Vitamins Flashcards
Name fat soluble vitamins
vitamin A, vitamin D, vitamin E, vitamin K
Name water soluble vitamins:
B complex vitamins (9×), vitamin C
What are provitamins?
Provitamins are precursors to vitamins themselves.
What are vitamers?
Vitamers are different forms of a vitamin (‘vitamin isomers’).
All vitamers are isoprenoids. ‘All-trans’ versions are usual in diet and only change to cis when in use.
Vitamin A (retinol) talk about those below?
Retinaldehyde
Retinyl palmitate and carotenes
Retinol
Retinoic acid
*The vitamer of vitamin A are retinoic acid, retinaldehyde (retinal), retinol, retinyl esters
* Provitamins are; β-carotene, α-carotene, γ-carotene etc,
* Retinaldehyde (retinal) is used in the eye to form rhodopsin, needed in low-light vision.
* Retinyl palmitate and carotenes are main forms in our diet, converted to retinol in small intestine.
Retinol is the storage form.
* Retinoic acid is synthesised from retinol in male gonads (needed for sperm generation) and in embryos (regulates brain development).
Used as pharmaceutical (Tretinoin) for reversing photoaging of skin, treatment of acne and some cancers.
- Supplement is usually β-carotene as retinol etc are toxic if too much is taken orally. Hypervitaminosis A can kill
Hypovitaminosis A
What are these?
xerophthalmia
keratomalacia
nyctalopia
- xerophthalmia – thickening of surface layers of the
eye. - keratomalacia – similar with inability to synthesise
specialist tissues of eye surface – opaque cornea
develops. - nyctalopia (night blindness) – lack of retinaldehyde (and thus rhodopsin) in retina.
- photophobia – aversion to bright light owing to lack of light-absorbing rhodopsin in retina.
- causes weight loss and blindness
prevent with Cod liver oil, sweet potato and carrots
Fat soluble: Vitamins D
- Cholecalciferol (D3) is Produced in the skin of Mammalia by
photodependent pathway (λ = 290-315 nm).
ergocalciferol (D2) is produced in Fungi in same way. - Regulates intestinal calcium uptake.
Hypovitaminosis D
Hypovitaminosis D found in people with skin with high
melanin content, in people with very low body fat
and in people whose skin seldom sees direct sunlight
without SPF.
* rickets – bone softening in children. Called osteomalacia in adults.
* osteoporosis – bones become porous and fragule.
* clinical depression and clinical anxiety – common
symptoms of early stages of hypovitaminsis D.
* schizophrenia – not necessarily a symptom but many patients therewith have low serum vitamin D
levels.
* muscular pain
* muscle twitching
prevent with cod liver oil, mushrooms and canned tuna
Fat soluble: Vitamin E
What are the vitamers?
- Potent antioxidants (aka reducing agents Important in handling oxidativemstress).
Protects cell membranes.
Eight vitamers – 4 are tocopherols, 4 are tocotrienols. Names are prefixed with α, β, γ, δ. Supplements usually use α tocopheryl
acetate as it’s more stable in long-term storage.
Hypovitaminosis E
*causes neurological damage but very rare – only occurs if dietary lipid uptake is not functioning.
prevent with wheat germ oil, oily fish and rapeseed oil
Fat soluble: Vitamin K
* Two vitamers phylloquinone (K1) and
menaquinone (K2)
menaquinones (MKs) are respiratory chain quinones in many Bacteria and Archaea
– we obtain them from our gut microflora, like Escherichia coli, which leaks them into the gut.
K1is found in photosynthetic electron transfer chain in the Viridiplantae and green leaves are best dietary source.
- Hypovitaminosis K
*causes issues with blood clotting and with proper Ca metabolism.
prevent with green leafy vegetables,
Water soluble: Vitamin C
- Potent antioxidant (reducing agent) – key in handling oxidative stress within the cytoplasm or in extracellular fluids.
Enzyme cofactor e.g. hydroxylases involved
in collagen biosynthesis.
Hypovitaminosis C
- overarching condition is scurvy
- bleeding gums
- rashes
- fatigue
- easy bruising
- wounds not healing
- neuropathy
- personality changes
prevent with rosehip, blackcurrents and citrus fruit
Water soluble: thiamine (B1)
- Enzyme cofactors are made from it – critical glycolytic pathways
- Essential for many Bacteria.
