Vitamins and Minerals Study Guide

COURSE OUTLINE

  • I. VITAMINS

    • A. Vitamin A (Retinol)

    • B. Vitamin D (Cholecalciferol)

    • C. Vitamin E (Tocopherol)

    • D. Vitamin K

    • E. Vitamin B1 (Thiamine)

    • F. Vitamin B2 (Riboflavin)

    • G. Vitamin B3 (Niacin)

    • H. Vitamin B5 (Pantothenic Acid)

    • I. Vitamin B6 (Pyridoxal phosphate)

    • J. Vitamin B7 (Biotin)

    • K. Vitamin B9 (Folic Acid)

    • L. Vitamin B12 (Cyanocobalamin)

    • M. Vitamin C (Ascorbic Acid)

  • II. MINERALS

    • A. Zinc

    • B. Calcium

    • C. Phosphorus

    • D. Sodium

    • E. Potassium

    • F. Iron

  • Reference(s):

    • Harvey, R. A., & Ferrier, D. R. (2017). Lippincott’s illustrated reviews: biochemistry. Lippincott Williams & Wilkins.

    • Dr. Viesta’s Powerpoint (2025). Vitamins and Minerals

VITAMINS

  • Definition:

    • Organic molecules, micronutrients, essential.

    • They are chemically unrelated compounds that cannot be synthesized in adequate quantities by humans.

    • They must be supplied by the diet.

  • Functions:

    • Aid in metabolism

    • Act as antioxidants

    • Essential for collagen synthesis

    • Important for the development of red blood cells (RBCs)

    • Serve as coenzymes (for instance, vitamin C is a precursor to coenzymes NAD, FAD).

WATER SOLUBLE VITAMINS

  • Examples:

    • Folic acid

    • Cobalamin (Vitamin B12)

    • Ascorbic acid (Vitamin C)

    • Pyridoxine (Vitamin B6)

    • Thiamine (Vitamin B1)

    • Niacin (Vitamin B3)

    • Riboflavin (Vitamin B2)

    • Biotin

    • Pantothenic acid

FAT SOLUBLE VITAMINS

  • Examples:

    • Vitamin A, D, E & K

VITAMIN A (RETINOL)

  • Recommended Dietary Allowance (RDA):

    • 750 ug

Sources:

  • Animal Sources:

    • Egg yolk, fish, liver, oil, milk

  • Plant Sources (Carotene):

    • Carrot, mango, papaya, green vegetables

Functions:

  • Vision

  • Growth and development

  • Tissue differentiation

  • Normal reproductive function

  • Maintain integrity of epithelial cells

  • Synthesis of glycoproteins

  • Antioxidants

Deficiency Symptoms:

  • Vision:

    • Loss of sensitivity to green light, decreased dark adaptation

  • Night Blindness (Nyctalopia):

    • Impairment of vision in the dark

  • Xerophthalmia:

    • Keratinization of conjunctiva and cornea

  • Bitot's Spots:

    • Grayish white plaques on conjunctiva

  • Keratomalacia:

    • Softening of the cornea, possible blindness

  • Others:

    • Follicular hyperkeratosis, increased susceptibility to infections, anemia

Toxic Manifestations:

  • Headache

  • Hepatomegaly

  • Hypercalcemia

  • Alopecia

  • Hyperlipidemia

  • Teratogenic effects

Chemistry:

  • Active Forms:

    • Retinol (vitamin A alcohol)

    • Retinal (vitamin A aldehyde)

    • Can be oxidized to retinoic acid (irreversible)

  • Structure:

    • Contains β-ionone rings, compounds with vitamin A activity are called retinoids

    • Major isomers exist, including all-trans-retinal (natural) and 11-cis-retinal (biologically critical for vision).

Absorption and Transport:

  • β-carotene is converted to retinal, then retinol in the intestinal mucosa.

  • Absorption requires dietary fats and bile salts; packaged in chylomicrons to be transported to the liver for storage as retinyl palmitate.

  • Retinol is released from the liver as trans-retinol bound to retinol-binding protein (RBP).

  • The retinol–RBP complex binds to possible receptors and acts in gene expression by interacting with retinoic acid-binding proteins (CRBP).

RHODOPSIN AND VISION:

  • Activation of Rhodopsin:

    • Composed of opsin and 11-cis-retinal.

    • Light causes conversion of 11-cis-retinal to all-trans-retinal, resulting in a nerve impulse sent to the brain.

    • Conformational changes lead to metarhodopsin II, stimulation of G-protein transducin, and activation of cGMP pathways.

Visual Cycle:

  • Retinol is transported to the retina; converted to 11-cis-retinol and 11-cis-retinal, forming rhodopsin.

  • Light activates the visual cycle, requiring Vitamin A for regeneration.

Comparison Table of Rods and Cones:

Feature

Rods

Cones

Function

Vision in dim light

Color vision, visual acuity

Location

Mostly peripheral retina

Concentrated in fovea

Pigment

Rhodopsin

Photopsins

Sensitivity

High

Low

Color Detection

No

Yes

Response Time

Slow

Fast

Vitamin A Dependence

High

Less affected

Clinical Deficiency Sign

Night blindness

Color vision defects

  • Clinical Consequences of Vitamin A Deficiency:

  • Increased dark adaptation time and night blindness occur as early symptoms; associated with Bitot’s spots, xerosis, keratinization.

VITAMIN D (CHOLECALCIFEROL)

  • Formation:

    • Derived from 7-dehydrocholesterol through UV radiation in skin, isomerizing to cholecalciferol (vitamin D3).

Activation and Function:

  1. Liver: Cholecalciferol → 25-hydroxycholecalciferol (Calcidiol) via 25-hydroxylase.

  2. Kidney: Converted to active form 1,25-dihydroxycholecalciferol (Calcitriol) via 1-α-hydroxylase regulated by PTH.

  3. Mechanism of Action:

  • Binds to Vitamin D receptor (VDR) and interacts with vitamin D response elements (VDRE) on DNA to regulate genes associated with calcium and phosphate homeostasis.

Biochemical Pathway of Vitamin D:

  • Skin synthesis through UV light, liver conversion, kidney activation, and roles in calcium homeostasis, with effects on absorption and mobilization of calcium and phosphate.

Regulatory Functions:

  • Enhances intestinal absorption of calcium and phosphate, supports bone mineralization alongside parathyroid hormone, and modulates immune functions.

Deficiency Effects:

  • Causes rickets in children, osteomalacia in adults, and may lead to hypocalcemia and other systemic implications.

VITAMIN E (TOCOPHEROL)

  • Acts as a lipid-soluble antioxidant, protecting membranes from oxidative damage.

  • Functions include stabilizing cell membranes and supporting immune function.

  • Deficiency: Rare; leads to neurological issues, hemolytic anemia, and peripheral neuropathy especially in preterm infants.

VITAMIN K

  • Refers to a group of naphthoquinone derivatives required for carboxylation of glutamic acid residues in proteins for proper blood coagulation.

  • Essential for coagulating proteins like prothrombin; regulates factors II, VII, IX, X.

  • Absorption: Requires bile salts typically occurs in the small intestine; transported by chylomicrons in circulation.

Summary of Functions of Minerals:

  • Minerals function as micronutrients, serve as building blocks for various physiological needs (bones, hemoglobin), and act as cofactors for enzymatic reactions necessary for metabolism and homeostasis.

  • Categorized into trace minerals, electrolytes, and ultratrace minerals with defined dietary requirements (e.g., calcium, phosphorus), each having specific metabolic roles.