Fat-Soluble Vitamins Lecture Notes

Vocabulary flashcards covering the biochemical forms, physiological functions, absorption pathways, deficiency diseases, and toxicities of fat-soluble vitamins A, D, E, and K.

Rhodopsin (Visual Purple)

A light-sensitive pigment formed by the combination of vitamin A and opsin in the rods of the eye, essential for vision in dim light.

Preformed Vitamin A

The active form of vitamin A found in animal foods that is readily utilized by the body, occurring as retinol, retinal, and retinoic acid.

Retinol

The storage and transport form of preformed vitamin A.

Retinal (Retinaldehyde)

An active form of vitamin A that participates directly in vision and serves as an intermediate in vitamin A metabolism.

Retinoic Acid

The form of vitamin A involved in gene regulation, cell differentiation, and cell growth.

Beta-Carotene ($\beta$-carotene)

The primary plant provitamin A carotenoid that is enzymatically converted into active vitamin A and also functions as an antioxidant.

Beta-Carotene Dioxygenase

An intestinal mucosal enzyme that cleaves one molecule of $\beta$-carotene into two molecules of retinal.

Micelles

Spherical structures formed by bile salts, fatty acids, monoglycerides, cholesterol, and fat-soluble vitamins that facilitate transport through the watery intestinal contents to mucosal cells for absorption.

Bitot's Spots

Foamy, soapy whitish patches that develop on the white part of the eye due to vitamin A deficiency, which do not impair eyesight and may persist after treatment.

Conjunctival Xerosis

An eye condition caused by vitamin A deficiency where the conjunctiva appears dry, rough, and wrinkled rather than wet, smooth, and shiny; curable in 1 to 2 weeks with supplementation.

Corneal Xerosis

A manifestation of vitamin A deficiency characterized by a dry and cloudy corneal surface, curable in early stages within 1 to 2 weeks of vitamin A therapy.

Hypervitaminosis A

Toxicity caused by excessive vitamin A intake—typically from supplements—occurring when binding proteins are overwhelmed and free vitamin A damages cells.

7-Dehydrocholesterol

A precursor sterol located in the skin that is converted to vitamin $D_3$ upon exposure to ultraviolet rays from sunlight.

Ergocalciferol (Vitamin $D_2$)

One of the two biologically significant forms of vitamin D, categorized chemically among sterols.

Cholecalciferol (Vitamin $D_3$)

A fat-soluble sterol vitamin synthesized in the skin from 7-dehydrocholesterol or obtained from dietary sources, structurally similar to cholesterol.

Rickets

A pediatric bone disorder resulting from vitamin D deficiency, characterized by poor bone mineralization, soft bones, bowed legs, knock-knees, and delayed or abnormal dentition.

Osteomalacia

An adult condition caused by vitamin D deficiency where defective bone building causes bones to become soft and rubbery; common in multiparous and postmenopausal women.

Hypervitaminosis D

A toxic state resulting from excess vitamin D that leads to elevated blood calcium, liver stress, kidney stones, and soft tissue or vascular calcification.

Tocopherol (Vitamin E)

A fat-soluble vitamin occurring in alpha-, beta-, gamma-, and delta- forms that functions as a potent antioxidant protecting cell membranes and polyunsaturated fatty acids from oxidation.

Free Radicals

Highly reactive molecules capable of damaging cellular components, which are neutralized by antioxidants such as vitamin E and $\beta$-carotene.

Phylloquinone (Vitamin $K_1$)

The dietary form of vitamin K derived from plant sources such as fresh green leafy vegetables.

Menaquinone (Vitamin $K_2$)

The form of vitamin K synthesized by bacterial flora within the large intestine.

Prothrombin

A blood-clotting protein whose synthesis depends on vitamin K for normal coagulation.