Vitamin A (Retinol) Biochemistry

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Vitamin A is a group of fat-soluble compounds that includes retinol, retinal, retinoic acid, and several provitamin A carotenoids (notably beta-carotene) found in leafy greens. Vitamin A is an antioxidant, and it has a number of functions.  These functions include growth and development, cell differentiation and immune maintenance, the formation of visual pigments, and the treatment of acne (isotretinoin) and measles. ATRA (all-trans retinoic acid), a form of vitamin A, is used to treat the APL, also known as acute promyelocytic leukemia (subtype of AML).

Key Points

  • Retinol (Vitamin A)
    • Antioxidant found in:
      • Wild game/animal products, especially liver (preformed vitamin A)
      • Leafy vegetables (as beta-carotene precursor)
    • Fat-soluble
      • Fat malabsorption in biliary/pancreatic insufficiency (e.g. cystic fibrosis) can cause Vitamin A Deficiency
    • Constituent of retinal visual pigments
      • Deficiency or excess can affect vision
    • Maintains normal cell differentiation
      • epithelial cells into specialized tissue (pancreatic cells, mucus-secreting cells)
        • prevents squamous metaplasia
      • Promyelocytes into mature granulocytes
        • Mechanism of action for treating APL (subtype of AML)
    • Inhibits sebum production in sebaceous glands
      • used to treat cystic acne
    • Also used to treat measles

Find Vitamin A Biochemistry and other Vitamins among Pixorize's visual mnemonics for the USMLE Step 1 and NBME shelf exams.