VITAMINS AND COENZYMES
, INTRODUCTION
• Are organic compounds required in the diet in small amounts for the maintenance
metabolic integrity that include:
Multiple biochemical reactions
Growth
Survival
Reproduction of the organism
• Most prominent function is to serve as a coenzymes (prosthetic groups) for enzymatic
• Deficiency causes a specific disease, which is cured or prevented only by restoring the
the diet.
• In diet, some are present as precursors called ‘provitamins’ which in the body are co
vitamins.
Classes of Vitamins
• Divided into two groups:
Fat soluble (Vitamins A, D, E & K)
Water soluble (Vitamin B complex and Vitamin C).
, Fat soluble vitamins
• Are a polar, hydrophobic molecule
• Have isoprene derivative
• Bile salts and fats are essential for their absorption
• Generally stored in liver- more likely to accumulate in the body hence more likely
hypervitaminosis
• Normally, excreted in faeces
• Are transported in the blood in lipoproteins or attached to specific binding proteins
Water soluble vitamins
• Are soluble in water
• Are easily absorbed
• Are not stored in the body (except vitamin B12) – lack of vitamins quickly lead to
diseases (hypovitaminosis or avitaminosis) – affecting mostly the skin, blood ce
nervous systems
• Have threshold for urinary excretion
, FAT SOLUBLE VITAMINS
a. VITAMIN A
• A group of compounds which exhibit Vitamin A activity (retinoids and carotenoids)
a. Retinoids - Are found in foods of animal origin and consist of:
retinol (Vitamin A alcohol)
retinal (Vitamin A aldehyde)
retinoic acid (Vitamin A acid)
• Retinal and retinoic acid are formed from retinol.
• Retinal and retinol are interconvertible.
• Retinoic acid cannot be converted to either retinal or retinol.
b. Carotenoids - found in plants
• comprise of carotenes and related compounds known as pro-vitamin A as they can
to yield retinaldehyde and thence retinol and retinoic acid.
, INTRODUCTION
• Are organic compounds required in the diet in small amounts for the maintenance
metabolic integrity that include:
Multiple biochemical reactions
Growth
Survival
Reproduction of the organism
• Most prominent function is to serve as a coenzymes (prosthetic groups) for enzymatic
• Deficiency causes a specific disease, which is cured or prevented only by restoring the
the diet.
• In diet, some are present as precursors called ‘provitamins’ which in the body are co
vitamins.
Classes of Vitamins
• Divided into two groups:
Fat soluble (Vitamins A, D, E & K)
Water soluble (Vitamin B complex and Vitamin C).
, Fat soluble vitamins
• Are a polar, hydrophobic molecule
• Have isoprene derivative
• Bile salts and fats are essential for their absorption
• Generally stored in liver- more likely to accumulate in the body hence more likely
hypervitaminosis
• Normally, excreted in faeces
• Are transported in the blood in lipoproteins or attached to specific binding proteins
Water soluble vitamins
• Are soluble in water
• Are easily absorbed
• Are not stored in the body (except vitamin B12) – lack of vitamins quickly lead to
diseases (hypovitaminosis or avitaminosis) – affecting mostly the skin, blood ce
nervous systems
• Have threshold for urinary excretion
, FAT SOLUBLE VITAMINS
a. VITAMIN A
• A group of compounds which exhibit Vitamin A activity (retinoids and carotenoids)
a. Retinoids - Are found in foods of animal origin and consist of:
retinol (Vitamin A alcohol)
retinal (Vitamin A aldehyde)
retinoic acid (Vitamin A acid)
• Retinal and retinoic acid are formed from retinol.
• Retinal and retinol are interconvertible.
• Retinoic acid cannot be converted to either retinal or retinol.
b. Carotenoids - found in plants
• comprise of carotenes and related compounds known as pro-vitamin A as they can
to yield retinaldehyde and thence retinol and retinoic acid.
