Human Biochemistry, Volume 2 - Murray R. 1993
Special Topics
Nutrition, Digestion, and Absorption
Mineral Requirements
Minerals essential for physiological Functions can be broadly divided into two groups: 1) macrominerals, which are required in amounts exceeding 100 mg per day, and 2) Trace Elements (microminerals), whose daily requirement does not exceed 100 mg. The relevant data are presented in Table 53.1. Table 53.8 summarizes The properties of macrominerals, and Table 53.9 outlines the properties of trace elements.
Class="center">Table 53.6. Major Fat-soluble Vitamins. Principal properties
|
Vitamin / Provitamin 1) |
Active metabolite: physiological function |
Deficiency disease or symptoms |
Toxicity disease or symptoms |
Sources |
|
|
Vitamin A Provitamin: ß-carotene Vitamin: retinol |
Transported into the Lymph as retinyl esters; bound in the Blood to retinol-binding protein and prealbumin |
11-cis-Retinal — component of rhodopsin and other light-absorbing pigments. Unidentified metabolites (retinoic acid?) are required for the growth and differentiation of epithelial, neural, and Bone Tissues |
Children: impaired dark adaptation, Skin dryness, keratomalacia, growth retardation, death Adults: night blindness, xeroderma |
Hypervitaminosis A: headache, dizziness, nausea, skin desquamation, bone pain |
Brightly colored vegetables (containing carotenes), hard margarine |
|
Vitamin D Provitamins: ergosterol (plants, Yeast) and 7-dehydrocholesterol (skin) |
Provitamins are converted into vitamins upon ultraviolet irradiation. The vitamins are hydroxylated in the Liver to form 25-hydroxyvitamin D and in the Kidneys to form 1,25-dihydroxyvitamin D and other metabolites |
1,25-dihydroxyvitamin D — the primary hormonal regulator of Mineral Metabolism (Calcium and phosphorus) in bones |
Children: Rickets Adults: Osteomalacia |
Hypervitaminosis D: hypercalcemia, hypercalciuria, nephrocalcinosis |
Fortified milk, sun exposure of the skin |
|
Vitamins D2 (ergocalciferol) and D3 (cholecalciferol) |
|||||
|
Vitamin E Tocopherols, tocotrienols |
Incompletely understood |
Active metabolite unknown. Functions as an antioxidant |
Children: anemia in premature infants Adults: no known syndromes |
Not established. High doses impair Vision (blurred vision) and cause headaches |
The primary source is vegetable oils |
|
Vitamin K: K1 (phylloquinone), K2 (menaquinone), others |
Incompletely understood |
Active metabolite unknown, but likely a hydroquinone derivative. Activates blood clotting factors II, VII, IX, and X via y-carboxylation of glutamic acid residues; also carboxylates bone and Kidney Proteins |
Children: hemorrhagic disease of the newborn Adults: impaired Blood Coagulation. Deficiency symptoms may be induced by coumarin anticoagulants and antibiotic therapy |
May be caused by Water-dispersed analogues: hemolytic anemia, liver damage |
Synthesized by intestinal Bacteria |
1) Fat-soluble vitamins are insoluble in water but soluble in fats and oils. They are relatively stable at ordinary cooking temperatures, but are inactivated by ultraviolet light and oxidation.
2) Dietary fat and Bile are required for the absorption of fat-soluble vitamins; malabsorption or biliary obstruction leads to vitamin deficiency. Lipoproteins or specific carrier proteins are involved in vitamin transport. Fat-soluble vitamins are stored primarily in The Liver and, to some extent, in adipose tissue. Vitamins are excreted into the bile and either reabsorbed via enterohepatic Circulation or excreted in the feces. Some metabolites may be excreted in the urine.
3) Dietary sources for all fat-soluble vitamins include green leafy vegetables, vegetable oils, fatty meats, and dairy products, In addition to the specific sources listed in the table.
Table 53.7. Vitamin-responsive syndromes. Examples of specific Metabolic Disorders of vitamin Cofactors that respond to high-dose vitamin therapy. (From: Herman R. Н., Stifel F. В., Green H. L. Vitamin-deficient states and other related diseases. In: Disorders of the Gastrointestinal Tract; Disorders of the Liver; Nutritional Disorders. Dietschy J. M. (editor). Grune and Stratton, 1976.)
|
Vitamin |
Disease |
Biochemical defect |
|
Biotin |
Propionic acidemia |
Propionyl-CoA carboxylase |
|
Vitamin B12 |
Methylmalonic aciduria |
Cobamide coenzyme formation |
|
Folate malabsorption |
Folic acid transport |
|
|
Niacin |
Hartnup disease |
Tryptophan transport |
|
Pyridoxine (vitamin B6) |
Neonatal seizures Cystathioninuria Homocystinuria |
Glutamate decarboxylase (?) Cystathionase Cystathionine synthase |
|
Thiamine |
Hyperalaninemia Thiamine-responsive lactic acidosis |
Pyruvate decarboxylase Hepatic pyruvate carboxylase |
Last update: 06/08/2026
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