MIdterm 2 Section 5 Flashcards
teratogenic definition
toxic side effects
vitamin A deficiencies and toxicity side effects
deficiency can lead to blindness, susceptibility to measles
toxicity can cause birth defects
retinal deficiency: night blindness
retinoic acid deficiency: bitot’s spots, xerophthalmia, keratomalacia
vitamin A forms and functions
food sources: retinoids (animal) and carotenoids (plant)
converted in the body: retinol (from retinoids) –> retinal –> retinoic acid
supplement sources: retinyl ester
retinol - supports reproduction
retinal - participates in vision
retinoic acid - regulates growth
what role does vitamin A play in sight?
within the retinal cells (rods and cones) in the back of the eye
retinal sits in a cis configuration as part of rhodopsin, adjacent to the opsin protein
when a photon hits rhodopsin (low intensity light), retinal changes to trans configuration, sending an electrical impulse to the brain
bitot’s spots
lesions that appear in the white of the eye due to retinoic acid deficiency
xerophthalmia
dry eyes
keratomalacia
Changes structure of surface of eye, causes drying and clouding
Causes irreversible blindness
Due to retinoic acid deficiency
Cataracts
Lens becomes less flexible with age (difficulty seeing up close)
Cataracts - lens gets cloudy, surgery vibrate lens to break up lens and take it out, and then replace the lens
Vitamin A role in mucous membrane health
Necessary in mucous membrane of GI and lungs
Maintains differentiated goblet cells and columnar cells
Allows pathogens into the body more easily
GI and respiratory illness risk increases
Retinoic acid functions
1) cell differentiation: controls gene expression
- goblet/epithelial cells and embryonic growth (deficiency/toxicity)
- membrane integrity, taste, digestion, absorption, malformations in toxicity
2) Immunity: direct and indirect (epithelium)
3) Growth: cell division and bone remodeling
RDA and UL for vitamin A
in RE retinol equivalents
500mg RE RDA
15000mg RE UL
Good food sources of vitamin A or beta carotene
dark green and deep orange veggies
sweet potatoes, beef liver, dairy is fortified, carrots, broccoli
vitamin K forms and function
phylloquinone - plant form
menadione - vitamin form
functions:
- carboxylation of glutamic acid residues in proteins to enable Ca binding (ex. osteocalcin)
- blood clotting cascade
vitamin K deficiency occurs with
fat malabsorption, newborns, antibiotic use
contraindicated with anti-clotting drugs
vitamin K in the blood clotting cascade
vitamin K helps to form a prothrombin precursor
calcium and thromboplastin activate prothrombin to thrombin active enzyme
fibrinogen and thrombin form a mesh to trap RBC and clot