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Thursday, September 23, 2010

2.8 Some Important Chemical Concepts in Medicine

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2.8: Some Important Chemical Concepts in Medical Science (Update 21 October 2018)

 Reduction & Oxidation
Acidity & Alkalinity
 The Concept of Concentration in Body Fluids 
Reduction & Oxidation: Atoms of each element, whether the simplest building-block, like Hydrogen (H; Atomic Number AN 1) or the famous radioactive Radium (Ra; AN 88) exist most stably in the electrically neutral state. It means the number of 1-positive-charge (1+) protons in the neutral atom’s nucleus is equal to the number of 1-minus-charge (1-) electrons in its orbitals. 
  When a chemical element enters into chemical reaction with another element, there is a loss, or “giving up”, of electron(s) by one element's atom and a gain, or “picking up”, of electron(s) by the other element's atom.
  In the reaction that forms table salt, the electrically neutral atom Na gives up an electron (1 minus charge) to become Na+ (1+ charged ion) and the electrically neutral atom Cl picks up the electron to become Cl (1–minus electrically charged chloride ion). Then the Na+ attracts the Cl and we have electrically neutral molecule salt (NaCl) crystals.
We call “pick up” or gain of one or more electron(s) by an atom, a “reduction.” Why? Because the atom that picks up one or more electron(s) has its electrical charge reduced. For example, in the above reaction, Cl (chlorine) neutral atom, with electrical charge of zero, or 0, picks up 1 electron (a single negative charge) from a neutral Na (sodium) atom and becomes a chloride ion Cl; its charge is reduced from 0 to minus-1.
  The other side of the reaction, a neutral atom loses one or more of its outer orbital electrons and becomes more electro-positive is called “oxidation,” and the element that undergoes it is said to have been oxidized and the chemical that caused it is called "oxidant". In this reaction, a neutral Na atom loses its 1 outermost shell orbital electron and becomes 1+ sodium ion; it has undergone the opposite of reduction; it has been oxidized. Here the oxidant that grabs away the electron, itself getting reduced and causing the other chemical to get oxidized is the chlorine Cl neutral atom. Why "oxidation"? Because oxygen O is the most powerful at pulling away outer electrons from other chemicals; in the process it becomes the Oxide ion  (O–  ; double-minus electric charge). When an element or other chemical compound or particle pulls away electron(s) to itself, it is an oxidant.
   In our bodies, certain chemicals called “free radicals,” such as superoxide (O–  ) hydroxyl ions (OH ), nitric oxide, and LDL cholesterol oxide, contain an unpaired highly reactive electron in the outer part of the molecule. These radicals can harm the body cells because the unpaired electron attracts our body oxygen (oxidation) often reacting with important chemical bonds and causing damage that leads to coronary heart disease, to cancer, to eye cataract and, more generally, to cell death and then to your death. The antioxidants exert stronger pull on electrons than oxygen does, so they grab away these dangerous free radical electrons and prevent them from being picked up by oxygen or other important body chemical, and in so doing, the antioxidants protect our cells from the free radical damage. Vitamins C, E, A, and the mineral element selenium are prime antioxidants because they are super electron grabber-off-ers. 
  From a word meaning, it is ironic that the so-called antioxidants exert this protective effect by being more powerful oxidants than the oxygen molecule. Antioxidant refers to their competition with oxygen to grab off electrons.
Of the antioxidants that you could take for good health, vitamin C, ascorbic acid or ascorbate, is best because it has no toxic side effect, is inexpensive, tastes good and is naturally stored. A dose of two grams with meals is what I use to keep my good level of vitamin C. Other anti-oxidants are problematic: vitamin E in high dose may cause brain bleed; vitamin A and beta carotene in high dose caused more lung cancer in smokers, and selenium may be toxic at antioxidant dose.
Acidity & Alkalinity: Focus on H, the neutral Hydrogen atom. It has a nucleus with only 1 proton that gives the nucleus a 1+ electric charge, and the charge is balanced by a single, unpaired orbital electron (1-minus electric charge). When neutral H loses its electron, it consists of only a proton in nucleus, the H+ ion; and the definition of an acid is a substance that liberates H+ ions, into solutions. For example, hydrogen chloride (HCl) is acid because, in stomach juice, it liberates H+, the acetic acid in our bodies and in vinegar is acid because it liberates H+, and so on. Acids taste sour and color litmus red and if strong, burn skin. The degree of acidity is important for chemical reactions to go forward and thus important for life. So we need to measure acidity in fluids. Too high acid can ulcerate stomach lining and, worse, stop living processes. The symbol [H+] means the concentration used in expressing acidity as pH number. The pH is the negative log of the hydrogen ion [H+] concentration expressed as milliEquivalents (mEq) per liter to base 10, ie, pH = –log [H+] (minus 1 multiplied by log [H+]).  So, if the pH of a fluid = 1, its [H+] is 0.1 (10-1)mEq/L and, as pH increases in number, the [H+] decreases by a power of 10 (a unit logarithm). The usual expressed range of pH is 0 to 14. The extremes are pH = 0 is [H+] 100 , or 1 mEq/L (Very high-acid) and pH = 14 is [H+10-14 (Very low-acid; thus very high alkaline). For more, find “acid” or “base” of “acidity” in the later chapters and click 2.13c Acidity and Alkalinity of the Body


   The Concept of Concentration in Body Fluids
In dealing with nutrition and good health, the concentration of chemical in the blood comes up. In blood-test analyses, the metric system is used, eg, a cholesterol concentration is given in milligrams per one tenth liter (deciliter dL) of whole blood, blood plasma or blood serum. It is usually written mg/dL and may be referred to as mg%. In some cases, concentrations of nutrients like vitamins are much lower, and reported in micrograms (1 g = 1,000,000 micrograms) per dL, the Greek letter sounded “mu”, μg/dL. Even smaller concentrations are used for certain hormones, eg nanograms (1 g = 1,000,000,000 ngs) per ml, or even smaller, picograms (1 g equals 1,000,000,000,000 picograms) per ml or smaller, femtograms (1 gram = 1,000,000,000,000,000 femtograms). The units are not so important as long as you keep aware of each and as long as the comparisons of tests are in the same units. So speaking about the total cholesterol value, a cholesterol of 200 without even mentioning the unit is understood because, in the US, mg/dL are the said units and 100 to 300 is the range value.
  Another concentration concept that is used much is the mol (or decimal fraction of mol) per liter (m/l or m/L – and do not confuse it with “ml”, or milliliter). A mol of a substance is its atomic (in case of an element alone) or molecular (in case of chemical compound) weight in grams, and a blood test concentration of 1 mol per L is that weight in 1 liter of the fluid being tested. For example if you were measuring the metal lead (Plumbum Pb with atomic weight 207), a concentration of Pb in whole blood reported as 1 millimol per liter and written mM/L would mean 207 milligrams (mg) of lead (1000 mg = 1 gram) were dissolved in each 1 liter of whole blood. (Highly toxic lead level) 
  "Equivalent” as a unit of concentration is related to mol, often the same. The relationship between a mol and an equivalent depends on the electrical charge number of the ion (the number of electrons its neutral atom gains or loses in usual chemical reaction). An equivalent is a mol divided by the ion charge number. The neutral H atom has 1 electron to lose and then it becomes the H+ ion (electric charge 1+) so 1 equivalent of H is 1 mole of H. But magnesium has 2 electrons to lose and it becomes Mg2+ ion (electric charge 2+) so 1 equivalent of Mg2+ is 1/2 mole of Mg2+. It does not matter whether the electric charge is plus or minus. As with mols, equivalents take prefixes like milliequivalent (mEq) and so on. Equivalent is used with acids, bases and the electrolytes like Na+, K+, Cl-, HCO3-. In the European SI system measurements the Equivalent per liter has been done away with and only mol per liter is used. But in USA, and a few other countries the equivalent is retained.
        END OF CHAPTER. To read on now, click 2.9a Secrets of Healthy Food - the Carbohydrates









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