What are vitamins and co-enzymes ? Describe fat soluble vitamins with examples.

Vitamins and Co-enzymes: A Fundamental Distinction

Vitamins are classified as either fat-soluble or water-soluble, based on their solubility in fats or water. They are essential organic molecules that the body cannot synthesize in sufficient quantities and must obtain from the diet. They participate in numerous biochemical reactions, often acting as catalysts or regulators.

Co-enzymes are distinct from vitamins, though many vitamins *become* co-enzymes after metabolic activation. They assist enzymes in catalyzing reactions. Enzymes are biological catalysts, and co-enzymes enhance their activity. Co-enzymes are often derived from vitamins (e.g., Coenzyme A from Pantothenic acid, NAD+ from Niacin). They bind to the active site of enzymes, facilitating substrate binding and chemical transformations.

Fat-Soluble Vitamins: A Detailed Overview

Fat-soluble vitamins (A, D, E, and K) are absorbed along with dietary fats in the small intestine and are stored in the liver and fatty tissues. This storage capacity means deficiencies develop slowly, but also increases the risk of toxicity with excessive intake.

Vitamin A (Retinol)

• Sources: Liver, dairy products, eggs, fortified foods, and as beta-carotene (provitamin A) in orange and green leafy vegetables.
• Functions: Vision (especially night vision), cell growth and differentiation, immune function, reproduction.
• Deficiency: Night blindness, xerophthalmia (dry eyes), increased susceptibility to infections, impaired growth.
• Toxicity: Hypervitaminosis A – nausea, vomiting, headache, blurred vision, liver damage.

Vitamin D (Calciferol)

• Sources: Sunlight exposure (skin synthesis), fatty fish (salmon, tuna), egg yolks, fortified milk and cereals.
• Functions: Calcium absorption, bone health, immune function, cell growth.
• Deficiency: Rickets (in children), osteomalacia (in adults), increased risk of osteoporosis.
• Toxicity: Hypercalcemia (high blood calcium), nausea, weakness, kidney damage.

Vitamin E (Tocopherol)

• Sources: Vegetable oils (wheat germ oil, sunflower oil), nuts, seeds, green leafy vegetables.
• Functions: Antioxidant, protecting cell membranes from damage by free radicals, immune function.
• Deficiency: Rare, but can cause nerve damage, muscle weakness, and impaired immune function.
• Toxicity: Relatively non-toxic, but high doses may interfere with blood clotting.

Vitamin K (Phylloquinone & Menaquinone)

• Sources: Green leafy vegetables, broccoli, vegetable oils, synthesized by gut bacteria.
• Functions: Blood clotting, bone health.
• Deficiency: Bleeding disorders, impaired bone mineralization.
• Toxicity: Rare, but can interfere with anticoagulant medications.

Vitamin	Primary Function	Deficiency Symptoms	Toxicity Symptoms
Vitamin A	Vision, Cell Growth	Night Blindness, Xerophthalmia	Nausea, Liver Damage
Vitamin D	Calcium Absorption	Rickets, Osteomalacia	Hypercalcemia, Kidney Damage
Vitamin E	Antioxidant	Nerve Damage, Muscle Weakness	Interference with Blood Clotting
Vitamin K	Blood Clotting	Bleeding Disorders	Interference with Anticoagulants