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Nutrition > Vitamins > Flashcards

Vitamins Flashcards

1
Q

Vitamins - why do we need them

A 
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)
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2
Q

Vitamins structure

A 
Chemically disparate
Organic compounds (trace elements and minerals: inorganic)
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3
Q

Vitamins functions

A 
Co-enzymes
Hormones
Cell signalling
Antioxidants
Regulators of growth and differentiation
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4
Q

How were vitamins found

A 
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)
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5
Q

Biological availability and adsorption

A

< 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

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6
Q

Recommended daily allowance

A

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.

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7
Q

Fat soluble vitamins

A

A, D, E, K

In general fat soluble can be stored, water soluble not

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8
Q

Water soluble vitamins

A

B vitamins, C

In general fat soluble can be stored, water soluble not

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9
Q

Vitamin A

A 
Retinoids (active form)
Carotenoid pigments (e.g. β carotene) in plants cleaved to yield retinoids
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10
Q

Vitamin A functions

A

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

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11
Q

Vitamin A deficiency

A

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)

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12
Q

Vitamin D

A 
Hormone precursor
-vitamin D3 calciol/ cholecalciferol
-vitamin D2 ercalciol/ ergocalciferol
Endogenous synthesis more important than dietary sources 
-D3 - photolysis of 7-dehydrocholesterol
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13
Q

Vitamin D functions

A

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

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14
Q

Bone metabolism

A

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

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15
Q

Vitamin D deficiency

A

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)

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16
Q

Vitamin E and function

A

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

17
Q

Vitamin K and function

A

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

18
Q

Vitamin K: klotting

A

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

19
Q

B vitamins examples

A 
Thiamin (B1)
Ribofavin (B2)
Niacin (B3)
B6
Folic acid (B9)
B12
Panthothenic acid (B5)
20
Q

B vitamins functions

A

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

21
Q

Thiamin

A

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

22
Q

Thiamin pentose phosphate pathway

A

Co-enzyme

Transketolase: NADPH for biosynthesis and ribose for nucleotides

23
Q

Thiamin deficiency

A

Berberi-peripheral neuritis: weakness, stiffness

24
Q

Riboflavin

A

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

25
Q

FAD

A

flavin adenine dinucleotide

26
Q

FMN

A

flavin mononucleotide

27
Q

Riboflavin deficiency

A

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

28
Q

Niacin

A

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

29
Q

Niacin synthesis

A

Synthesised from dietary tryptophan

30
Q

Niacin deficiency

A

Rare, Pellegra

31
Q

Vitamin B6

A

Pyridoxal phosphate
Amino acid metabolism (transamination)
Deficiency virtually unknown

32
Q

Vitamin B12 and Folate (B9)

A

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

33
Q

Vitamin C

A

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

34
Q

Vitamin C deficiency

A

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

35
Q

Vitamins and dentistry

A

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+

36
Q

Oral manifestations of vit deficiencies in face

A 
Malar pigmentation (Niacin, B vitamins)
Nasolabial seborrhea (niacin, riboflavin, B6)
Lack of colour (iron, malnutrition)
37
Q

Oral manifestations of vit deficiencies on lips

A 
Cheilosis (niacin, B6, riboflavin)
Angular fissures (niacin, B6, riboflavin, iron)
38
Q

Oral manifestations of vit deficiencies in gingiva

A

Spongy, bleeding, abnormal redness (vitamin C)

39
Q

Oral manifestations of vit deficiencies in tongue

A

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

Nutrition (13 decks)

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