Nutrition Flashcards
(234 cards)
Where are vitamins supplied from?
Diet, some can be synthesised (D - sun. B&K -gut bacteria)
What type of compounds are vitamins?
Organic
What type of functions do they have?
Co-enzymes, hormones, cell signalling, antioxidants, regulators of growth & differentiation
What can affect absorption of vitamins?
Properties of the food e.g. low in fat
pre-existing disease e.g. ceiliac - impaired fat absorption and gastritis (low acid- b12)
Drugs may compete for absorption and kill bacteria
What is RDA?
recommended daily allowance - an intake that is adequate to ensure the requirements of all health people are met
Which vitamins are fat soluble and which are water soluble?
Fat soluble: Vitamin A Vitamin D Vitamin E Vitamin K
Water soluble:
B vitamins
Vitamin C
What type of vitamins can be stored?
Fat soluble stored. water soluble not stored
What is the active form of vitamin A?
Retinoids
What pigments give retinoids?
Carotenoid pigments (e.g. B carotene)
What is the function of vitamin A?
binds to proteins (opsin) in the cells of the retina to form visual pigments
Nuclear modulator of gene expression:
Cell proliferation
Differentiation
(especially epithelia)
Development
What are the symptoms of a vitamin A deficiency?
Major cause of blindness in children under 5 in developing countries
impaired resistance to infection - differentiation and function of lymphocytes and neutrophils affected
mild deficiency = night blindness
severe deficiency = metaplasia and keratinisation of the conjuctiva epithelial cells and thickening of the cornea (xerophthalmia)
What process produces vitamin D endogenously?
(D3 -photolysis of 7-dehydrocholesterol)
What are the functions of vitamin D?
Maintenance of plasma Calcium concentration (along with parathyroid hormone and calcitonin)
Steroid hormone activating nuclear receptors and influencing > 50 genes
What is cholecalciferol?
Vitamin D3 which is made by the skin when exposed to sunlight
What is egocalciferol?
also known as vitamin D2 and calciferol, is a type of fat soluble vitamin D found in food and used as a dietary supplement
What is the role of vitamin D in bone metabolism?
- Vit D stimulates intestinal Calcium and phosphate absorption and renal Ca reabsorption - mineralisation of bone is controlled by the availabiliy of Ca and PO4
Osteoblasts have receptors for calcitriol (active metabolite of vitamin D)
Osteoclast activity/number (paradoxically) increased
= Promotes formation and mineralisation of bone
What condition is caused by Vit D deficiency?
Rickets and osteomalacia (the softening of the bones caused by impaired bone metabolism primarily due to inadequate levels of available phosphate, calcium, and vitamin D)
What is vitamin E?
Lipid soluble antioxidant - very active free radical trapping
What does vitamin E do?
Free radical trapping
Cell signalling (inactivates protein kinase C)
deficiency not normally a problem
What does vitamin K do?
Co-enzyme in postranslational carboxylation of glutamate to γ carboxy glutamate (gla)
Permits binding of proteins to membrane phospholipids
Klotting: vitamin K dependent proteins involved in blood coagulation (thrombin factors VII, IX and X, protein C, S, Z)
What are vitamin K antagonists?
Anticoagulants e.g. warfarin
What can vitamin K deficiency lead to?
Haemorrhagic disease
Name some of the B vitamins
Thiamin (B1), ribofavin (B2), Niacin (B3), B6, Folic acid (B9), B12, pantothenic acid (B5)
What are all B vitamins?
Co-enzymes (co-factors)