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Questions and Answers
What is the primary source of vitamin D for humans?
What is the function of 25-hydroxycholecalciferol in the liver?
What is the main function of vitamin D in the body?
What is the active form of vitamin D produced in the kidney?
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What is the result of vitamin D deficiency in adults?
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What is the primary function of vitamin E?
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What is the most active form of vitamin E?
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What is the consequence of taking excessive vitamin D supplements?
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What is biochemistry primarily concerned with?
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Which nutrient category do vitamins fall under?
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How do vitamins typically function in biochemical processes?
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What must be supplied by the diet since the body generally cannot synthesize them?
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Which of the following roles do vitamins NOT play in the body?
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What is the significance of vitamins in relation to enzymes?
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What is the primary difference between water-soluble and fat-soluble vitamins?
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Which of the following is NOT a function of vitamin A?
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What is the difference between retinoids and carotenoids?
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Which of the following is a potential consequence of chronic vitamin A toxicity?
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What is the recommended upper limit of vitamin A intake for women who are pregnant or may become pregnant?
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Which of the following is a common sign of vitamin A deficiency?
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What is the most important role of retinoic acid in the body?
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What is the main difference between the treatment for water-soluble and fat-soluble vitamin deficiencies?
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Study Notes
Biochemistry
- Biochemistry is the science concerned with the study of chemical reactions that occur in living organisms.
Vitamins
- Vitamins are organic nutrients required in small quantities for various biochemical functions and cannot be synthesized in the body.
- Vitamins assist in the formation of hormones, blood vessels, nervous system chemicals, and genetic materials.
- Vitamins act as catalysts, combining with proteins to create metabolically active enzymes essential for life reactions.
Classification of Vitamins
- Vitamins can be classified into water-soluble and fat-soluble vitamins.
Water-Soluble vs Fat-Soluble Vitamins
- Water-soluble vitamins:
- Are soluble in water
- Are absorbed simply
- Are not stored in the body
- Are excreted
- Excess intake is non-toxic
- Deficiency manifests rapidly
- Treatment involves regular dietary supply
- Fat-soluble vitamins:
- Are soluble in fat
- Are absorbed along with lipids
- Are stored in the liver
- Are not excreted
- Excess intake is toxic
- Deficiency manifests slowly
- Treatment involves a single large dose
Fat-Soluble Vitamins: Vitamin A
- Vitamin A occurs in two forms in food: retinoids and carotenoids.
- Retinoids are preformed vitamin A found only in foods of animal origin.
- Carotenoids are found in plants, comprise carotenes and related compounds, and are known as provitamin A.
- Vitamin A functions include:
- Vision
- Antioxidant activity
- Regulation of gene expression and tissue differentiation
- Essential for health and growth
- Essential for bone formation and calcification
- Gene regulation during early fetal development
- Vitamin A toxicity can occur with doses above 200 mg of retinol or retinal, or chronic consumption of more than 40 mg/day, causing symptoms such as gastrointestinal issues, neurological symptoms, dermatological symptoms, and musculoskeletal issues.
- Vitamin A deficiency can cause night blindness, xerophthalmia, infections, keratinization of skin, and impairment of immune responses.
Fat-Soluble Vitamins: Vitamin D
- Vitamin D is not strictly a vitamin since it can be synthesized in the skin, and under most conditions, that is its major source.
- Vitamin D is present in two forms: ergocalciferol (vitamin D2) found in plants and cholecalciferol (vitamin D3) found in animal tissues.
- Vitamin D is present in only a few natural foodstuffs, including liver, egg yolk, and saltwater fish.
- The main function of vitamin D is in the regulation of calcium absorption.
- Vitamin D is synthesized in the skin by the action of ultraviolet radiation, and then hydroxylated to 25-hydroxycholecalciferol in the liver and further hydroxylated to 1,25-dihydroxycholecalciferol (calcitriol) in the kidney.
- Vitamin D deficiency can cause rickets in children, osteomalacia in adults, and osteoporosis.
- Vitamin D toxicity, caused by overuse of supplements, leads to hypercalciuria and metastatic calcification (abnormal calcification of soft tissues).
- Symptoms of vitamin D toxicity include anorexia, weight loss, irregular heart beat, and hardening of blood vessels and tissues due to increased blood levels of calcium.
Fat-Soluble Vitamins: Vitamin E
- Vitamin E is the generic descriptor for two families of compounds: the tocopherols and the tocotrienols.
- The most active form is D-α-tocopherol.
- The main function of vitamin E is as a chain-breaking, free radical-trapping antioxidant in cell membranes and plasma lipoproteins.
- Vitamin E is an antioxidant and scavenger of free radicals, protecting membranes, fat depots, and lipoprotein from lipid peroxidation.
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Description
Test your knowledge of biochemistry, vitamins, and minerals. This quiz covers various aspects of biochemistry, including vitamins and minerals like Na, Mg, Fe, and Ca.
