Lecture 21 Flashcards
What does the term Vit A describe?
Describes retinol and related structures and the pro Vitamin A carotenoids
What do retinoids include?
- Retinol
- Retinal
- Retinoic acid
What are carotenoids?
- Plant pigments
- Combination of retinoid structures
What is the role of carotenoids?
- Makes plants pigmented yellow, orange, red
- Helps light absorption for photosynthesis
- Acts as antioxidant
What are the functions of Vit A?
- Eye by maintaining healthy corneas, epithelial cells, mucous membranes, and vision
- Reproduction
- Growth
- Health of epithelial tissues and kin by protein synthesis and cell differentiation
- Immunity
Describe the 2 roles of Vit A in vision
- Key component of the visual cycle
- 11-cis retinal is component of chromophore found in two types of receptor cells. When light hits it is converted from cis->trans - Rod cells
- chromophore protein part is rhodopsin
- 100 Million
- low light intensity - Cone Cells
- chromophore protein part is iodopsin
- 3 million
- Higher light + colour - Health of epithelial cells
- Retinoic acid
- Need to keep eye moist
What’s the first sign of a Vit A deficiency?
Dry eyes
What is night blindness?
- The inability to see in dim light
- Very common and reversible
What % of children and at what age does night blindness affect?
- Affects 1% of children
- Ages 6months - 6 years
What is Vit A’s role in epithelial cells?
Cell differentiation with retinoc acid
What is Vit A’s role in reproduction?
- Sperm development
- Normal fetal development
How is the NZ diet for Vit A?
Slightly below RDI
What food sources give retinoids?
- Liver is the richest source
- Milk, butter, cheese, egg yolk, some fatty fish (dairy)
What food sources give carotenoids?
-Dark green leafy vege, yellow/orange coloured fruit/vege
How is Vit A absorbed?
Integrated into chylomicrons via micelles, then into the lymph
