Unit 3, Lesson 5

Lesson 5 - Ions

Student Performance Objectives
1. Define ion, cation and anion.
2. Define ionic bond, and show how an ionic bond forms.
3. Explain the relationship between the words ion, electrolyte, and mineral.
4. Describe a simple experiment to show that ions can carry an electrical current.
5. Explain the importance of unpaired electrons in the chemistry of the human body utilizing
    the terms: free radical and antioxidant.

Lesson Outline
A. Definitions
    1. Ion - charged particles (e.g., atoms or atomic groupings called radicals) having unequal numbers of         protons and electrons.
    2. Cation: examples - Na+, K+, Mg+2, Ca+, H+, OH-.
    3. Anion: examples - Cl-, HCO3-?, HPO4-2, and H2PO4-1
B. Formation through redox reactions (see below, Lesson 8, part B5)) and resultant attraction of 
    the oppositely charged ions forming the ionic bond - use Na and Cl as examples.      
C. Relationship of ions, electrolytes and minerals - an electrolyte is a solution that carries an 
    electrical current (such as the body fluids), but in more common usage, electrolytes are the 
    most commonly found and most important ions in human body tissues - sodium, potassium,
    calcium, magnesium, chloride, bicarbonate, and the phosphates. In nutritional jargon, the 
    commonly found ions/electrolytes are referred to as minerals. 
D. DEMONSTRATION: The point is to show the ability of charged particles in a solution, ions,
    to carry an electrical current. Using the "light apparatus" demonstrate the inability of 
    distilled water to carry an electrical current and light up the bulb. Then demonstrate the 
    inability of a glucose solution, which is unionized in water, to light up the bulb. Then 
    demonstrate the ability of a small amount of NaCl to light up the bulb and the ability of 
    increasing amounts of NaCl added to the solution to make the bulb light up even more
    intensely. 
E. Importance of unpaired electrons in chemical reactivity,
    1. Concept of free radicals and the body's defense against them as the Antioxidant 
        defense system. See http://www.healthchecksystems.com/antioxid.htm
        a. Natural generation of free radicals from the cellular energy generating 
            organelles - the mitochondria.
        b. Potentially damaging effects of free radicals on DNA, lipids, and proteins.
        c. Antioxidant defense system
            (1) Enzymes - e.g., superoxide dismutase (SOD), catalase
            (2) Cofactors - minerals like selenium, zinc, and manganese
            (3) Vitamins like ascorbic acid (Vitamin C) and the tocopherols (Vitamin E).
    2. Importance of free radicals in the killing mechanisms of the leucocytes.
    3. Importance of free radicals in the initial origin of life when there were no enzymes for 
        catalysis.