Vitamins, Minerals and Coenzymes
Vitamins are organic micronutrients needed in small amounts; minerals are inorganic elements. This domain tests solubility classes, coenzyme forms, deficiency diseases and major mineral functions.
Core rules
- Fat-soluble vitamins A, D, E and K are stored in body fat and liver; water-soluble vitamins B and C are largely excreted and need regular intake.
- Coenzyme forms include thiamine → TPP, riboflavin → FAD/FMN, niacin → NAD/NADP, pantothenic acid → coenzyme A, pyridoxine → pyridoxal phosphate, and biotin for carboxylation.
- Vitamin A is needed for rhodopsin; deficiency causes night blindness and xerophthalmia.
- Vitamin D is made in skin from 7-dehydrocholesterol and regulates calcium; deficiency causes rickets in children.
- Vitamin C is needed for collagen hydroxylation and is an antioxidant; deficiency causes scurvy.
- Iron is in haemoglobin, iodine in thyroid hormones, calcium in bone and clotting, and zinc in many enzymes.
Worked example
A child has bow legs, delayed walking and softened bones. The likely diagnosis is rickets. Reasoning: inadequate vitamin D reduces intestinal calcium and phosphate absorption, so bone mineralisation fails and soft bone bends under weight. The preventive measure is vitamin D with adequate calcium and sunlight exposure, not extra vitamin C.
Traps that cost marks
Vitamin B12 contains cobalt, so it is not a mineral. Water-soluble vitamins are not stored in large amounts. Vitamin D can be synthesized in the body, but it still behaves as a vitamin when intake is inadequate. Do not confuse iodine deficiency goitre with iron deficiency anaemia.