UNIT I
CHEMISTRY/BIOCHEMISTRY
I. CHEMISTRY: THE BASIS FOR LIFE
A. ELEMENTS
Almost everything around us can be broken down into simpler substances. These substances can be further broken down into other simpler substances. There is a point where substances can no longer be broken down into other substances while keeping their characteristic properties. These substances are called elements. There are currently 106 named elements (92 naturally occurring), but this number is increasing because more man made elements are being created in laboratories.
From these 92 naturally occurring elements, only 20 are necessary for life. Of these 20 life elements, 6 make up 99% of all living matter: Sulfur, Phosphorous, Oxygen, Nitrogen, Carbon and Hydrogen (SPONCH, pneumonic device). Living organisms still need the other 14 elements, but in smaller amounts.
An atom is the smallest indivisible unit of an element that still has the characteristic of the element. Two or more atoms......
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