Vitamin A And Carotenoids Flashcards
What must happen for retinol to be incorporated into chylomicrons for transport
Retinol esterified
Retinol is esterified by
Cellular retinol-binding protein (CRBP) II
What carries vit A and carotenoids to liver?
What happens there?
–Chylomicrons carry to liver
–Additional metabolism in liver
What is primary transport for retinol in the blood from the liver
Retinol binding protein complex with transthyretin
What type of retinol can be stored in the liver
Esterified
Where is esterified retinol stored in liver
•Stellate cells* & parenchymal cells
2 proteins that transport vit A in the blood
- Retinol-binding protein (RBP)/Transthyretin (TTR)
* Albumin
What form of vit A does albumin transport
Retinoic acid
Carotenoids can be transported to other tissues by chilomicrons
T/F
T
What transports carotenoids from liver
Lipoproteins
Carotenoids transported as part of lipoproteins and percentages
- 50% α-, b-carotene and lycopene in LDL
- 25% in HDL
- 16% VLDL
Carotenoids stored in
liver & adipose
Retinoic acid is made in small amounts by
individual cells from retinal and works within individual cells
What form of vit A is important for vision
11 cis-retinal (Rhodopsin)
–All-trans retinoic acid and 9-cis retinoic acid is important for what 4 things
- Gene expression
- Cellular differentiation
- Growth and Reproduction
- Bone metabolism – Osteoblasts/clasts
What types of cells do All-trans retinoic acid and 9-cis retinoic acid affect for cellular differentiation
Keratinocytes
Growth and reproduction is assisted by what form of vit A
Retanoic acid
In what 4 ways is retinoic acid important for cellular differentiation and growth
- Helps maintain normal structure and function of epithelial cells
- Directs differentiation of keratinocytes (immature skin cells) into epidermal cells through changes in gene expression
- Increases the synthesis of gap junction proteins (essential for cell to cell communication)
- Stimulate glycoprotein synthesis which can stimulate differentiation
Excess Vit A interferes with absorption of?
Vit K absorption
High b-carotene intake may decrease plasma
Vit E
What 2 things influence Vit A status and transport
–Protein & zinc
Iron metabolism interrelated with both
carotenoids and Vitamin A
In what two ways is iron related to Vit A and carotenoids
- Required for conversion of b-carotene to Vit A
* Vitamin A deficiency may be associated with iron-deficiency anemia
- 1 RAE = 1 μg retinol = 12 μg β-carotene = 24 μg α-carotene or β-cryptoxanthin
- In other words, 12 times the amount of β-carotene or 24 times the amount of α-carotene or β-cryptoxanthin is needed to get the same effects as 1 μg of retinol
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