Vitamins

Question 1

Vitamins - why do we need them

Answer 1

Essential for normal body function
Deficiency may cause disease
Needed in small amounts (μg or mg/day)
Do not provide energy
Have to be supplied in diet
Some can be synthesised (D - sun, B and K-gut bacteria)

Question 2

Vitamins structure

Answer 2

Chemically disparate
Organic compounds (trace elements and minerals: inorganic)

Question 3

Vitamins functions

Answer 3

Co-enzymes
Hormones
Cell signalling
Antioxidants
Regulators of growth and differentiation

Question 4

How were vitamins found

Answer 4

Casimir Funk (1884-1967)
Milk contains 'accessory growth factor'
Thought to be an amine
Vita + amine = vitamine
More than one factor in milk
-A (lipid soluble in cream)
-B (water soluble in whey)

Question 5

Biological availability and adsorption

Answer 5

< adsorption can lead to deficiency
Properties of food e.g. low in fat could lead to not having fat soluble vitamins
Pre-existing disease
-e.g. celiac (impaired fat absorbtion)
-gastritis (low acid - B12)
Drugs may compete for absorbtion, kill bacteria

Question 6

Recommended daily allowance

Answer 6

RDA: ‘an intake that is adequate to ensure the requirements of all healthy people are met’
Supplements and toxicity if too much is taken
Requirements may vary: children, pregnancy (folate: crucial role in development of embryos especially spinal cord) - for differentiation, growth etc.

Question 7

Fat soluble vitamins

Answer 7

A, D, E, K

In general fat soluble can be stored, water soluble not

Question 8

Water soluble vitamins

Answer 8

B vitamins, C

In general fat soluble can be stored, water soluble not

Question 9

Vitamin A

Answer 9

Retinoids (active form)
Carotenoid pigments (e.g. β carotene) in plants cleaved to yield retinoids

Question 10

Vitamin A functions

Answer 10

Binds to proteins (opsin) in cells of retina to form visual pigments
Nuclear modulator of gene expression (signalling molecule)
-cell proliferation
-differentiation (especially epithelia)
-development
Lipid soluble, dissolves through cell membrane, binding to RA receptor, goes into nucleus, attaches to DNA, affects transcription

Question 11

Vitamin A deficiency

Answer 11

Major cause of blindness in children under 5 in developing countries
Impaired resistance to infection
-differentiation and function of lymphocytes and neutrophils
Mild deficiency - night blindness
More prolonged/ severe
-metaplasia and keratinisation of the conjunctiva epithelial cells
-thickening of the cornea (xerophthalmia)

Question 12

Vitamin D

Answer 12

Hormone precursor
-vitamin D3 calciol/ cholecalciferol
-vitamin D2 ercalciol/ ergocalciferol
Endogenous synthesis more important than dietary sources 
-D3 - photolysis of 7-dehydrocholesterol

Question 13

Vitamin D functions

Answer 13

Maintenance of plasma calcium conc. (along with parathyroid hormone and calcitonin)
Steroid hormone activating nuclear receptors and influencing >50 genes

Question 14

Bone metabolism

Answer 14

Vit D stimulation of intestinal Ca2+ and PO43- absorption and renal Ca reabsorption
Mineralisation controlled by availability of Ca and PO4 (maintained by vit D)
Osteoblasts have receptors for calcitriol (active metabolite of vit D)
Osteoclast activity/ number (paradoxically) increased
Promotes formation and mineralisation of bone

Question 15

Vitamin D deficiency

Answer 15

Rickets and osteomalacia
Failure of bone mineralisation
Eradication by supplementation in 1950s in ‘developed’ world
1 in 5 people in UK deficient (2016)
Racial genetic predisposition (defect in calcitriol hydrolase: no calcitriol)
Vit D deficient mice have impaired immune function (lymphocytes and monocytes)

Question 16

Vitamin E and function

Answer 16

Lipid soluble antioxidant
Very active free radical trapping
Other effects on cell signalling (inactivates protein kinase C)
Deficiency not normally a problem

Question 17

Vitamin K and function

Answer 17

Co-enzyme in postranslational carboxylation of glutamate to γ carboxy glutamate (gla)
Permits binding of proteins to membrane phospholipids

Question 18

Vitamin K: klotting

Answer 18

Vit K dependent proteins involved in bood coagulation (thrombin, factors VII, IX and X, protein C, S and Z0
Clotting occurs on phospholipid surfaces
Deficiency leads to haemorrhagic disease (newborns particularly at risk)
Some anticoagulants are vitamin K antagonists (disrupting) e.g. warfarin

Question 19

B vitamins examples

Answer 19

Thiamin (B1)
Ribofavin (B2)
Niacin (B3)
B6
Folic acid (B9)
B12
Panthothenic acid (B5)

Question 20

B vitamins functions

Answer 20

All co-enzymes (co-factors)
-‘helper molecules’
-non-proteins but bind to protein (enzymes)
Required for protein’s biological activity

Question 21

Thiamin

Answer 21

Vitamin B1
Co-enzyme in central energy yielding pathways (pyruvate and keto-glutarate dehydrogenase)
These produce ATP (lack of ATP = cell death)
Neurotransmitters, myelin
Pentose phosphate pathway
Co-enzyme in catabolism of leu, isoleu and val
Regulates nerve chloride channels

Question 22

Thiamin pentose phosphate pathway

Answer 22

Co-enzyme

Transketolase: NADPH for biosynthesis and ribose for nucleotides

Question 23

Thiamin deficiency

Answer 23

Berberi-peripheral neuritis: weakness, stiffness

Question 24

Riboflavin

Answer 24

Vitamin B2
E- carriers in variety of oxidation and reduction reactions central to metabolism (mitochondrial e- transport chain)
Remain bound to enzyme
FAD, FMN oxidising coenzymes which accept two H atoms

Question 25

FAD

Answer 25

flavin adenine dinucleotide

Question 26

FMN

Answer 26

flavin mononucleotide

Question 27

Riboflavin deficiency

Answer 27

Common but rarely a problem: bacterial synthesis, conservation and re-utilisation

Question 28

Niacin

Answer 28

Vitamin B3 Precursor of co-enzymes NAD and NADP E- carriers in metabolic redox reactions

Question 29

Niacin synthesis

Answer 29

Synthesised from dietary tryptophan

Question 30

Niacin deficiency

Answer 30

Rare, Pellegra

Question 31

Vitamin B6

Answer 31

Pyridoxal phosphate Amino acid metabolism (transamination) Deficiency virtually unknown

Question 32

Vitamin B12 and Folate (B9)

Answer 32

Coenzymes - one carbon carriers DNA and myelin synthesis Deficiency - anaemia and neurological damage Folate supplementation in pregnancy

Question 33

Vitamin C

Answer 33

Ascorbic acid (a reducing sugar) and anti-oxidant Specific role in two enzyme classes -dopamine β-hydroxylase: synthesis or adrenaline and noradrenaline (Cu + dependent) -lysine and proline hydrolases: maturation of CT (collagen) Iron uptake: keeps iron as Fe2+, chelates it which > absorption

Question 34

Vitamin C deficiency

Answer 34

Scurvy -malaise, < wound healing, loose teeth Treated with limes, oranges, lemons

Question 35

Vitamins and dentistry

Answer 35

You may be first to spot deficiency Rapid turnover of epithelium makes it sensitive to nutritional deficiencies Vitamins involved with: wound healing, bleeding, resistance to infection, bone/ tooth Ca2+

Question 36

Oral manifestations of vit deficiencies in face

Answer 36

``` Malar pigmentation (Niacin, B vitamins) Nasolabial seborrhea (niacin, riboflavin, B6) Lack of colour (iron, malnutrition) ```

Question 37

Oral manifestations of vit deficiencies on lips

Answer 37

``` Cheilosis (niacin, B6, riboflavin) Angular fissures (niacin, B6, riboflavin, iron) ```

Question 38

Oral manifestations of vit deficiencies in gingiva

Answer 38

Spongy, bleeding, abnormal redness (vitamin C)

Question 39

Oral manifestations of vit deficiencies in tongue

Answer 39

Glossitis - red, raw, fissured (folate, niacin, iron, B6, B12) Pale, atrophic, smooth/ slick - filiform papillary atrophy (iron, folate) Magenta colour (riboflavin)