IU/day.
Sources
I) Animal source: Liver oil, butter, milk and eggs.
II) Plant source: in the form of B carotene in dark green vegetable, tomatoes, yellow vegetables, carrots, fruits like mangoes and papaya
Describe the clinical feature due to deficiency of vitamin A
Deficiency cause xerophthalmia which the keratinization of the cornea causing blindness. It also causes night blindness and dryness of the skin
Describe the metabolic role of vitamin D
It plays are vital role in the absorption of calcium and phosphates from the GIT. It also plays a role in the mineralization of bones. It is also known as a pro hormone. Its mechanism of action is similar to steroid hormones. It causes the synthesis of calcium binding proteins
State the recommended daily requirements and the sources of vitamin D
Recommended Daily requirements.
100 IU.
Sources
The major source is synthesis from 7- dehydro cholesterol in the skin through the action of UV light . Only when the sun light exposure source is inadequate is the dietary source is required. Dietary source is mainly from animal source.
Dietay source: fish liver oils ,milk, butter cheese and eggs
Describe the clinical feature due to deficiency of vitamin D
It causes rickets in children due to under mineralization and osteomalacia in adults
Describe the chemical structure of vitamin E
It exists in the form of tocopherols. And there are 4 types namely, alpha, beta, gamma and delta tocopherols. There are 2 fused 6 membered rings to which is attached a hydrocarbon chain. One of the rings is a benzene ring
Describe the metabolic role of vitamin E
It is important as an anti oxidant. It removes free radicals and protects the peroxidation of unsaturated fatty acids in the cell membrane, hence it maintains the integrity of cell membranes
State the recommended daily requirements and the sources of vitamin E
Recommended daily requirements:
10-20 IU/day
Sources
I) Animal source: fish liver oils ,milk, butter cheese and eggs.
II)Plant source: Vegetable oils( corn oil, sunflower oil,wheat gem oil,) peanuts, vegetables( lettuce, cabbage.)
Describe the clinical feature due to deficiency of vitamin E
Leads to hemolytic anemia
Describe the chemical structure of vitamin K
It is made up of 2 fused 6 membered rings( 2 methyl,3OH, 1,4 napthoquinononone) to which is attached a hydrocarbon chain
List the types of vitamin K
There are 3 types namely:
-K1- phylloquinone- found in plants.
-K2- menaquinone- synthesized in the gut from bacteria.
- K3- menadione- the synthetic form. It does not have the hydrocarbon chain. It is three times more effective than the other 2 types
