8 - Fat-soluble vitamins – chemical structure, metabolism and biochemical significance. Diseases caused by vitamin deficiencies and overloading.

sections

• vitamins needed for

• 2 types

• fat soluble vitamins

vitamins needed for

• health

• growth

• survival

2 types

• water soluble

• fat soluble

fat soluble vitamins

• E → Tocopherol

• D → Calciferol

• A

• K

• E → Tocopherol

• source - plant oils + green beans

• stored - adipose tissue

• role - antioxidant

• consists of - several tocopherols + packaged in chylomicrons

• exported by - liver in form VLDL

• Hypovitaminosis:

  • neurological disorder

  • fast skin aging

  • risk of atherosclerosis

• D → Calciferol

• steroid hormone like molecule

• role - regulates gene expression

• active form - calcitriol

• deficiency in children - rickets: soft bones, more prone to fractures

Vitamin A

Vitamin A Summary:

• Active form: Derived from β-carotene

• Forms:

  • Retinol – stored in liver

  • Retinal – involved in vision

  • Retinoic acid – regulates gene expression (organ growth, morphogenesis)

• Vision role:

  • Trans-retinol → oxidised & isomerised → 11-cis-retinal

  • 11-cis-retinal + opsin → rhodopsin

  • Light converts 11-cis to all-trans-retinal → triggers visual signal

• Deficiency (Hypovitaminosis A):

  • Night blindness

  • Dry eyes/skin

  • Delayed growth

  • Poor wound healing

Vitamin K

• role - maintain normal levels of blood clotting proteins

• forms:

  • k1 - green veg

  • k2 - intestinal bacteria

  • k3

• hypovitaminosis - haemorrhagic anaemia - new-borns

• hypervitaminosis:

  • erythrocyte damage

  • jaundice - new-borns

  • liver impairment