deck_4503545 Flashcards
What are the 4 fat-soluble vitamins?
A, D, E, K
What do fat-soluble vitamins require for abspt?
Bile and dietary fat
How are these vitamins transported?
W/ fats through lymphatic system in chylomicrons
Are these vits stored? Where?
Yes, in body fat (adipose tissue)>Thus intake can vary w/o risk of deficiency
e. Not easily excreted, unlike water soluble vitaminsi. **Increase … ii. Ppl should not take supplements high in these vitamins
FIGURE OUT
What are pre-made/preformed vit A called? Is it active or inactive? Toxic?
Retinoids: retinol, retinal, retinoic acidActive (usable)May be toxic
Where are retinoids found?
Animal foods>Liver, eggs, fortified into dairy, fish
What is the provitamin/precursor form of Vit A)? Is it active or inactive? Toxic?
CarotenoidsInactiveNon-toxic
Where are carotenoids found?
Plants → Yellow, orange, red fruits and veggies>More color, more carotenoids• Frozen and canned > retail fresh»Carrots, red bell peppers, cantaloupe
What is Retinoid fxn?
> Key role in night vision>Cell differentiation (key in fetal development)>Growth regulation”needed for vision (retinal), and for growth and differentiation of cells (retinoic acid)”
What is Retinoic Acid used for?
used topically to treat certain skin conditions (e.g. acne)>Vit A is a key component>Helps cells divide more rapidly, clearing old cells
What is fxn of Carotenoids? How absorbed?
Family of Phytonutrients>Decrease cancer risk and prevent macular de-generation»>In eye, (yellow) carotenoids have been shown to decrease risk of macular degeneration>Need dietary fat to be absorbed (absorbed in chylomicron)
(???) How are preformed and precursor forms of Vit A transformed in digestive tract?
> Preformed → Retinol transformed into Retinal >Precursor → Beta-carotene transformed into Retinal in liverand intestinal mucosa»_space;Retinal is converted to Retinoic Acid, can’t covert back
What is Vit A role in Visual Cycle?
> Vit A is a component of Rhodopsin (retinal + opsin) >When light hits, Retinal molecule changes molecular form»>Bent (cis) → straight (trans)»>Signals to brain that there’s light>Retinal breaks away from opsin → brain perceives light»>Retinal is lost in cycle»>Need more to form Rhodopsin»>If insufficient Retinal, eyes have difficulty adjusting to dark”- Retinal binds to opsin in the eye to form rhodopsin. After light strikes rhodopsin to begin the visual cycle, a nerve impulse is sent to the brain so the light is perceived.- When vit A is deficient, there is a delay in the regeneration of rhodpsin that causes difficulty seeing in dim light (night blindness).”
What is Vit A role in Gene Expression and Cell Differentiation ?
> Vit A has a role in directing which genes are transcribed and translated to create diff kinds of proteins»>Impt in early development and growth”- In order to affect gene expression, retinoic acid enters the nucleus of specific target cells, where it binds to retinoic acid receptor proteins; the retinoic acid-protein complex then binds to the regulatory region of DNA.”
What is relationship btwn Vit A and Keratin?
> Vit A helps w/ turnover of cells in eye that help w/ moisture and lubrication»>W/ insufficient Vit A, body creates Keratin, which leads to a hard and dry layer in the eye
Causes and symptoms of Vit A Deficiency?
Caused by insufficient intake of Vit A, fat>Night blindness>If severe: permanent blindness>Xerophathalmia – lack of mucous synthesis»>Keratin on the eye”More severe deficiency interferes w/ cell differentiation. This impairs immune fxn and growth and causes epithelial surface of eye to become hard and dry, leading to infection and blindness.”
Causes and symptoms fo Vit A Toxicity?
Retinoids – can be toxic and can increase risk of bone fractures and birth defects»_space;>Supplements (including multivitamin) have Vitamin A in multivitamins has been related to hip fractures in postmenopausal womenCarotenoids – not toxic, but high intake can cause»_space;>Hypercarotenemia: orange hue in skin, benign»_space;>Birth defects
What are dietary and other sources of Vit D? Essential?
Vit D = “sunshine vitamin” → Produced in the skin by exposure to UV light>Not found in many foods, mostly eggs, fatty fish (salmon), and milk (fortified dairy products)>Only conditionally essential in diet if you’re not producing enough through skin
What is active form of Vit D?
Vit D3, or Cholecalciferol>Modified in liver and then activated in kidney
Vit D toxicity?
Toxic at high lvls>Flynn – toxicity not thought to be issue, even w/ supplementation, but widespread use of vit D as supplement is relatively newBook info:»>High blood and urine Ca2+ concentrations»>Depositing of Ca2+ in blood vessels and kidneys, cardiovascular damage and possibly death
Vit D fxns?
> Bone health → maintains lvls of Ca2+ and P in blood that favor bone mineralization w/ calcium phosphate>Normal fxning of parathyroid gland>Regulation of immune system
How is Vit D synthesized? Where is it activated?
Light causes 7-dehydrocholesterol to be converted to Vit D3 → Needs to be activated in liver and then kidney
Is dietary Vit D3 active or inactive?
Inactive