vitamins

Question 1

What are vitamins?

Answer 1

Don’t provide energy but some are linked to energy yielding pathways
Needed in small amounts (ug or mg/day or IU)
Can be obtained from diet or synthesised

Question 2

What are vitamins diverse functions?

Answer 2

Coenzymes, hormones, cell signalling, antioxidants, regulators of growth and differentiation

Question 3

What affects the availability and absorption of vitamins?

Answer 3

Properties of food
Preexisting disease
Drugs compete for sites of absorption or kill bacteria

Question 4

What does RDA and NRV mean?

Answer 4

RDA- adequate intake to ensure the requirements of all healthy people at met
NRV- nutrient reference value, %

Question 5

What are fat soluble vitamins?

Answer 5

Vit A, D, E and K

Stored in body fat and liver

Question 6

What are water soluble vitamins?

Answer 6

Vit B and C

Requires steady supply

Question 7

What is Vitamin A?

Answer 7

Retinoids (active form)
Carotenoid pigments in plants are cleaved to yield retinoids
Vit A binds to proteins (opsins) in the cells of the retina to form visual pigments
Vit A is a nuclear modulator of gene expression
~hydrophobic retinoic acid passes through cell membrane
~binds to intracellular receptor
~translocates into nucleus
~associates w DNA to influence transcription/translation
So is important for cell proliferation, differentiation and development

Question 8

What happens if you have a deficiency of Vit A?

Answer 8

Major could cause blindness
Impaired resistance to infection (involved in differentiation and function of lymphocytes and neutrophils)
Mild could cause night blindness (poor sight in low light)
Prolonged/severe- metaplasia and keratinisation of conjunctiva epithelial cells or thickening of cornea (xerophthalmia)

Question 9

What is Vitamin D?

Answer 9

Hormone precursor
~D3- calciol/cholecalciferol
~D2- ercalciol/ergocalciferol
Endogenous synthesis is more important than dietary
~D3- photolysis of 7-dehydrocholesterol in skin
Maintains plasma calcium conc and other hormones
Involved w steroid hormone activating nuclear receptors

Question 10

How is Vit D involved in bone metabolism?

Answer 10

Stimulates intestinal Ca2+ and PO43- absorption and renal Ca reabsorption
Mineralisation is controlled by availability of Ava and PO4
Osteoblasts have receptors for calcitriol
If osteoclast activity/no increases, Ca stores can be mobilised

Question 11

What happens if you have a deficiency of Vit D?

Answer 11

Bone mineralisation fails (rickets/osteomalacia)

Impaired immune function

Question 12

What is Vitamin E?

Answer 12

Anti-oxidant- v active free radical trapping

Inactivates protein kinase C in cell signalling

Question 13

What happens if you have a deficiency of Vit E?

Answer 13

V rare as levels need to be low for a long time- difficult due to fat stores
However fat malabsorption conditions eg. Crohns, may contribute

Question 14

What is Vitamin K?

Answer 14

Co-enzyme in postranslational carboxylation of glutamate to y carboxyl glutamate
Permits binding of proteins to membrane phospholipids (for minerals like Ca can be incorporated)
Vit K dependent proteins involved in blood clotting
Some anticoagulants are Vit K antagonists e.g. warfarin

Question 15

What happens if you have a deficiency of Vit K?

Answer 15

Haemorrhagic disease

~esp. newborns which is why Vit K is given at birth

Question 16

What is Vitamin B1?

Answer 16

Co-enzyme THIAMIN involved in-
~energy yielding pathways (pyruvate/alpha-keto-glutarate dehydrogenases) to p. ATP
~nervous system- p. acetyl choline and myelin
~pentose phosphate pathway- p. NADPH for biosynthesis and ribose sugars for nucleotides
Also-
~catabolises leu, isoleu and val
~regulates nerve chloride channels

p.=produces

Question 17

What happens if you have a deficiency of Vit B1?

Answer 17

Beriberi (peripheral neuritis)

Presents as weakness and stiffness

Question 18

What is Vitamin B2?

Answer 18

Electron carrier RIBOFLAVIN in oxidation/reduction reactions
Bound to enzyme
FAD and FMN oxidising coenzymes accept 2 H atoms

Question 19

What happens if you have a deficiency of Vit B2?

Answer 19

Not too big of a problem
Bacterial synthesis forms B2
Efficient conservation to reuse

Question 20

What is Vitamin B3?

Answer 20

NIACIN
Precursor of coenzymes NAD and NADP
Electron carriers in redox reactions
Synthesised from dietary tryptophan

Question 21

What happens if you have a deficiency of Vit B3?

Answer 21

Rare- Pellegra
~dermatitis
~diarrhoea 
~dementia
~death
Oral presentation- atrophic glossitis

Question 22

What are the other B vitamins?

Answer 22

B5- PANTHOTHENIC ACID
~for RBCs and adrenal gland hormones
Deficiency rare- fatigue, insomnia

B6- PYRIDOXINE
~cofactor in transamination
Deficiency- microcytic anaemia

B9- FOLATE and B12- COBALAMIN
~coenzymes involved in DNA/myelin synthesis
Deficiency- anaemia, neurological damage
Supplements- recom. in pregnancy

Question 23

What is Vitamin C?

Answer 23

Reducing sugar and antioxidant ASCORBIC ACID
~keeps Cu+ instead of Cu2+ for dopamine beta-hydroxylase to synthesise nor/adrenaline
~lysine/proline hydroxylases to mature c. tissue (collagen)
~keeps Fe2+ instead of Fe3+ to increase absorption (Vit C increases iron absorption)

Question 24

What are some oral manifestations?

Answer 24

Face- malar pigmentation (B vits), nasolabial seborrhoea (Vit B2,3,6, iron), lack of colour (malnutrition)

Lips- cheilosis (Vit B2,3,6), angular fissures (Vit B2,3,6, iron)

Gingivae- spongy, bleeding, redness (Vit C)

Tongue- glossitis (Vit B3,6,9,12, iron), pale, atrophic, smooth/slick (iron, folate), magenta (riboflavin)