1.Digestion, Nutrition & Bonds
Foodstuffs mainly consist of biopolymers (complex carbohydrates, proteins and lipids); large molecules made of monomers (sugars, amino acids and fatty acids/glycerol) linked together by chemical bonds. Bonds are of vital importance in living systems, as they are broken in digestion, to provide energy - they are exergonic reactions - and constructed in repair and growth - endergonic reactions - where the energy previously generated is harnessed.
CarbohydratesÃÂ®Monosaccharides ÃÂ®4 kcals g-1
ProteinsÃÂ®Amino Acids (AAs)ÃÂ®4 kcals g-1
LipidsÃÂ® Fatty Acids (FAs) and GlycerolÃÂ®9 kcals g-1
Whilst several bond classification systems exist the most important in physiology is the covalent bond; where two atoms 'share' outer shell electrons, making both more stable. This forms the basis of peptide; proteins, ester; fats and saccharide: carbohydrate, biopolymer backbones. The ionic bond; electrons are transferred between atoms comes a close second, they are key to the oxidation/reduction (redox) reactions, figure 1, of cellular energy generating systems whose activity is harnessed and then stored within adenosine triphosphate (ATP), (Houston, 2001).
They are also vital to the formation of ions within body fluids, e.g. Na+, Ca2+, Mg2+, Cl-, H+; all play a direct or indirect role in the energy generating pathways and in other vital areas, e.g. nerve conduction.
Table 1: The main Nutrients
Carbohydrates -Mostly in the form of complex carbohydrates (polysaccharides)
Proteins -Twenty amino acids are found in human proteins, only 12 of which can be produced in the body. The remaining eight are the essential amino acids and must be dietary supplied.
Lipids -Usually in the form of triglycerides, which become fatty acids (FAs) and glycerol
Minerals -There are twelve key minerals, which must by dietary supplied; Calcium, Magnesium, Phosphorous, Iron, Potassium, Zinc, Iodine, Copper, Molybdenum, Manganese, Chromium and Selenium.
Vitamins -Small organic molecules that facilitate...