Module 1: Vitamins Flashcards
Why is choline not considered a vitamin?
It is made in the body but not in sufficient quantity so we must get it from food
It functions like a vitamin
But phosphatidylcholine in cell membranes of all food we eat - so we get enough
Fat soluble vitamins (include full names)
Vitamin A - retinol
Vitamin D - D2 ergocalciferol/D3 cholecalciferol
Vitamin E - alpha tocopherol
Vitamin K - napthoquinoids
Water soluble vitamins (include full names)
B1 - thiamine
B2 - riboflavin
B3 - niacin
B5 - pantothenic acid
B6 - pyridoxine
B7 - biotin
B9 - folic acid
B12 - cobalamin
Vitamin C - ascorbic acid
Choline - not a vitamin, but water soluble
Vitamin A roles
1) Essential for epithelial maintenance
symptoms: xerosis (keratin producing cells replace mucous secreting cells, cause abnormal dryness)
2) Vitamin A metabolites are ligands for RAR (retinoic acid) and RXR (retinoid x) nuclear receptor family
All trans RA ligands RAR in RXT heterodimer
9-cis trans RA ligands RXR in orphan dimer
Vitamin A deficiency symptoms
night blindness, eye xerosis causes ulcerations
associated with: poor lipid absorption
Vitamin A excess symptoms
birth effects due to teratogenic nature of retinoic acid
- > 10,000 IU per day in pregnant women is dangerous
reduced bone mineral density, weight loss, headaches, vision issues, dry itchy skin, hair loss, anemia, teeth discoloration, enlarged liver and spleen
Vitamin C role
Deficiency symptoms
1) co-substrate for prolyl and lysyl hydroxylases which add OH groups to Proline and Lysine residues
2) Acts an antioxidant
Deficiency leads to scurvy
Defective enzyme for vitamin C production in humans
Ascorbate transporters
defective L-gulonolactone oxidase
SCVT1 - transporter for ascorbate into enterocyte from apical side (lower affinity)
SCVT2 - transporter for ascorbate into enterocyte on basolateral side (high affinity)
GLUT transports dehydroascorbate into cells where it is converted to ascorbate, and then back to capillaries
Vitamin C and collagen formation
Vitamin C is a co-substrate for prolyl/lysyl hydroxylation
Without the addition of OH groups to proline and lysine, H bonds will not form properly to hold the pro-collagen triple coil and cross-linking of lysine residues in mature collagen fibrils
Choline roles
1) substrate for phosphatidylcholine production
2) As phosphatidylcholine ensures structural cell membrane integrity and and signaling functions
3) Acts as a source of methyl groups for methylation
4) Precursor to metabolites like: acetylcholine, platelet-activating factor and betaine (homocysteine metabolism)
De novo synthesis of choline is
3 successive methylations to phosphatidylethanolamine headgroup create phosphatidylcholine (which can be released)
Phytochemicals are
broad and diverse group of plant-derived compounds and plant-specific metabolites
Are NOT nutrients
Flavonoids are
subclass of phytochemicals with health benefits
