Vitamins - Water Soluble and Fat Soluble Flashcards
What are vitamins?
Organic compounds with essential biochemical functions that are not made by the body
What are the water soluble vitamins?
thiamin (B1), riboflavin (B2), niacin (B3), pyridoxine (B6), pantothenic acid, biotin, folate, cobalamin (B12), and vitamin C (ascorbic acid)
What are the fat soluble vitamins?
A, D, E, and K
Vitamin deficiencies are
rare in healthy individuals on well-balanced diets
Vitamin deficiencies are important to consider
for unusual diets, during growth, in disease, and in developing countries
Fat soluble vitamin digestion is compromised by
pancreatic insufficiency or bile blockage
Water soluble vitamins are taken up by
the intestine
Vitamin K has no RDI because
it is made by gut flora
PLP
pyridoxal phosphate (B6)
NAD
niacin (B3)
CoA
Pantothenic acid
FMN, FAD
riboflavin (B2)
THF
folate
Thiamin (B1) is critical for
decarboxylations; carbohydrate, protein, and fat metabolism; nerve function
Deficiency of thiamin (B1) causes
beriberi (polished rice); Wernicke-Korsakoff (alcoholics)
Sources of thiamin (B1) include
vegemite, wholemeal breads, fortified cereals
Thiamin (B1) is a component of which enzyme?
Pyruvate dehydrogenase
Why is thiamin (B1) critical to nerve function?
It links anaerobic and aerobic metabolism (on which nerves rely) by pyruvate dehydrogenase
What is the role of riboflavin (B2)?
electron carrier - flavin mononucleotide (FMN), flavin adenine dinucleotide (FAD); carb, protein, and fat metabolism
Sources of riboflavin (B2) include
vegemite, milk, cheese, fortified cereals
Deficiency of riboflavin (B2)
is rare, usually only seen in chronic alcoholics with other deficiencies
What is the role of niacin (B3)?
coenzyme; electron carrier (NADH, NADPH); carb, protein, and fat metabolism
Sources of niacin (B3)
Vegemite, wheat bran, fortified cereals
Niacin (B3) deficiency
seen in alcoholics; Pellagra (dermatitis, diarrhoea, dementia, death)
Sources of pyridoxine (B6)
Vegemite, nuts, bananas, fortified cereals
Role of pyridoxine (B6)
amino acid metabolism (transamination)
Deficiency of pyridoxine (B6)
rare; need varies with protein intake; linked to original contraceptive pill in 60s
What is the role of biotin?
carboxylation in proteins (eg Acetyl-coA carboxylase to produce Malonyl-CoA); glucose, fat, amino acid biosynthesis
Sources of biotin include
brewer’s yeast, cooked egg yolk (raw has avidin, antagonist of biotin); soy beans
Deficiency of biotin
caused by avidin in raw eggs, results in scaly, shiny, dry skin
What is the role of folate?
critical in DNA synthesis
Sources of folate include
green vegetables, liver, fortified cereals
Deficiency of folate
occurs commonly in elderly and chronic alcoholics; causes spina bifida if in pregnancy; causes macrocytic anaemia and glossitis (pillae die on tongue)
RDI for folate is
400ug/day (previously 120ug/day)
Folate supplementation may be linked to
increased rates of cancer due to its role in DNA synthesis
What is the role of cobalamin (B12)?
coenzyme containing cobalt; folate metabolism in DNA synthesis; transalkylations in nerves and blood
Sources of cobalamin (B12)
Meat, egg yolks, cheese
Deficiency of cobalamin (B12)
common in vegans and IF deficiency (genetic or autoimmune); causes pernicious anaemia with yellowish skin and faint icterus of sclerae due to bilirubin, lightening of hair and irises; peripheral neuritis
Intrinsic factor
glycoprotein produced by parietal cells of stomach necessary for B12 absorption; genetic or autoimmine deficiencies tx with B12 injections
What is the role of vitamin C?
cofactor in collagen synthesis (proline hydroxylase adding -OHs to prolines on outside of collagen that allow it to H-bond and give it strength); neurotransmitter metabolism; iron absorption; antioxidant
Sources of vitamin C
citrus fruit, cabbage
Deficiency of vitamin C
scurvy
What is the role of vitamin A?
half of B-carotene; produces retinal (night vision) and retinol (epithelium growth in skin and eyes)
Sources of vitamin A
B-carotene (coloured vegetables)
Vitamin A deficiency
xeropthalmia (dry eye) caused by retinol deficiency can lead to blindness if not treated
What is the role of vitamin D?
Ca2+ regulation and bone development - facilitates uptake of Ca2+ in gut which prevents it being absorbed from bones; mediates protection against infection, cancer, and autoimmune disease
Sources of vitamin D include
derived from cholesterol and synthesized with UV light and hydroxylations in liver and kidney to form calcitriol (hormone)
Deficiency of vitamin D
rickets in children (knock knees and bow legs); osteomalacia in adults (Ca taken from bones if can’t get it from gut)
Vitamin D status is assessed by measuring
25OH-D; <25nmol/L = deficiency
What is the role of vitamin E?
antioxidant in membranes to accept free radicals; linked to signalling in inflammation and cell division
Sources of vitamin E include
high levels in seed oils
What is the role of vitamin K?
important in blood clotting - essential for the gamma-glutamyl carboxylase that adds a carboxyl group to glutamic acid eresidues on II, VII, IX, and X to activate them
Vitamin K deficiency
inadequate clotting and haemorrhage
