Exam 3 - Chpt 9-11 Flashcards
(91 cards)
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
How do fat soluble vitamins compare to water soluble?
Not easily excreted, unlike water soluble vitamins
>Ppl should not take supplements high in these vitamins
What are pre-made/preformed vit A called? Is it active or inactive? Toxic?
Retinoids: retinol, retinal, retinoic acid
Active (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?
Carotenoids
Inactive
Non-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 and growth
“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?
Decrease cancer risk and prevent macular de-generation
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 liver and intestinal mucosa
> > 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 strikes rhodopsin, a nerve impulse is sent to brain so light is perceived.
When Vit A is deficient, there is delay in regeneration of rhodpsin that causes difficulty seeing in dim light (night blindness)
—
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
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
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
Symptoms of Vit A Deficiency?
> Night blindness
If severe: permanent blindness
Xerophathalmia – lack of mucous synthesis
»Keratin on the eye
Causes and symptoms of Vit A Toxicity (each form)?
Retinoids – can increase risk of bone fractures and birth defects
>Vit A supplements linked to hip fractures
Carotenoids – not toxic, but high intake can cause
>Hypercarotenemia: orange hue in skin, benign
>Birth defects
What are dietary and other sources of Vit D? Essential?
Vit D = “sunshine vitamin” → Produced in skin by exposure to UV light
>Found in 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?
May be toxic at high lvls
>Flynn – toxicity not thought to be issue, even w/ supplementation
Book info:
>High blood and urine Ca2+ concentrations
>Depositing of Ca2+ in blood vessels and kidneys, cardiovascular damage, 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 converts 7-dehydrocholesterol to Vit D3 → activated in liver, then kidney
Is dietary Vit D3 active or inactive?
Inactive