BIOL203 Lesson 8

• Minerals


  Indestructible, came from the earth, no living organisms can synthesize them
• Major minerals in human diet


  • Na, Mg, P, S, Cl, K, Ca
• Trace minerals in human diet


  • F, Cr, Mn, Fe, Cu, Zn, Se, I
  • 25% of elements found on earth is required by human body
• Major minerals


  Abundant, >100 mg/day
• Trace minerals


  Less abundant, <100 mg/day
• Body fluid compartments

  • Intracellular fluid: within cells, usually high in K and P, accounts for approximately 2/3 of body's water
  • Extracellular fluid: includes intercellular and intravascular fluids
  • Intercellular (interstitial) fluid: between cells, usually high in Na and Cl; large component of extracellular fluid
  • Intravascular fluid: located within the CV system or lymphatic system
• Sources of minerals

  • Food
  • Tap water (hard vs soft)
  • Dietary supplements
• Bioavailability of minerals

  Affected by physiological needs, source (animal vs plant-based), combination of foods (in lumen of small intestine), amounts of other minerals consumed (Mg, Ca, Cu, Fe compete for absorption)
• Calcium(bone health)


  • Found in bones and teeth as hydroxyapatite crystals
  • Regulates neural communication and electrical signals
  • Continuously remodeled by osteoclasts and osteoblasts (calcium homeostasis); regulated by thyroid and parathyroid glands
• Calcium bioavailability ranges from 5% to 60-70% depending on source
• Estrogen decreases osteoclast activity over time; after menopause, no estrogen = increase in osteoclast activity
• Peak bone mass


  Highest attainable bone density, developed during first 3 decades of life
• Osteoporosis


  Severely low bone density, susceptible to fractures, caused by collapse of vertebrae
• Phosphorus(bone health)


  85% stored in bones as hydroxyapatite, 15% in intracellular fluid

  • Almost impossible to be P deficient as it is found in nearly everything we eat; consuming too much P and not enough Ca may cause calcium to leech out of teeth causing severe tooth decay
• Magnesium(bone health)


  • >50% found in bones, influences formation of hydroxyapatite crystals, found inside cells
• Magnesium in plants is associated with the green pigment chlorophyll: any deep green leafy vegetable is a great source of Mg
• High sodium intake is associated with activated blood pressure and cardiovascular disease
• Potassium


  95% found inside cells, crucial for fluid balance and neural communication
• Processed foods often lack potassium because cells are no longer intact
• Iron


  • Essential for formation of hemoglobin in red blood cells
  • Absorption regulated by ferritin (iron-storage protein) in intestinal cells
• Iron-deficiency anemia


  Most common nutrient deficiency, results from depletion of iron stores leading to low hemoglobin
• High-risk groups for iron deficiency include women, growing infants and children
• Iodide(energy metabolism)


  • Almost all absorbed iodide ends up in the thyroid gland, essential for synthesis of thyroid hormones
• Iodide deficiency diseases


  Goiter, cretinism, leading cause of mental impairment globally
• Chromium (energy metabolism)


  • Enhances ability of insulin to take up glucose, does not increase muscle mass or melt fat
• Zinc

  • Required by over 100 enzymes, deficiency severely impairs growth and development
• Selenium


  • Most powerful antioxidant, lowers probability of cancer, intake depends on geographic location
• Fluoride toxicity is called fluorosis, caused by too much fluoride in water distribution
• What is neural communication?


  Electric signals that open protein channels for calcium to flood into presynaptic neuron; without calcium, neurotransmitters cannot be released and neurons fail to communicate
• Consequences of falling blood calcium levels?

  Parathyroid glands secrete PTH --> stimulates activation of vitamin D in kidneys; PTH and vitamin D duo increases calcium reabsorption in kidneys and stimulates osteoclasts to break down bones; vitamin D also travels to small intestine and increases bioavailability of calcium
• Sodium (fluid balance and neural communication)


  Extracellular ions; crucial in fluid balance and nerve impulse transmission
• What are the steps of neural communication?

  1. Electrical signal is produced
  2. Calcium floods into presynaptic neuron
  3. Neurotransmitters are released into synaptic cleft
  4. Neurotransmitters bind to ion channels on postsynaptic membrane and Na floods into postsynaptic cell
  5. Neurotransmitters bind to receptor molecules and opens ligand-gated ion channel
• Bioavailability of iron: depends mostly on physiological needs, but also the typeof iron consumed (heme vs non-heme)
• Metalloenzymes: enzymes that contain one or more minerals as part of their structure
• Zinc, copper and selenium are essential elements that have an antioxidant function
• Osteoclasts degrade bone tissue, whereas osteoblasts build bone tissue