Vitamin A Flashcards
(35 cards)
بسم الله الرحمن الرحيم وبه نستعين
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MentioN Characteristics of Fat soluble vitamins
Absorbed with dietary fat
Transported in blood in Lipoproteins + sepcific binding proteins
Not readily excreted as significant amount are stored in liver and adipose tissue so excess in take can cause toxicity
KEDA
Anti xeroptlamic
anti night blindeness vitramins is ?
Vitamin A
Show structure of vitamin A
Polyisoprenoid compound
Hydrocarbon + B-Ionone ring
Preformed Vitamin A is ?
Retinyl Ester in animal foods also stored in liver
Retinyl ester =Retinol + fattay acid
Mention active forms of Vitamin A
Retinol
Reitinal
Retinoic Acid
The reversible reaction in vit A active form transormation
Retinol to Retinal is Reversed by reduction reaction
Preformed vit A is ?
ProVit A is ?
Preformed =Reinyl ester from animal
ProVit = B carotence percursor of vitamin A by Carotenase
Mention soruces of Vitamin A
الجزر غني عني التعريف ^_^
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=Animal sources Retinyl ester preformed vit A :- Liver- cod liver oil - kideny- butter -cream -egg yolk
=Plant sources Provit A or B carotene :- ? Carrots - dark green leafy vegetables + fruits
peaches + apricot + sweet potato
why conveseion of B carotene into Retinal is non efficent ?
Due to low activity of the enzyme carotenase or carotene dioxygenase and the retionl formed from it represnts only 1/12 of the yield retionl
The only Vit A form that is not carried by RBP but carried by….. ?
It is Retinoic acid
carried by albuimen
Explain Absoprtion and transport of Vitamina A
When RE reaches the Intestine the ester disscoiates leaving the Retionl which is incroprated with B carotene in the miscelle ( Phosplipids- Cholesterol- Fattay acids - MOno acyl glycerol )
The miscelle enters the intestinal eipthelial cells where:-
B carotene converted into 2 retinal by Carotenase or carotene dioxygenase and some escapes the enzyme then retinal reduced into retionl
The retinol released already from miscelle + Retionl from B carotene are Esterified into REs which are incorporated into Chylomicrons with the ecaping B carotene
then CM enters lymph then blood converted into CM remenatns then to liver where retinyl ester becomes retionl to reach its target cell or the retiol will be stored as Reinyl palmitate
B carotene is carried By VLDL to be stored in Adipose tissue
What is the fate of B carotene in intestine ?
Absorbed in miscleele into the intestinal cell then:
1-Carotenase works on it to form 2 retinal then reduced to 2 retionl
2- Escapes carotenase to be in CM directly
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after reaching liver carried in VLDL to be sotred in adipose tissue
stored from of vit A in liver?
Retinyl palmitate
Daily requirements of Vit A is > ?
RDA for adults 900 retional activity equivalent RAEs for male
700 RAEs for females
1 RAEs= 1 ug Retionl = 12 ug B carotene
Mentione Role vitamin A in vision ?
It is compnent of visual pigment of photorecpeotr cells of reds and cones which absop light causing chemical changes and nerve impulse discharge!
Mention function ofMet Rhosopsin
Metrhodopsin fromed G protein stimulation causing hyperpolarization of receptors casuing finally depolarization of nerves ( optic nerve) to brain
Explain Viscual cycle of dim light
or Explain Rhodopsin cycle
11 Cis retinal + Oposin ( Rhodopsin )
when light Fall on this complex
Oposin disocciate from 11 cisretinal
and Metrhodopsin fromed G protein stimulation causing depolarization of nerves to brain
11 cis retinal disscoiates as All Trans RetinAl
then redcued to All trans RetinOl THEN transported to ? Retinal pigment epithelium where its is esterfied into All trans RE then isomer formed ( 11 cis RetinOl )
then Oxidized to 11 cis retinal (required ) enter the Rod cell to attach to opsin formin Rhodsopsin complex and the cycle completed
mention function of 11 cis retinal
attach to Opsin in rods forming rhosopisn for dim light
attach to opsin if cones forming iodopsin for brigh light and colors
Mention role in vit A in immunce cells
mention role of Vit A in cell differentiation and turnover
Retinoic acid attaches to Nuclear protein receptor then to Element of DNA stimlating transcrioptin of gene to mRNA - protein in cell differentiation and turnover
Vit A plays a role in maintanece of healthy epithleum show
Retinyl phospate from retionl works as glycosyl carries for synthesis of glycoproteins + Mucopolysaccharides for muscin secretion
Mention role of vit A in reproduction
Retinol and Retinal plays an imprtant role in sepermatogensis and preventing fetal resprobtipin in felmale rats
What happens if animal is only given reinoic acid as a source of Vit A
Plays its role in cell differentiation but
no role in reproduction so ?
Sterile Animal and blind
What happens if animal is only given reinoic acid as a source of Vit A
Plays its role in cell differentiation but
no role in reproduction and visual cycle so ?
Sterile Animal and blind
B carotene and health ?
It is antioxidant trap free radicals at low oxygen pressure
May protect against? Cancer + heart attack
