Biology Chapter 2

Biology Chapter 2 - CHAPTER 2 THE CHEMICAL CONTEXT OF LIFE...

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CHAPTER 2 THE CHEMICAL CONTEXT OF LIFE I. Chemical Elements and Compounds A. Matter consists of chemical elements in pure form and in combinations called compounds Chemistry is fundamental to an understanding of life, because living organisms are made of matter. B. Life requires about 25 chemical elements Element = A substance that cannot be broken down into other substances by chemical reactions. - All matter is made of elements. - There are 92 naturally occurring elements. - They are designated by a symbol of one or two letters. About 25 of the 92 naturally occurring elements are essential to life. Biologically important elements include: C = carbon O = oxygen make up 96% of living matter H = hydrogen N = nitrogen Ca = calcium P = phosphorus K = potassium S = sulfur make up remaining 4% of an organism's weight Na = sodium Cl = chlorine Mg = magnesium Trace element = Element required by an organism in extremely minute quantities. -Though required by organisms in small quantity, they are indispensable for life - Examples: B, Cr, Co, Cu, F, I, Fe, Mn, Mo, Se, Si, Sn, V and Zn Elements can exist in combinations called compounds. -Compound = A pure substance composed of two or more elements combined in a fixed ratio. -Example: NaCI (sodium chloride) -Has unique emergent properties beyond those of
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Biology Chapter 2 - CHAPTER 2 THE CHEMICAL CONTEXT OF LIFE...

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