Vitamins in Medical Biochemistry

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Questions and Answers

What is the result of xerophthalmia persisting for a long time?

Keratomalacia (correct)

Corneal opacities

Vitamin D deficiency

Degeneration of conjunctiva

What is the active form of vitamin D?

1,25-dihydroxycholecalciferol (calcitriol) (correct)

Ergosterol

Cholecalciferol

7-dehydrocholesterol

What is the effect of calcitriol on the bone?

Promotes bone mineralization

Inhibits calcium absorption

Causes mobilization of calcium and phosphate from the bone (correct)

Increases bone demineralization

What is the main function of vitamin A in vision?

Forming rhodopsin Signup and view all the answers

What is the result of vitamin D deficiency in children?

Rickets Signup and view all the answers

What is the source of vitamin D?

7-dehydrocholesterol and ergosterol Signup and view all the answers

What is the dietary source of preformed vitamin A?

Animal tissues Signup and view all the answers

What is the effect of calcitriol on the intestine?

Increases the intestinal absorption of calcium and phosphate Signup and view all the answers

What is the site of absorption of vitamin A?

Intestine Signup and view all the answers

What is the form of vitamin A stored in the liver?

Retinyl palmitate Signup and view all the answers

What is the protein that transports vitamin A from the liver to peripheral tissues?

Retinol binding protein Signup and view all the answers

What is the antioxidant property of vitamin A attributed to?

Carotenoids Signup and view all the answers

What is the major deficiency disease associated with vitamin A deficiency?

All of the above Signup and view all the answers

What is the characteristic of vitamin A in epithelial cells?

Maintaining integrity Signup and view all the answers

What is the active form of Vitamin E?

α-tocopherol Signup and view all the answers

What is the primary function of Vitamin K in the body?

Coagulation of blood Signup and view all the answers

What is the consequence of Vitamin C deficiency?

Impaired synthesis of collagen Signup and view all the answers

What is the role of Vitamin K in bone growth and development?

Formation of bone matrix Signup and view all the answers

What is the function of Thiamine pyrophosphate in the body?

Cofactor for pyruvate dehydrogenase Signup and view all the answers

What is the primary function of Vitamin E in the body?

Antioxidant properties Signup and view all the answers

What is the consequence of Vitamin K deficiency?

Hemorrhagic disease Signup and view all the answers

Why can't humans synthesize Vitamin C?

Due to deficiency of L-gulonolactone oxidase Signup and view all the answers

What is the role of thiamine in energy metabolism?

Cofactor for α-ketoacids dehydrogenase Signup and view all the answers

What is the symptoms of Dry beriberi?

Peripheral neuropathy, muscle pain & tenderness Signup and view all the answers

What is the role of Flavin coenzymes?

Involved in fatty acid and amino acid oxidation and mitochondrial respiratory chain Signup and view all the answers

What is the symptoms of Riboflavin deficiency?

Glossitis, cheilosis, angular stomatitis Signup and view all the answers

What is the role of NAD+?

Important as a “hydrogen carrier” for ATP production Signup and view all the answers

What is the symptoms of Wernicke-Korsakoff syndrome?

Nystagmus, psychosis, dementia Signup and view all the answers

What is the active form of Vitamin B6?

Pyridoxal phosphate (PLP) Signup and view all the answers

Which vitamin is involved in the synthesis of fatty acid, cholesterol, and steroid hormones?

Vitamin B5 Signup and view all the answers

What is the result of a prolonged consumption of raw egg whites?

Vitamin B7 deficiency Signup and view all the answers

What is the symptom of Pellagra, a deficiency disease caused by lack of Vitamin B3?

Rough skin Signup and view all the answers

What is the role of Vitamin B6 in the body?

All of the above Signup and view all the answers

Which vitamin is involved in the synthesis of ketone bodies?

Vitamin B5 Signup and view all the answers

What is the consequence of untreated Vitamin B3 deficiency?

Death Signup and view all the answers

What is the symptom of Vitamin B5 deficiency?

Burning foot syndrome Signup and view all the answers

Study Notes

Vitamins

Vitamins are organic molecules essential for normal health and growth, required in trace amounts, and must be obtained from the diet.

Classification of Vitamins

Vitamins are classified into two main categories: fat-soluble vitamins and water-soluble vitamins.

Fat-Soluble Vitamins

Vitamin A

Occurs in two forms: preformed (active form) and provitamin A.
Found in animal and plant tissues, respectively.
Converted to retinoids form in the intestine.
Has a beta-ionone ring, which is essential for its function.
Functions: vision, reproduction, antioxidant, and growth.
Deficiency: night blindness, Bitot's spots, xerophthalmia, keratomalacia.

Vitamin D

Also known as the "sun-shine vitamin".
Derived from 7-dehydrocholesterol or ergosterol by UV radiation.
Active form: 1,25-dihydroxycholecalciferol (calcitriol).
Functions: promotes calcium and phosphate absorption in the intestine, bone mobilization, and kidney reabsorption.
Deficiency: rickets (children) and osteomalacia (adults).

Vitamin E

Exists in eight chemical forms: tocopherol and tocotrienol.
Active form: α-tocopherol.
Functions: prevents free radical damage to polyunsaturated fatty acids and reduces oxidative damage to LDLs.
Deficiency: hemolytic anemia, peripheral neuropathy, and increased risk of cardiovascular diseases.

Vitamin K

Exists in two natural forms: vitamin K1 (phylloquinone) and vitamin K2 (menaquinone).
Functions: necessary for coagulation of blood, bone growth, and development.
Deficiency: hemorrhagic disease and osteoporosis.

Water-Soluble Vitamins

Vitamin C (Ascorbic acid)

Most animals can synthesize ascorbic acid, but humans cannot due to a deficiency of L-gulonolactone oxidase.
Functions: hydroxylation of proline and lysine, antioxidant, enhances iron absorption, and role in tryptophan and tyrosine metabolism.
Deficiency: scurvy, characterized by bleeding gums, bruising, and poor wound healing.

Vitamin B1 (Thiamine)

Active form: thiamine pyrophosphate.
Functions: cofactor for pyruvate dehydrogenase, α-ketoglutarate dehydrogenase, and transketolase.
Deficiency: beriberi (wet and dry), Wernicke-Korsakoff syndrome.

Vitamin B2 (Riboflavin)

Active forms: flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD).
Functions: involved in mitochondrial respiratory chain, fatty acid and amino acid oxidation, and citric acid cycle.
Deficiency: glossitis, cheilosis, angular stomatitis, and corneal vascularization.

Vitamin B3 (Niacin)

Active forms: nicotinamide adenine dinucleotide (NAD+) and nicotinamide adenine dinucleotide phosphate (NADP+).
Functions: important for ATP production by the respiratory chain and biosynthetic reactions.
Deficiency: pellagra, characterized by dermatitis, diarrhea, and dementia.

Vitamin B7 (Biotin)

Acts as coenzyme for carboxylation reactions.
Deficiency: dermatitis, atrophic glossitis, hair loss, muscle pain, anorexia, and hallucinations.

Vitamin B5 (Pantothenic Acid)

Component of coenzyme A (CoA), which has numerous functions in carbohydrate, lipid, and amino acid metabolism.
Deficiency: burning foot syndrome, characterized by paresthesia, staggering gait, and sleep disturbances.

Vitamin B6 (Pyridoxine)

Exists naturally in three forms: pyridoxine, pyridoxal, and pyridoxamine.
Active form: pyridoxal phosphate (PLP).
Functions: cofactor for transamination, deamination, formation of cysteine from methionine, heme synthesis, and decarboxylation reactions.
Deficiency: neurological manifestations, including seizures, depression, confusion, and peripheral neuropathy.

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Description

Learn about the classification, functions, and deficiency diseases of vitamins, including vitamin B complex, in the context of medical biochemistry.