Lecture 2 - The Chemical Basis of Life Lavoisier...

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Unformatted text preview: The Chemical Basis of Life Lavoisier (1743-1794) - noted the relative chemical simplicity of the mineral world and contrasted this with the complexity of the plant and animal worlds The latter were composed of compounds rich in the elements carbon , hydrogen , oxygen , nitrogen , sulfur , and phosphorous ( the six most abundant elements in living systems ) Early 20th century biochemical investigations of glucose breakdown in yeast and animal muscle cells revealed remarkable chemical similarities Jacques Monod - What is true of E. coli is true of an elephant The current understanding that all organisms share a common evolutionary origin is based, in part, on our biochemical unity Biochemical Unity - the biochemical composition ( make-up ) of all organisms is astoundingly similar The Chemical Basis of Life Fewer than 30 of the more than 90 naturally occurring chemical elements are essential to all organisms Bulk elements shaded in orange are structural components of all cells and tissues and are required in the diet in gram quantities Trace elements shaded in yellow are required in much smaller quantities (<< a few milligrams ) Carbon Chemistry Chemistry of living organisms revolves around carbon Carbon accounts for more than half the dry weight of cells C can form single bonds with hydrogen atoms, and single and double bonds with oxygen and nitrogen atoms Of greatest signiFcance for biological systems is the ability of carbon to form very stable single bonds with up to four other carbon atoms Two carbon atoms can share two (or three) electron pairs, thus forming double (or triple) bonds The reason for this is that carbon, with an atomic number of 6, has a valency of 4, i.e. requires 4 electrons to Fll its outer shellvalency of 4, i....
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Lecture 2 - The Chemical Basis of Life Lavoisier...

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