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Questions and Answers
What happens to the rhodopsin molecule when light falls on the eye?
What is the result of a severe vitamin A deficiency in the eye?
What is the role of retinoic acid in the body?
What happens to epithelial tissue when vitamin A is deficient?
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What is the consequence of vitamin A deficiency in the lungs?
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What is the role of vitamin A in men?
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What is the function of retinoic acid in the body?
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Where is retinol, an active form of vitamin A, primarily stored in the body?
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What is the function of beta-carotene in the body?
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What is the difference between vitamin A from animal-derived foods and plant-derived foods?
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What is the role of vitamin A in the maintenance of body linings and skin?
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Study Notes
Vitamin A
- Vitamin A was the first fat-soluble vitamin to be recognized
- Vitamin A and its precursor, beta-carotene, are still an area of research
Forms of Vitamin A
- There are 3 active forms of vitamin A: Retinol, Retinal, and Retinoic acid
- Retinol is an antioxidant nutrient stored in the liver
- Retinal is converted by the cells to retinol as needed
Roles of Vitamin A
- Gene expression
- Vision
- Maintenance of body linings and skin
- Immune defenses
- Growth of bones and of the body
- Normal development of cells
- Reproduction
Vitamin A in Eyesight
- Vitamin A plays 2 roles in eyesight: in the process of light perception at the retina and in the maintenance of a healthy cornea
- Rhodopsin, a pigment in the retina, contains vitamin A, which breaks off when light falls on the eye and reunites with the pigment after bleaching
- A lack of vitamin A can cause night blindness
Night Blindness
- Night blindness occurs when the vitamin A supply is low, causing a lag before the eye can see again after a flash of bright light at night
Xerophthalmia and Blindness
- A more profound deficiency of vitamin A causes keratinization of the cornea, leading to xerophthalmia (drying) and permanent blindness
- Half a million vitamin A-deprived children become blind each year due to xerophthalmia
Gene Regulation
- Retinoic acid, a form of vitamin A, regulates hundreds of genes that direct the synthesis of proteins that perform metabolic work in tissues
- Vitamin A affects the metabolic activities of tissues and, in turn, the health of the body
Cell Differentiation
- Vitamin A is needed for cell differentiation in epithelial tissue, such as the protective linings of the lungs, intestines, vagina, urinary tract, and bladder
- Cell differentiation is essential for the development of specific cell functions, such as mucus production in goblet cells
- Vitamin A deficiency leads to the failure of cells to make mucus, allowing keratin to accumulate and making tissues vulnerable to infection
Immune Function
- Vitamin A has an "anti-infective" reputation and is essential for immune defenses
- A lack of vitamin A weakens the body's defenses, making illness more severe
Reproduction and Growth
- In men, vitamin A is necessary for the formation of sperm
- Vitamin A is essential for reproduction and growth
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Description
Learn about Vitamin A, the first fat-soluble vitamin to be recognized, and its plant-derived precursor, beta-carotene, which has antioxidant activity. Explore their functions and food sources.
